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Johannes Kepler's on the More Certain Fundamentals of Astrology Prague 1601Author(s): J. Bruce Brackenridge and Mary Ann RossiReviewed work(s):Source: Proceedings of the American Philosophical Society, Vol. 123, No. 2 (Apr. 27, 1979), pp.85-116Published by: American Philosophical SocietyStable URL: http://www.jstor.org/stable/986232 .Accessed: 07/11/2011 23:57

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JOHANNES KEPLER'S ON THE MORE CERTAIN FUNDAMENTALS OF ASTROLOGY

PRAGUE 1601

FOREWORD, NOTES, AND ANALYTICAL OUTLINE BY

J. BRUCE BRACKENRIDGE

NEWLY TRANSLATED FROM THE LATIN BY

MARY ANN ROSSI

FOREWORD

The Scientific Basis of Astrology

The traditional textbook in physics or astronomy views Johannes Kepler only with regard to his contributions to astronomy and, in particular, with regard to that limited portion of his astronomical works that has proved to be of continued utility: his three laws of planetary motion. If his astrological views are discussed at all, it is assumed that as an enlightened astronomer he believed astrology to be nonsense or at best a source of income forced on him by an unen- lightened patron. Such a view is not supported either by Kepler's writings or by the tradition of scientific astrology in which he worked. This tradition has roots that extend back to the earliest recorded scientific endeavors. In fact, Otto Neugebauer in his Exact Sciences in Antiquity makes a strong case for the claim that initially the fundamental doctrines of astrology were pure science.

To a modern scientist, an ancient astrological treatise appears as mere nonsense. But we should not forget that we must evaluate such doctrines against the contemporary background. To Greek philosophers and astronomers the universe was a well defined structure of directly related bodies. The concept of predictable influence between these bodies is in principle not at all different from any modern mechanistic theory. And it stands in sharpest contrast to the ideas either of arbitrary rulership of deities or of the possibility of influencing events by magical operations. Compared with the background of religion, magic, and mysticism, the fundamental doctrines of astrology are pure science. Of course, the boundaries between rational science and loose speculation were rapidly obliterated and astrological lore did not stem-but rather promoted- superstition and magical practices.'

This astrological boundary between rational science and loose speculation has been patrolled and defended by two outstanding astronomers: Claudius Ptolemy in the second century A.D., and Johannes Kepler in the seventeenth century A.D. Both these men see a purity in astronomy that does not exist in astrology, but the fundamentals of astrology, nevertheless, are defended as being well founded in science. In the introduction

to his great work on astrology, the Tetrabiblos, the astronomer Ptolemy clearly makes the distinction between the two disciplines: on the one hand, astronomy is concerned with observing, recording, and predicting the juxtapositions (aspects) of the celestial bodies with great scientific precision; on the other hand, astrology is concerned with applying the knowledge of the astronomical aspects to the less exact and more mundane task of predicting terrestrial events. Never- theless, both disciplines have in common a concern with the heavens, and both have a rational basis for their operation. Ptolemy states:

Of the means of prediction through [celestial observations] . . . two are the most important and valid. One, which is first both in order and in effectiveness is that whereby we apprehend the aspects of the movements of sun, moon, and stars in relation to each other and to the earth, as they occur from time to time [i.e., astronomy]; the second is that in which by means of the natural character of these aspects themselves we investigate the changes which they bring about in that which they surround [i.e., astrology]. The first of these . . . has been expounded to you as best we could in its own treatise (the Almagest) by the method of demonstration. We shall now give an account of the second and less sufficient method in a properly philosophical way, so that the one whose aim is the truth might never compare its perceptions with the sureness of the first, unvarying science, for he ascribes to it [astrology] the weakness and unpredictability of material qualities found in individual things nor yet refrain from such investigation as is within the bounds of possibility, when it is so evident that most events of a general nature draw their causes from the enveloping heavens.2

Ptolemy continues by saying that although "alle- gations against the first can only be made by the blind" and that "there are spacious grounds for those leveled at the second," nevertheless he intends to examine "the measure of both the possibility and usefulness of such prognostication." After all, he reminds us, "everything that is hard to obtain is easily assailed."

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Astrology is concerned with events in the world of flux that exists below the lunar sphere while astronomy is concerned with events in the universe of per- fection that exists beyond the lunar sphere. For Ptolemy, as for Aristotle, these are two separate and distinct entities. Nevertheless, there is a link between them. Aristotle, in On Comning into Being and Passing Away, gives the approach and recession of the sun as the formal cause for the origin of all movement, generation, and corruption on earth. Ptolemy also begins his defense of the link between celestial and terrestrial events by considering the obvious influence of the sun (ask any farmer) and of the moon (ask any sailor). Further, the stars can predict important meteorological phenomena (each year when the dog star Sirius rises with the sun, the Nile floods). And then he addresses the more complex but equally important question of aspects or juxtapositions of the planets. Unlike astronomy with its ability to make precise predictions of celestial events, there are limits to the ability of astrology to make accurate predictions of terrestrial events. But Ptolemy says, "It would not be fitting to dismiss all prognostications of this character because it can sometimes be mistaken, for we do not discredit the art of the pilot for its many errors."

Although Newton did not believe gravity to be an "innate, essential and inherent property of matter," nevertheless for eighteenth-century "Newtonians" gravitation and mathematical physics combined to offer the ultimate and final explanations for all the subtleties of celestial motion that the astronomer could observe. At the end of the eighteenth century the goal of LaPlace's great work on astronomy was "to reduce all the known phenomena of the system of the world to the law of gravity, by strict mathematical principles, and to complete the investigations of the motions of planets, satellites, and comets, begun by Newton in his Principia." 3 He appeared to accomplish this task. There was, however, no successful application of gravitational theory to astrology. The gravitational influence of planets on terrestrial objects was too weak and too complex to lend itself to the type of mathematical analysis that proved so successful for astronomy. The two disciplines now clearly must go their separate ways.

But neither Ptolemy in the second century nor Kepler in the seventeenth century had to grapple with the mysticism of that occult force, gravitation. The origin of the tradition in which Ptolemy operated can be traced back to Plato. In the sixth century A.D.

commentary on astronomy, Simplicius formulated the Platonic tradition of the fourth century B.C. as follows:

Plato lays down the principle that the heavenly bodies' motion is circular, uniform, and constantly regular. There- upon he sets the mathematicians the following problem: What circular motions, uniform and perfectly regular are

to be admitted as hypotheses so that it might be possible to save the appearances presented by the planets?4

The first response to this charge was by Plato's contemporary Eudoxus, who proposed a nest of twenty- six homocentric spheres: one sphere for the motion of the stars, two spheres for the sun, three for the moon, and four for the five planets. Aristotle objected to this system on the ground that, as a mathematical formulation, it served only as a calculating device. He sought a system that represented in physical fact the mechanism of celestial motion. In such a physical system the motions of each set of spheres would inter- act with each of the other sets, and additional spheres would be required to "roll back" the motion of those spheres preceding it. This mechanical system of nested spheres requires fifty-five spheres in all.

Whatever homocentric system was elected, it was in effect a combination of circular motions, all centered about the earth. The next major refinement in technical astronomy was the introduction of the epicycle by Hipparchus in the second century B.C. In an epicycle a planet revolves in a circle whose center is a point in space; this point itself revolves in a circle whose center is the earth. If the periods of the two motions, that of the planetary circle called the epicycle and that of the center of the epicycle called the deferent, are equal and opposite, the result is simply motion on a simple circle eccentric to the earth. If the periods are not the same, more complex motions can be obtained. Ptolemy, in the second century A.D., carried this technical, mathematical analysis of circular motion to its fruition by combining eccentric and epicyclic motions and by adding yet a third variation, the equant; this device controls the speed of the center of the epicycle on the deferent by making it uniform but with respect to yet a third point, which is neither the earth nor the center of the deferent. The system does violence to Plato's charge of uniform motion, at least with respect to the earth, but it continues in the tradition of per- fect celestial circularity. Further, though it is complicated, nevertheless it is capable of saving the phenomena. Not until Kepler's New Astronomy was published in 1609 could any system compare to it.

The popular belief that Copernicus' heliocentric system constitutes a significant simplification of the Ptolemaic system is obviously wrong. The choice of the reference system has no effect whatever on the structure of the model, and the Copernican models themselves require about twice as many circles as Ptolemaic models and are far less elegant and adaptable. In fact, the importance of Copernicus' work lies in a totally different direction than generally announced.5

What is important for us to note is that neither Ptolemy nor Copernicus makes any reference to what may be called the "physical causes." It is in the nature of a celestial object, such as a planet, to move in a circle, just as it is in the nature of a terrestrial

86 [PROC. AMER. PHIL. SOC.

KEPLER ON ASTROLOGY

object, such as a falling stone, to move in a rectilinear fashion toward its "natural place." Since such a natural and geometric explanation is sufficient for astronomical phenomena, it is equally natural, and thus equally scientific, for geometry to explain astrological phenomena. Given the astrological powers of the luminaries and planets from their juxtaposition (see Note 18), the nature and order of the constellations in the Zodiac from tradition, and the motions and juxtapositions of the planets from astronomy, Ptolemy may make some logical and scientific attempt to predict the "established influence" of celestial bodies on terrestrial events.

By the beginning of the seventeeth century, however, the situation was changed. Copernicus' work, despite having been forced into complex Ptolemaic-like convolutions in order to predict detailed planetary motions, suggested certain overall simplifications. More- over, the great Danish practical astronomer, Tycho Brahe, had amassed celestial data far superior to Ptolemy's (2" of arc contrasted to Ptolemy's 10"). Finally, the English physician William Gilbert had written a book, On Magnets, in which he discussed the earth's magnetic efflux and analyzed its ability to attract and repel lodestones. All three authors are mentioned in Kepler's great survey and review of his work The Epitome: "I build my whole astronomy upon Copernicus' hypotheses concerning the world, upon the observations of Tycho Brahe, and lastly upon the Englishman William Gilbert's philosophy of magnetism." 6

It is understandable that he would heed the work of Copernicus and Tycho, but of what interest is terrestrial magnetism in a work devoted to celestial motion? Even though Copernicus had attempted to shift the center of celestial circular motion, nevertheless he maintained the Platonic and Aristotelian tradition of natural celestial circularity. Celestial bodies move as they move because it is in their nature to move that way. A careful analysis of Tycho's data for Mars forced Kepler to break with the tradition of planetary circles and to replace them with ellipses. But of equal interest is Kepler's concern with "physical causes." He recognizes that there are irregularities in the paths of planets (i.e., they do not move uniformly in circles, but rather the radius varies in distance as prescribed by the law of elliptical paths, and the speed varies as prescribed by the law of equal areas in equal times); he accordingly describes a physical mechanism by which the supposed magnetic efflux of the rotating sun sweeps the planets around in their orbits. Further, since Kepler's sun is essentially a magnetic monopole and the planet a magnetic dipole of fixed inclination, he can account for variations in the radius of the path because the planet is attracted or repulsed as it changes its relative magnetic orienta- tion with respect to the sun. It is not important here,

however, to understand or to evaluate the mechanisms; what is important to note is Kepler's feeling that he should attempt such a physical analysis.

Before one makes an eighteenth century Newtonian of Kepler, however, it is well to consider his devotion to the other and more traditional causes in astronomy: the geometric tradition that had to this time served the astronomer so well. Certainly in his earlier work The Cosmographic Mystery (see Note 29) and in his later work The Harmonies of the World (see Note 30) he sings the praises of God and Geometer and of the mysteries and order revealed through this means alone. Even in the Epitome itself the supremacy of geometrical causes can be found:

Then you evaluate the density of the lunar body as pro- portioned to twelve lunar revolutions in one year: what will you say is the archetypal cause of this number? The cause seems to be composite of geometrical beauty and of the office of this planet in the world as follows: For the moon is a secondary planet assigned to the Earth, and it keeps to its own private course around the Earth. But 360 revolutions were allotted to the Earth, while the centre of the Earth makes one return around the sun. Then, just as among the upper planets, the sphere of the moon had to be a mean proportional between the body of the Earth and the sphere wherein the centre of the Earth really revolves, but the sun apparently; so also the revolutions of the moon had to be more than one but fewer than 360. And indeed the mean proportional between 1 and 361 is 19; but because the number 361 is not 360 and because 19 does not have any beauty either geometrical or harmonical; then the two numbers nearest to 19, which when multiplied together, give 360 and are the most beautiful geometrically and harmonically, should be chosen. Now the nearest numbers which give 360 are 18 and 20, because the first is smaller by unity alone, and the second greater than 19 by unity alone. But there is no demonstration of a figure of 18 sides. The numbers following nearest are 15 and 24, which also give 360. Now there are geometrical demonstrations of them, but rather worthless ones; nor do they give any outstanding ratio, but only the ratio between 5 and 8; nor are they the most excellent and first of all in harmonics. But the numbers 12 and 30-for there are no others nearer which give 360-excel in all ways; both geometrically, as being generated from the first figures inscribed in the circle, and harmonically, because all harmonies are represented by these two divisions of the string. Then of the numbers which, when multiplied together, give 360, there are none more beautiful.7

It is with this mixed background of physical and geometrical explanations of astronomical causes that Kepler approaches his analysis of astrology. In the best tradition of Ptolemy he seeks to protect its borders from those who, in Neugebauer's words, would obliterate "the boundaries between rational science and loose speculation." Kepler's title On the More Certain Fundamentals of Astrology attests to this concern and illustrates his belief that such fundamentals exist. The modern astronomer associates astrology with magic and mysticism, while accepting astronomy as a science. Kepler, however, like

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Ptolemy, views astrology as the profane, utilitarian, and less exact facet of that same activity of which astronomy is the sacred, abstract, and exact science. Unlike the modern astronomer, it was natural for Kep- ler to take astrology seriously.

Consequently he was concerned in this work to set forth clearly both the possibilities of astrology and its limitations. Before making the actual predictions for the year 1602, he introduces the more certain fundamentals of the science. The first to be discussed, though not necessarily the most important, are the physical causes, much in the same fashion as they are introduced into his astronomical works. The sources of the physical causes are the sun, the moon, and the planets; and the physical mechanism is the light that comes down from each. The traditional astrological powers of each planet must be retained (i.e., Mars is hot and dry as evidenced by its history of successful astrological usage), but the reasons for such powers must be revised. Previously the powers arose from the juxtaposition of the planet to the sun and the moon; now, with Kepler's adoption of the Copernican system, these juxtapositions have changed (see Note 18). The powers are derived instead from a consideration of the optical properties of each planet.

The discussion of the physical causes is followed in Thesis 36 by "another cause, which pertains equally to all planets, nobler by far than those mentioned earlier, and one possessing far more wonder." This is the geometric cause, whose source lies chiefly in the traditional five aspects of astrology augmented by the three new aspects suggested by Kepler (see Note 31). The receptor of such influences is an animate faculty, which is likened to a fourth type of soul (see Note 32). But not all of the traditional geometric causes of astronomy are accepted. The signs of the Zodiac are treated with contempt. In Thesis 49 Kepler states, "But nothing is more intolerable in this almost unique concern of astrologers than that they distribute with a certain infantile credulity twelve houses among seven planets beyond every sound and philosophical reason."

The predictions that follow comprise a month by month forecast of the weather for the year 1602 (in the best tradition of the Farmer's Almanac). When questions concerning predictions of crops are posed, he replies in Thesis 65: "The stuff of empty dreams are those divisions assigned by astrologers to grain, oil, corn, etc., according to the dispositions of the cardinal configuration of Jupiter. Do you want to know why wine has not turned out well this year? Because the year has been cold and humid. Whoever has made this observation has understood the effect from this cause alone."

The work concludes with a discussion of four major aspects of special significance in 1602, and with an invitation to all who think his fundamentals worthy

of consideration, to join with him in a discussion in order that the truth may be discovered.

It is tempting to see Kepler and his three laws of planetary motion in the guise of modern astronomy. In the final analysis, however, Kepler remains a man of his own time. His approach to astrology is changing in the same way that his approach to astronomy is changing. But by no means does he reject the science of astrology as does a modern astronomer. As Gerard Simon puts it:

We see clearly here what, with Kepler, is changing in western culture although he was not in a position to state it explicitly: the possibility of describing a causal process has become the criterion of rationality, and outside it there is no intellectual salvation. When he under- took to make astrology healthy, he thus imposed the modern demand of causal determinism on archaic con- ceptions which had grown out of the demands of a quite different kind of reasoning. The remedy was clearly one of those which in the end will kill the patient.8

For Kepler, there was no need to discard astrology. Quite the contrary, what was needed was a clear formulation of the foundations of astrology; of these he was certain.

TRANSLATOR'S PREFACE

My training is in the classical languages and civiliza- tion while that of my husband, Bruce Brackenridge, was initially in classical physics and more recently has been in the history of science. Since I know very little astronomy and he knows very little Latin, this translation was done in the best "Jack Spratt" tradition. I would offer the possible English translations that a section would allow and he would select that which made the best physical sense or would sug- gest compromises that would send me back to the Latin for a reappraisal. It was my charge to defend the dignity of the Latin and his to defend the integrity of Kepler.

We began this hybrid venture in London early in 1975 when I was a Reader in Classical Studies at Birkbeck College in the University of London and teaching Greek, Latin, and Renaissance Latin in the City Literary Institute. At the same time he was an academic visitor in the Department of History of Science at Imperial College in the University of Lon- don and teaching at the London branch of Lawrence University. The motivation for beginning the translation was a course in astronomy and astrology that my husband was scheduled to teach. The English translation of the Tetrabiblos, the astrological com- panion for Ptolemy's astronomical work, the Almagest, was readily available in the Loeb edition. The equiv- alent astrological work of Kepler, On The More Certain Fundamentals of Astrology, had been translated into English, and had been published in 1942 by Clancy Publications of New York, but it had long been out


KEPLER ON ASTROLOGY

of print and, in fact, a search of five of the major libraries of London failed to produce a copy. Thus, with the invaluable aid of one colleague and with the encouragement of others, the task was begun early in the spring, and the first draft was completed by mid- summer of 1975 for use by the students in London during the summer term.

Upon our return to Appleton, Wisconsin, this translation was again used in a class during the spring term of 1976. During this term, we also obtained a copy of the New York translation that was published in 1942. We found that the latter was lacking a translation of the dedication and adequate explanatory notes. More important, we thought that the English rendition was unsatisfactory because at times it was inaccurate in its translation and often incorrect in its interpretation. Moreover, after two classroom experiences with the original London translation, we found that it was also subject to some of the same criticisms that we had leveled at the New York translation. Thus, in the summer of 1976, we decided, with the aid of the two translations now in our possession, to try once again. The result is this translation, which we shall call the Appleton edition.

The major source, of course, is the original Latin edition, published by Kepler in Prague late in the year, 1601. It was only one of the many major pub-

lications of Kepler, the first being the Cosmographic Mystery in 1596 and the last being the Rudolphine Tables in 1630, the year of his death. In the interim he wrote twenty other major works, generally in Latin, but sometimes in German. These original works are now quite rare and often difficult to obtain, but fortunately two editions of the collected works have been printed. The first 9 was published in the nineteenth century and has recently been reprinted. The second,10 the one used for this translation, was begun early in the twentieth century (1938). Bibli- ographical references both to the original works and to the English translations may be found in an English translation of the German biography of Kepler by Max Casper 1 and in a biographical article on Kepler by Owen Gingerich.12

In this translation I have used brackets [] to indicate words added for explanation or clarification; the capitalization, punctuation, and paragraphing have been accommodated to modern usage. We have added an analytical outline that divides the work into three major sections, each with subsections and explanatory headings. There is indeed a risk in imposing such a structure, but it may provide an aid to the person who reads the work for the first time.

We commend this little work to your reading and hope that it brings some measure of joy to you.

ON THE MORE CERTAIN FUNDAMENTALS OF ASTROLOGY

A NEW BRIEF DISSERTATION REGARDING COSMIC THEORY WITH A PHYSICAL PROGNOSIS OF THE COMING YEAR 1602 A.D.

WRITTEN FOR PHILOSOPHERS

by M. JOHANNES KEPLER

Mathematician

Men, tell the power of the heavens; the known may be put to our profit; While in a field unexplored, you can see no gain or profit.

Labor resides in defeat, whereas victory will benefit richly, Nature's power do reveal, O Mankind, by your wit.

at Prague, Schuma

TO MY MOST ILLUSTRIOUS MASTER, LORD PETRUS WOK DE ROSENBERGK, IN KRUMLOV, BOHEMIA AND TO THE MASTER OF THE NOT UNRENOWNED HOUSE OF THE ROSENBERGKS, THE COUNSELOR OF HIS HOLY AND IMPERIAL MAJESTY, MY LORD CLEMENT:

ANALYTICAL OUTLINE

Title Page Dedication

Thesis Introduction ..................... .............. 1, 2, 3 Section One: On Physical Causes ......................... 4

A. The Sun ........................................ 5 1. The time of elevation........................... 6 2. The nature of the atmosphere ................. 7, 8

3. The obliquity of the sun's rays ................... 9 4. The numerical evaluation ................... 10, 11 5. The heat capacity of the earth............ 12, 13, 14

B. The M oon.............................15, 16, 17, 18 C. The Planets ................... .................. 19

1. The faculties of light ........................20, 21 2. The combinations of faculties .................... 22 3. The combinations assigned to planets .........23, 24 4. The physical cause of planetary differences ........25

a. Reflected light ........................26, 27, 28 b. Radiated light ...........................29, 30

5. The application of planetary properties to the making of predictions..............31, 32, 33, 34

D. A Summary of the Physical Causes .................35 Section Two: On Geometrical Causes .................36, 37

A . A spects ......... ...............................38 1. The Animate Faculty introduced ....... 39, 40, 41, 42 2. The Animate Faculty discussed by analogy........ 43

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3. Individual planetary influences on aspects.........44 B. Cycles ....................................45, 46, 47 C. Harmonic Motions of the Planets ...................48 D. Other Conjectured Causes . ............. 49, 50, 51

Section Three: On Predictions for 1602..................... A. The Weather for the Year 1602 ................. 52-62 B. On Eclipses ...................................63, 64 C. On Crops ......... ...........................65, 66 D. On Illness ......................................67 E. On Political and Military Matters ..............68, 69 F. On Earthquakes ..................................70 G. On Four Major Aspects of Special Significance

in 1603 ............................ 71, 72, 73, 74, 75 Conclusion

In Book I of his work On Duties, Cicero points out very clearly: "It is the mark of a great mind, and there have been many, even in a rather busy life, either to investigate or to try to investigate certain great questions, and to hold themselves within the bounds of their own fields." Applying this opinion of Cicero's especially to the study of astronomy, our Reinhold urges honest intellects not to allow themselves to be deterred from the study of astronomy by the judgments of those unlearned people who ad- mire only profitable skills. For, since these are studies of virtue, one requires fortitude in cultivating them, and this fortitude makes minds resolute against the foolish opinions of the crowd and scorns false judgments.

What this excellent man has said about each part of astrology, I thought that I might set forth at this time especially from another standpoint, that of p'hysics. People who write prognostics as a service ought to despise, especially in their inmost heart, two conflicting inclinations of the crowd and ought to fortify themselves against two characteristics of a shal- low and contemptible mind: desire for glory, and fear. For, although popular demand [for prognostics] is great, it is the mark of a corrupt mind in order to curry the favor of the crowd or for vainglory either to profess those things that nature does not exhibit, or to conceal the genuine miracles of nature, if one does not consider the more serious causes.

On the other hand are those who say that it is not fitting for a serious and philosophical person to prostitute the reputation of one's talents and the honor of one's erudition in matters debased by the very trivial and very empty daily soothsayings; by furnishing this divining, one feeds the curiosity of the crowd and kindles the superstitions of weak dispositions as if with a tinder. I confess that these objections are put forward with great cogency and that they are sufficient to deter the honest person, if there are not more serious reasons, from this kind of writing.

But if the desire to enlighten himself suffices as a person's motive (and such motives are approved for their own sake by wise men), then he cannot be stopped, unless in his timid concern about rumors and

in his fear of a bad reputation, he allows himself to be deterred from his purpose by these outside influences and approaching obstacles. For even if a great number of precepts are taken up with the trifles of the Arabs in this field, still those things that are in this hidden art of nature are not on that account trifles, nor should they be rejected as trifles.

But gems must be gathered from the mire; the honor of God must be set off by the proposed con- templation of nature, others must be attracted by example; and we must turn our attention and bend every effort to bring to light from the shadows of ignorance those matters that once served as a distinct advantage to the human race. And even if the out- come does not appear clear immediately and there is great uncertainty in the predictions because of the complexity of so many causes, nevertheless, one must strive all the more, since in work alone may virtue be observed.

As to the fact that many indeed abuse these [predictions] for their own curiosity, and confirm their own superstitions, I am not deterred any more by this than a good commander is deterred from attack- ing a city (and I pass over innumerable examples) by the loss of a few soldiers (whom, if one could, one would surely want saved).

If people have reservations about the publication of astrological matters for the general public, in whom there is slight hope of fruition, I should like them to consider that we may not reach the learned lying hidden here and there by any other means than a public one.

Add to this that here the same method may be observed in cultivating the curiosity of the crowd that is observed by doctors in regard to a sick person, so that we exploit the inordinate and pernicious desires of the crowd in order to administer warnings (as if some medication), veiled in the guise of prognostications, which serve to cure the disease of the mind, warnings of such a kind that we could hardly administer them in any other way. Therefore, just as doctors dealing with a sick person are not mad because they fall in with a delirious invalid by disguis- ing the voice and falsifying appearances in order to administer medicines, just so do I hope that those listening to me in good faith will suspect nothing sinister, because it is with the best intentions that I speak openly about the future to the crowd, who are eager to learn of new and future events. Those judgments are unfair that ridicule and never pursue the question of the greatest worth; in order not to leave these rather lowly services of life neglected and open to ridicule, take up [this book], so that, as he [Cicero] has enjoined, I may rescue the mentally blind.

Most illustrious Lord, I especially wished to dedi- cate to Your Highness as a New Year's gift, these


KEPLER ON ASTROLOGY

meditations of mine about the coming year, because I am convinced that Your Highness and all learned persons have been disposed to look with favor upon the cultivators of these arts in particular, which you have clearly shown by your words and especially by taking into your friendship that most renowned man of great nobility, Tycho Brahe, phoenix of astronomers. Then at his death, this [friendship] was offered to me as well with a declaration of your sorrow at his loss. And further you daily give evidence of your interest, since you entertain in your court that very famous man, D. Hermann Bulder, Doctor of Medicine, a very dedicated mathematician and a very learned man in this field; and you engage this gentleman in daily discussions about these matters.

Accept, then, most Illustrious Lord, these physical conjectures, and compare them with those political conjectures (which I refer to very frequently), which the dignity of your rank and your concern for the State will furnish. For only those who deal with the public interest will judge most accurately the fate of this prognosis; professors of Philosophy will surely lay claim to the philosophical and physical paradoxes for their own use and for their own criticism.

Farewell. May you enjoy a long and pleasant old age, and may you have a very Happy New Year. May Your Highness regard me as committed to your service.

M. JOH. KEPLER Mathematician

INTRODUCTION

Thesis 1

It is commonly considered the duty of the mathematician to write annual prognostics. Since, therefore, I have decided to fulfill this obligation for the coming year 1602 from the birth of Christ Savior by confining them [the prognostics] not so much to the curiosity of the public as to the duty of the philosopher, I shall begin with the principal prognostic that can be cited with the utmost safety: that this year there will be. a rich harvest of prognostics, since, owing to increasing popular demand, more authors are adding daily to their number.

Thesis 2

In those pamphlets some matters will be foretold which the event will make credible; but many more will be foretold which time and experience will refute as false and worthless. The latter will be written on the winds, the former very deeply inscribed in the memory, as is the way of the world.

SECTION ONE: ON PHYSICAL CAUSES

[There are three major sources of physical causes: the sun, the moon, and the planets. Light is the primary

mechanism by which they exert their influence: reflected light humidifies and radiated light heats.]

Thesis 3

And indeed, as the cause, so is the effect. Truly astrologers consider as causes of their predictions, to be sure, some that are physical, and some that are political, but when they yield the pen to enthusiasm, [they consider causes that are] in greater part inade- quate, for the most part imaginary, foolish, and false, and finally altogether worthless. If they sometimes speak the truth when they are carried away by their enthusiasm, it ought to be marked up to good luck, and it must not be thought that it issues, more often and for the most part, from some higher and occult instinct.

Thesis 4

Some physical causes are known by everyone, others, by very few; moreover, many things indeed exist naturally, but from causes comprehended by no one to this day. And of the causes that we consider to be known, there are some whose kind and explanation we all understand in common; there are others whose kind, or related causes, either very few understand, or no one at all.

A. THE SUN [The physical function of the sun is to heat. Its effectiveness is influenced by three factors: the time of elevation, the nature of the atmosphere, and the angle at which the sun's rays strike the horizon. Fur- ther, one must consider the heat capacity of the earth itself.]

Thesis 5

The most general, most powerful, and most certain cause, which is known to everyone, is that of the approach and withdrawal of the sun. This [cause], then, brings about the winter solstice around the birthday of Christ, the 21st of December, a bit before 6:00 P.M., and the summer solstice on the 21st of June at 10:30 at night. The former will then be [the cause of] the winter cold, and the latter, [the cause of] the summer heat.

[1. The time of elevation.]

Thesis 6

The working of this cause is evident from the following facts. At Prague, Bohemia, the altitude of the pole is 50o5'45". Now the inclination of the ecliptic in this century is 23?31'30", as observed by Tycho Brahe, that phoenix of astronomers, whom we have recently lost. Thus the sun, the source of our heat, shines in winter not more than 7 hours and 49 minutes above the horizon, and so it heats our air for a brief time, but lying more completely hidden below the horizon, it stops giving heat for [about] twice the time. On the other hand in the summer, the sun remains for 16 hours and 22 minutes above the horizon

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and continues to give heat, and it ceases from this operation for less than half the time.13

[2. The measure of the atmosphere.]

Thesis 7

But our air, as well as both water and earth (insofar as it is an element), unless continuously heated, return at once to their natural condition and grow cold. For that [teaching] of Aristotle's, that the nature of air is warm per se, is false.

Thesis 8

For whatever partakes of matter, insofar as it partakes of it, is by nature cold. But whatever is warm by its own power possesses that nature from an animate force that is either implanted or generated.

[3. The obliquity of the sun's rays.]

Thesis 9

Another and more powerful reason why the sun warms more when it is high than when it is low is this: that the low sun strikes our horizon obliquely and weakly, but the high sun [strikes] more at a right angle, and more strongly. No one thus far has been able to explain the reason why the immaterial ray of the sun behaves here in the same way that dense and material bodies do when they impinge mutually on one another.

[4. The numerical evaluation of the three causes.]

Thesis 10

Since, therefore, the sun reaches Prague almost four times higher in summer than in winter,14 it follows from this reason and the one mentioned earlier that on the shortest day there is not more than an eighth of the heat that descends from the sun to the elements on the longest day of summer.15

Thesis 11

But not even all of this eighth part of the heat that remains in winter is of benefit to us. For the sun, which is elevated only a little above our horizon in winter, has our dense atmosphere set more in opposition by its obliquity. Let us assume now that the surface of still air that refracts the solar ray is per- pendicularly one German mile from us. (It can hardly be higher, for is it not that same altitude of matter that produces the twilight and that refracts the rays of the stars [ ?]). In summer, therefore, a thickness of one and a ninth German miles is opposed to the solar ray, and in winter, three and a third [Ger- man miles]. Thus the sun's ray in winter is three times weaker on this account, and with these three reasons taken together, hardly a twenty-fourth part of the summer heat remains in winter.'6

[5. The heat capacity of the earth.] Thesis 12

Even though these three causes are indeed most evident on the actual days of the winter and summer solstices, still on the former the cold will not necessarily be the greatest of all, nor on the latter will the heat be the greatest of all. There enters in another cause which by its own right will make winter more intense from the beginning of February and summer hotter from the beginning of August, or thereabouts. For earth and water are dense bodies and cannot be heated in one moment, and after they have been heated around the month of June with the sun at its highest, they retain the heat that has been deeply impressed upon them (even if they remit some of it nightly from the surface) because of the density of their matter and the magnitude of their bodies; and thus they accumulate the heat of June from the past with that of July and August. The same thing must be said conversely about the cold of winter.

Thesis 13

Let the same judgment apply to the second hour of the day, which is warmer than the twelfth, even though the sun is already going down. For air ex- hibits in this instance the same characteristic that earth exhibited [in Thesis 12]. For air, being very thin, is changed more quickly than earth, but not altogether suddenly. At least the surface of the earth, if not the whole body, shares [in this characteristic].

Thesis 14

From the same principle it can be predicted that for the same reason September and October will be indeed warmer than March and February, even if the length of days will be the same for both.

B. THE MOON: [The physical function of the moon is to humidify. In addition to monthly moisture cycles, it also influences daily moisture cycles, as witnessed by the tides.]

Thesis 15

Another physical cause of predictions is the moon. For it has been proved by experience that all things uniformly moist swell with the waxing moon and subside with the waning moon. This one fact is the reason for most of the choices and predictions in domestic economy, agriculture, medicine, and shipping. The reason for this natural inclination has not yet been clearly recognized, according to physicists.

Thesis 16

Now there is a twofold power of the moon: one is monthly, about which I have already spoken, depending on the changeable appearance of the moon; one is semimonthly and for that matter even semidiurnal, which has the greatest force in medical crises and in the reciprocal tides of the sea, about which [I shall say] more below.


KEPLER ON ASTROLOGY

Thesis 17

On whatever days, then, the new moon is found on the calendar, humors insofar as they depend upon the moon will be diminished; on days of the full moon, they will be increased. But along with the days already cited, humors will also be moved strongly at the quarters. This is a simple and purely astrological prediction, but if it should be applied to specific fields, the astrologer would exceed the bounds of his own profession and would become a farmer, doctor, chemist, etc.

Thesis 18

But sometimes it behooves those men to be warned. For instance, I offer this [warning] to chemists: that the full moon appears unsuitable for the melting of metals because the air is too humid. Even so, a great choice of [favorable] aspects will appear for their work.

C. THE PLANETS: [The physical means by which the planets influence the earth is the light that comes down. Insofar as it is reflected light it humidifies (as with the moon), and insofar as it is radiated light it warms (as with the sun). Further, each type of light can exist in three degrees: excess, moderation, or deficiency. These six types differ from the four tactile sense contraries of Aristotle (hot, cold, wet, and dry) by the inclusion of the moderate term between the extremes, which is suggested by the example of geometry.]

Thesis 19

The third physical cause of predictions is the varied nature of the remaining planets, seen in the colors that they themselves give forth. And we shall be mistaken here if we distribute the four usual qualities to the planets. For old and dryness are not positive dispositions but ones [that arise when] deprived of light and related life. For cold and dryness are greatest where there is an absence of all light, all life, and thus all heat. Since, therefore, nothing descends to us from heaven but the light of the stars, certainly cold and dryness will not come down by themselves.

[1. The faculties of light.]

Thesis 20

We shall deduce both the diverse forces of the planets and their number in a manner different from, though not inconsistent with, Aristotle's [method of deducing] his four elements from combinations of the four qualities.'7 Every variation arises from contraries, and the principal variation [arises from] principal contraries. Wishing to philosophize more sub- limely and more generally beyond geometry, Aristotle assumed in his Metaphysics the principal contrary was that of the Same and the Different. It seems to me that diversity arises in created things nowhere else than from matter, or because of matter; and where

there is matter, there is geometry. Thus whereas Aristotle postulated a principal contrary without a middle between the Same and the Different, I find that in geometry that is philosophically examined, there is indeed a principal contrary, but with a middle; hence what was one term, Different, to Aristotle, let us divide into two terms, More and Less. Since, therefore, geometry will have offered a model for the creation of the whole world, it is quite appropriate that this geometric diversity will work for the adornment of the world, which depends on the diverse forces of the planets.

Thesis 21

Now, then, since these terms-the Same, the Dif- ferent, Equal, More, Less-signify nothing per se, we must think about the subjects themselves. Now the subjects, or natural qualities with which these propositions deal, are derived from the following. Our most discerning Creator made it his priority to establish a corporeal world. As he first conceived of creating, therefore, He conceived of matter, which we know from Moses to have been water, that is, wet, earthen, and tractable. This, then, is the one natural quality: namely, moisture. But the body of the world was not sufficient to the Creator unless something in some way similar to the Creator was made and endowed with life and movement. This, then, was the other quality: namely, life. Now because we are discussing the forces that the stars exert on bodies below, we ought to consider whether anything descends to us from the stars. Not matter or body itself, for that is in our possession before-hand. Not life itself originally, for all living things draw life from the movement of the soul which is within them. To be sure the stars do not generate life, but they help it. They serve, therefore, the function of an instrument. They provide us with two instrumental qualities to correspond with the number of natural faculties: 1) through the power of humidifying making possible the tractability of matter, and 2) through the power of heating making possible the fostering of life and movement. Both of these powers they possess and exercise through the benefit of light, which they have received and send down to us continuously. For the proper quality of light inasmuch as it is light is heating; but the proper quality of light insofar as it is reflected, is humidifying.

[2. The variety of possible combinations of faculties.]

Thesis 22

We therefore have two faculties, heating and humidifying, with a threefold division, if you will, excess, mean, and defect. Let us see how much variety may issue from this. First, there can be solitary faculties, such as heat in excess, mean, or defect,

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and humidity in excess, mean, or defect. Here are six differences. Then from a combination of both faculties there arise nine differences, which is clear from the table given below.

There are, then, fifteen differences in all. Let us now see which of these are selected and which are rejected in nature.

[3. The combinations selectively assigned to the sun, moon, and planets.]

Thesis 23

First it is reasonable that no excess or defect exists alone without compensation. Of the six solitary qualities, then, four are eliminated. Indeed the position of mean heat (we shall estimate the mean not by quantity but by its relationship to the world) has been assigned to the solar body, which uses purely its own light; the mean state of humidifying [is assigned to] the lunar body, which uses purely the borrowed light of the sun and stars.

Thesis 24

Now, then, excess may not be accumulated readily, nor may defect. For they are rather estranged from nature, nor may excesses be received unless they are tempered with defect. And so no planet has been made that received either an excess of both or a defect of both. Seven varieties remain, then, from the combinations. Further, two pairs of these combinations are reduced to the same thing. For there is the same proportion between excess of heat and mean of humidity as there is between mean of heat and defect of humidity; and there is the same proportion between defect of heat and mean of humidity as there is between mean of heat and excess of humidity, as the parallel lines in the figure illustrate. There is the same consideration regarding combined excesses and defects.

There are, then, five true variations, three simple, two-as already explained-in a way twofold, but really with two names, and one with three. And since there are also five planets in the world, three superior and two inferior, it is indeed appropriate even on this account alone (although other reasons may also be at hand) that they have been made in this number. Moreover, there could have been nothing more suitable than this distribution of combinations among them, which distribution I set in plain view in this chart :18

' Excess

be Sun . Mean

k Defect

JUPITER S mer S S

A cu U R TN rA

VE M y JUPITER

mer S S R cu U

A N r R MVE y N

JUPITER

Excess

a

Mean ' M Moon

Go

Defect )

[4. The physical cause for difference of degrees of faculties for individual planets is attributed to the influence of the color of the surface of the planet on the reflected and radiated light from the planet.]

Thesis 25

From this chart it follows that the five planets enjoy not only the borrowed light of the sun, but they add something of their own as well; and indeed other reasons also support this [assertion]. For if many physical bodies among us have innate light, what prevents other celestial spheres beyond the sun from having the same? Moreover, if planets were lacking their own light, it seems that they would have to change their appearance, like the moon.19 Finally, it is plausible that the brightness and twinkling are an argument for innate light, and cloudiness and inertia, [an argument] for reflected [light].

[4-a Reflected light]

Thesis 26

Now we must consider this point as well: what is it that can distinguish these forces of planets in excess, mean, and defect? Since we have deduced their light as borrowed from reflection, we must consider the varying kinds of reflection on the basis of the difference that exists on varying surfaces. I am not speaking now about that reflection that issues from a mirror and is reflected from any point of it to only one other point; but rather [I speak] about the reflection that we see from some wall, that is of uneven and rough surface, which reflects the light with which it is illuminated, tinged with the color that it [the wall] possesses, from any point of it onto the whole hemisphere. For the reflected light of the moon reaches us in the latter manner, not the former; otherwise we would not see horns on the moon, but always a small, round image of the sun. Consequently the geometric disposition of the surface causes nothing except perhaps the dark spots that we see on the moon.20

Thesis 27

Indeed the causes of one or another reflection (the cause of quality in the reflected ray) are the colors of the reflecting surface. Here I would like the chemists to hear what changes the colors in terrestrial bodies. The colors of the rainbow are, to be sure, divided into two classes: one has its source in obfuscation, or deprivation of light; the other, from refraction, or tinting. The source of each class is from the very light itself or, from a white glow analogous to light, which, occupying the middle circle of the rainbow, cuts it, as it were, in two.21 From one side it is diminished, and from the other it is refracted; finally on both sides it ends in black or darkness. In the first step of diminution it becomes yellow, in the


KEPLER ON ASTROLOGY

second, red, then dusky, and finally, black. The same thing appears in the clouds either when the sun has set or is about to rise;22 the same thing appears in the stars around the horizon; the same thing in solar eclipses, when our eyes, in which this delusion occurs, are suddenly deprived of the light of the sun. In the first step of reflection however, green is seen, later blue, then purple, and finally utter black or darkness.23 Since, then, this is the order of colors in the rainbow, it is appropriate that the same order follows also in reflection: that a white surface reflects a ray most strongly, then green and yellow, then blue and red, then purple and dusky, and surely most weakly, black.24

Thesis 28

Now black, when it is strongly illuminated, scatters a red ray. This [phenomenon] appears in mirrors of steel, when the white color of the face, mixed with the black of the mirror, presents a rather ruddy appearance. On this account someone said quite rightly that the star of Mars was endowed with a black surface, since its ray is very ruddy. Therefore light reflected from it is weakened, and therefore it does not humidify much, and there is a defect of humidity. By the same argument of color and humidity we shall assign to Saturn a white and rough surface, because it has a leaden color; to Jupiter a red or purple surface, because it appears reddish yellow; to Venus, yellow or white and a very smooth surface, since it is the fairest of all; to Mercury, blue or green, since it appears silvery, more bright by its twinkling or diluted brightness than from its color.25

[4-b Radiated Light] Thesis 29

The intrinsic light itself is varied through the surface of the body whence it has come, so that it gives now one color, now another, but it acquires the degrees of heat-producing power from the internal disposition of its own body. But still even the very surface gives evidence of the disposition of the body, so that its power to humidify depends in some way on its power to produce heat. And clearly if color can be propa- gated and transferred from one body to another by the intervention of light, it is credible that other qualities can also be [transferred]; as for heat, indeed, this [transfer] is most certain. Therefore as each planet displays power in its effect, it seems appropriate that there is an analogous disposition in the very body of the planet. If this holds true, it can lead us to construct wonderful theories. For example, I would say that in summer it is not healthy to live in the neigh- borhood of a wall strongly struck by the sun, because cement is made of lime, and since this [substance] has the power of corroding and consuming, it imbues the ray it reflects with this quality. Some trans-

parency seems in particular to be associated with intrinsic light. For if there is intrinsic light in anything, it does not in any case cling to the surface but has its roots driven into the inmost depths, as we see in gems. In order for it to shine through, there must be transparency. To be sure, however, many things become transparent by heat alone, and these remain in that disposition.

Thesis 30

Philosophers will forgive me as I draw conclusions from bodies that we investigate close at hand to heavenly bodies. For clearly philosophers themselves disclose no differences at all among those bodies. Why, as they probably think, should they transfer base and terrestrial differences with equanimity to heavenly bodies? But it is preferable to say something that falls into no palpable absurdity than to say nothing at all. And clearly I am not sure whether we ought not to call divine and heavenly rather that quality in the carbuncle gem that produces its little light, than that elementary quality of the sun's for heating. Thus I say that Saturn exceeds in humidity, is deficient in heat, and in the disposition of its body is like ice (which is itself very humid, since it is water, and deprived of all heat); hence, its white surface, and therefore the rather dense and not quite transparent internal disposition of its body. Astrol- ogers say that it is cold and dry, which comes to the same thing. But when it works to make summers rainy and winters snowy it deserves more to be called humid. We shall assign to Jupiter a body like a ruby, since it is transparent because of its great intrinsic light, and even and red because of its brightness and color. Mars will be likened to a glowing coal from which a latent inner fire shines through; for astrologers say, and experience bears witness, that it possesses a torrid and vehement power through its heat. We shall give amber to Venus with its uniform and yellow surface because of its exceptional yellow brightness, since it humidifies so much more than it heats, which property seems to require a rather soft body. Finally Mercury will be likened to a sap- phire or something similar, because it is suffused with transparency at the point of its rays and sends out more intrinsic than borrowed light, because it has the combination in which heat surpasses humidity.

[5. The applications of planetary properties to the making of predictions.]

Thesis 31

Thus by reason of borrowed light, or humidity, the emersions of planets, or their occultations and oppositions, can be considered. Saturn, being in opposition to the sun on May 11th and in conjunction with it on November 18th, will exercise its humidifying faculty most strongly on both dates

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because it will turn towards us a face fully illuminated by the sun. This faculty will be at a minimum on February 11th and August 9th, when Saturn is in either quadrature. Jupiter will humidify most strongly at opposition on April 8th and at conjunction on October 26th and will be the reverse [weak] at quadrature on January 8th and July 6th. Likewise for Mars (although it has very little [power to humidify]), which will be in opposition to the sun on March 5th and minimal at quadrature on June 9th, and successively in the intervening and following periods. The conduct of Venus is different, as is that of Mercury. For when Venus is at superior conjunction with the sun on May 15th, it will humidify most, but before and after, [it will humidify] successively less; and in another year hence it will humidify least at inferior conjunction with the sun. In this way Mercury will humidify little on January 4th, April 30th, August 29th, and December 19th. For at inferior conjunction with the sun it turns upward its whole face illuminated by the sun. But it humidifies most on March 9th, June 27th, and October 19th, when it is at superior conjunction with the sun and turns its illuminated face downward.

Thesis 32

With regard to light and intrinsic heat-giving power, there is some doubt whether the high or low planets are stronger. The astrologers prefer high, the physicists, low. Let us set up a compromise here, so that the greater the angle at which they are seen (that is, low), so much more do they heat because of this very angle of vision. But the power that is increased by height has another cause.26

Thesis 33

In regard to the powers of heating and humidifying we must consider in which sign the planets are turning. For both the planets and the moon exercise the greatest influence in Cancer because they are longest above the earth and for other reasons mentioned at the beginning when I was speaking about the sun.27 Thus, also when they are in the north, they are more powerful. Hence full moons are more humid at winter solstices than at summer ones. Thus in northern latitudes for this year and some years to come the already described powers of Saturn and Jupiter, and even Mars at the end of the year, will be weak, because they will be moving in low signs. But in southern latitudes they will be so much the stronger.

Thesis 34

Since we observe in motion that whatever is slowest is most powerful, hence we deduce reasons why stationary planets and those in apogee are so powerful. The station of Mercury is the most efficacious of all, for Mercury, being swiftest at other times, loses the

most motion. The station of Saturn is least efficacious because it has little motion to lose in its station. In- deed the station of Mercury stirs up winds in general, and where there are rains and snows it stirs up copious vapors in kind. We shall expect these [storms], therefore, around January 17th, April 20th, May 12th, August 15th, September 6th, and Decem- ber 9th and 31st. But still the uncertain motion of Mercury does not allow us to determine the day beforehand with the greatest certainty.

D. A SUMMARY OF THE PHYSICAL CAUSES [The role of light as the primary physical cause is reviewed.]

Thesis 35

Those causes of future events that I have explained up to this point, even though they do indeed possess much of the divine, neverthless all resemble the nature of matter more nearly than those which now will follow. For their method of operating consists in a certain flowing out of light continued as far as these sublunary bodies; although this flowing out is without matter and time, neverthless it is not without quantita- tive dimensions. For it is made in a straight line; it is attenuated with distance from a star; it increases or decreases with the face of the shining planet; it is impeded by the interference of an opaque body; and, on the other hand, given the visible presence of the star, it flows continuously. This [method of operating] takes place not only in one and the same star, but it also applies to a comparison of different stars; so that since the sun and moon are largest in size, these powers are most visible on them. In others, whose diameter is small in comparison with that of the sun and moon, the powers are rather feeble and even hardly, if at all, perceptible. The mob of astrologers nearly neglects the variations of these effects according to the methods specified.

SECTION TWO: ON GEOMETRICAL CAUSES [There are three major sources of geometrical causes: aspects, cycles, and planetary harmonics. The animate faculty is introduced and is described as the primary receptor for these geometrical causes, which do not require the intermediary of light. The attempts of astrologers to use the signs of the zodiac to predict events is decried; the attempts of agriculturists to use astronomical events to predict weather is applauded.]

Thesis 36

There follows, then, another cause, which pertains equally to all planets, nobler by far than that [mentioned] earlier, and one possessing far more wonder. For it is not a material cause but rather a formal one, and the form which it has is not simple form, but form in animate faculty, in intellect, in geometric cognition. For [this cause] does not draw its power along straight lines from single stars, but it takes into account the rays of pairs of stars as they meet


KEPLER ON ASTROLOGY

on earth and form a geometric or non-geometric angle. And this [cause] is not extinguished along with the very face of the silent moon, when no rays descend to earth, but the descending ray is then imagined. It is not impeded when the earth is placed between us and the stars; but it makes the stars hiding below [the horizon] also efficacious above. Finally it is almost instantaneous, and when the angle is commuted from a geometric to a non-geometric and non-harmonic one,28 it is inactive at once, or a little later, no matter how much the lights of the stars are increasing. Since these powers have been confirmed most de- cidedly by experience, they have supplied me with the following theories.

Thesis 37

Since God, the Creator of this corporeal world, has chosen to adorn it with corporeal form, which is quantity, it is appropriate that the locations themselves, the spaces themselves, and the masses of bodies have been selected in that mutually proportionate way that has arisen from the regular kinds of solid figures, which I have demonstrated in my Cosmic Mystery: 29

i.e., that in truth the motions of bodies, which con- stitute the life of the world, are all perfectly in tune, or act strongly in unison, when they take their proportion from the regular planes [of the solid figures]. For as the plane is the representation of a solid, so the motion is the representation of a body. Just as in fact in geometry it is impossible that there should be more than five regular solids, and similarly the harmonics that arise from a comparison of the regular plane surfaces cannot be more than eight, as I shall point out, God willing, at another time in my book On Harmonics. S

A. Aspects [Eight geometrical configurations are listed the five traditional aspects plus three new ones.]

Thesis 38

Therefore since there are eight formative ratios of motions, there is some action (or, as it were, motion) of heaven on the earth when it meets an intermediating ray of a star and they then come together on earth to form angles; thus the eight harmonic ratios will be expressed in the dimension of these angles. Now the ancients did not acknowledge more than five [of these angles] (commonly called Aspects): Conjunc- tion, Opposition, Quadrature, Trine, and Sextile. But reason soon led me to add three more: quintile, biquintile, and sesquiquadrature,31 which many experiences have since confirmed.

[1. The Animate Faculty is discussed as the receptor of the geometric causes. It is sensitive to aspects.]

Thesis 39

The reason why the influence of pairs of planets is so strongly enhanced at the very articulations of their

aspects [i.e., on the earth] I can attribute to no other cause than to an animate faculty, which, on the one hand, is capable of the geometric plan (which shapes the aspect), and, on the other hand, is in control of that body on which the influence is directed. For this [influence] does not come about because rays join together to form any angle. For pairs of rays form some kind of angle on the day before and the day after the aspects, and forever; but the influence is manifested finally when the angle possesses a harmonic ratio, or schema (Ptolemy says schematism). But there is no efficient power per se in ratios or schemata. The same thing obviously happens here that usually happens in the locomotion of animals. If one should say that the objects of vision were able to move the animal as they enter the eye, and that therefore there was no need of an animate faculty in the animal itself that was moved, one would be philosophizing strangely.

Thesis 40

Now this faculty, which adds force to aspects, is not located in the stars themselves. For these aspects we are discussing touch upon the earth and are a pure condition flowing not from the formal motion of the stars, but from the accidental arrangement of pairs of stars with the earth. In the same way, then, that the spirit moving the body is located not in the object, but in the place where the idea of the object is dis- played, just so is it necessary for this force, which makes the aspects powerful, to be located within that great globe earth, as it is in all the sublunary bodies. To be sure, every animate faculty is the image of God the Geometer in creation, and He is inspired to His task by this celestial geometry of aspects or harmony.

Thesis 41

To thoughtless persons this form of philosophy will seem new, which it is not, except insofar as I make a bit more general the ancient philosophic tenets. For, first of all, as far as the earth is concerned, no one will deny that the form of the whole earth, insofar as it is an entity, is nobler than the form that is recognized in any lump of earth. The works of the earth itself show that its form issues from the species of animate faculties; these works are the generation of metals, the conservation of terrestrial heat, and the exuding of vapors for the generating of rivers, rains, and other meteorological conditions. These [mani- festations] show that its form is not only preservative, as in stones, but altogether vegetative.

Thesis 42

Still it is not necessary on this account for the earth to increase in size or to be moved in location. For its spirit is not human, nor is it animal, nor plant,

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but it is of a peculiar species, which takes its definition from its function, just as other species of animate faculties do as well. And the same reason that com- pelled the ancients to assign a third species of soul to plants compels us to assign this fourth [species of soul] to earth.82

[2. The animate faculty is explained by analogy with bo- tanical genetics and naive appreciation of music.]

Thesis 43

But neither is it absurd that animate faculties, which do not have the advantage of discourse, are apprecia- tive of geometry and are moved by it as if by a certain object. Examples are easily found. The plastic faculty of a tree does not reason, and yet it carries out the commands of the Creator to the utmost, in the arrangement of its leaves for the benefit of the fruit and for a certain end. Yes, and even all the seeds retain that beauty which resides in numbers. Most kinds of plants enjoy five-sidedness; this five-sidedness is not necessarily transferred principally from the tree to the apple, in which transformation the preservation of five-sidedness is impossible; but [it is transferred] by communication with the plastic faculty, which possesses the inborn beauty of five-sidedness.

But the explanation up to now has been rather humble and less a cause for wonder, because the faculty resides within itself, and it propagates the five-sidedness that it possesses. I shall give a more suitable example. A peasant does not reason what geometric ratio one voice bears to another voice. And yet that external harmony of chords flows through the ears of the rustic into his mind and cheers the man. [And he is cheered] surely not by a moderation of the blending of voices, nor by the soft caressing of his ears (for often the ears ache from a violent sound and nevertheless they delight in the harmony) nor for any other reason that could have been discovered up to now; but [he is cheered] for this reason only, which I shall demonstrate in my Harmonics: because a certain geometric ratio produces beauty in the harmonies. [This geometric ratio] belongs to all the rest of the world and especially to powers that certain ancients called harmonies. Therefore, having advanced by these examples as if by certain steps, let us be bold to ascend even to this height: that we believe that there is in the earth a vegetative animate power, and in the animate power a certain sense of geometry that is formal and self-sufficient, because that power is of the species of animate faculties that- although it always inclines towards its own function- is nevertheless more stimulated when this [function] is refreshed as if with some nourishment of aspects. In the same way that the ear is stimulated by harmony to listen carefully and thus to hear much more, (seeking pleasure, which is the goal of feeling), so the earth

is stimulated through the geometric concourse of vegetating rays (which we said warmed and humidified) so that it applies itself so much more diligently to its function of vegetation and exudes a copious supply of vapors.

[3. The characteristics of individual planets influence the effect of aspects.]

Thesis 44

Even though the diverse natures of planets explained above vary the effect of aspects considerably, as at times the earth is affected by a geometric mingling of the opposites Saturn and Mars, and at other times of the similar planets Jupiter and Venus, in almost the same way that we observe purgatives effecting a movement of the humors in man's intestines, but especially rhubarb for the bile. (For is not a faculty that is capable of geometry also capable of color and other qualities in its rays?) But the strongest variation nevertheless is from the actual disposition of bodies, especially the earth, which is different in different places and at different times. For when in springtime, for example, humors abound in the northern part of the earth on account of the approach of the sun, about which we spoke above, then sometimes a very light aspect of any planets whatsoever, arouses that faculty of the earth to be moved and to exude some supply of vapors for the generating of heavy showers. At another time or place the strongest aspect by far may stimulate the earth, but because of a defect of matter, it elicits very little [response]. B. CYCLES [The second geometrical cause is the various cycles that exist both in man for short periods and in the earth for long periods. The question of the effect of eclipses is raised.]

Thesis 45

At this point we ought to understand another additional cause, the ignorance of which strongly disturbs the predictions of astrologers, since it is not yet recognized. For just as there are in people certain periods of humors that cause them to change their moods repeatedly without any evident cause, so that sometimes they are merry without music, and again no pleasure can turn them from their sad thoughts. Clearly in the same way I perceive that beyond aspects there are other causes, stronger and more lasting, which may bring it about that some whole year- and no aspect lasts so long-may be kept in humidity and hence in extreme cold. [In such a year] you may see weakest aspects as many times as they fall, exciting the greatest number of rains and winds; such a year was 1601. In another year, however, there is such dryness that on days of aspects nothing can be seen but little clouds, or mist, in place of vapors; such a year was 1599.


KEPLER ON ASTROLOGY

Thesis 46

I leave it for consideration whether this very strik- ing diversity comes from eclipses of the sun and moon (which must also be classified among aspects: namely, among conjunctions and oppositions). Let it be established, nevertheless, that the animate faculty of the earth, about which I have said so much, is thrown into vehement consternation by the sudden loss of light and takes up, as it were, a certain mood, which lasts for a long time; Theophrastus, who is not always full of fables, also seems to have sensed this [phenomenon]. For unless you either admit this [physical] reason, [that there are prolonged effects of eclipses], or, casting aside all physical reasons ascribe this ordinary work of nature to the extra- ordinary providence of God, you will not be able to explain why eclipses are so ominous.

Thesis 47

It is rather fitting, however, that here the same thing happens to the earth that happens to living animals, excepting their mortality, so that from a certain internal disposition, it has cycles of humors, and, as it were, diseases. If there are such things, laws and cycles of humors ought to be investigated from the collected observations of many years, and so far this observation has not been made. Caesius attributed some significance to the nineteen-year cycle of the moon, and his opinion is worthy of some credence. For both the highest tides of the sea are said by sailors to return after nineteen years around the same days of the year, and the moon, marked by humors, seems suitable for this task because it deals with excess and defect of humors.

C. HARMONIC MOTIONS OF THE PLANETS [The third geometric cause is the ratio of the motions (speeds) of pairs of planets. Not much is known of these harmonies, however.]

Thesis 48

But a third cause presents itself as very likely: the many sublunary movements of nature which I have said sometimes occur outside of aspects, are aroused by the harmonic motion of the planets. For if the proportionate angle of rays brings this about, why not also the proportionate motions of pairs of stars, as often as they are directed towards a harmony, so that one passes through an equal space more quickly and another more slowly in harmonic proportion. Now these ratios are variable, and they do not occur frequently, for the same planet is sometimes swifter and sometimes slower. Nevertheless this cause has not yet been confirmed by experience, nor has a method yet been constructed by which harmonies of this kind may be investigated.

D. OTHER CONJECTURED CAUSES [The futile causes offered by astrologers are contrasted with the worthwhile causes offered by farmers.]

Thesis 49

Astrologers seek a nonsensical reason for this general disposition of the years from the entries of the sun into Aries, for the [disposition of] the four seasons from the cardinal figures, and for the [disposition of] the months from the figures of lunations; as though the weather were some abiding object, like a person, whose birth we can reasonably examine, and not rather part of the motions of the heavens, or as though the earth could be restored to a new summer in one moment. Indeed the earth is changed by aspects of the vernal figure, if it has any, but only on that day; on preceding and succeeding days [it is changed] by other aspects depending upon which one appears on any particular day. But nothing is more intolerable in this almost unique concern of certain astrologers than that they distribute with a certain infantile credulity twelve houses among seven planets beyond every sound and philosophical reason; they invent tyrannies and momentary vicissitudes of empires, as if in some assembly of people. From this [concern] every magical and astrological superstition has arisen. We shall grant in some places that the appearance of truth results from this distribution [of houses], as in Saturn, to which wintry signs are given, but this [attribute] has other causes; moreover in other planets, like Jupiter, falsehood is produced. The astrologer Stoeffler, however, has some time ago indirectly refuted this trifling side of astrology with physical reasons (thus no testimony need be sought from the enemy [of astrology, Pico] della Mirandola); indeed experience daily refutes it, since after so many centuries astrologers have hardly ever known the exact time of equinox, as Tycho Brahe pointed out.83 Let them select some cardinal figures of past years and let them compare them with [observed] results; I shall point out to them that they were wrong in the time, and that even the true figures, examined by this false method, indicated a contradiction to the [observed] conditions of the following year. In the coming year the sun enters Aries on March 20th at sunset as Jupiter rises in Libra; the astrologers will think that Gemini will be about to rise, according to the Prussian tables. Nevertheless, no general significance can be deduced from this. For Jupiter indeed will exert its forces on the 8th of April, when in opposition to the sun. But on May 10th and 11th Saturn will succeed it, because it will be opposed to the sun on that day.

Thesis 50

But here I do not reject the observations of the very ancient authors Hesiod, Aratus, Virgil, and

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Pliny, and the modern observations of farmers, who from the annual risings of stars and from the phases of the moon, make a judgment about future weather conditions at the time when they observe these phenomena (or not much beforehand). For they observe these things not as a magic figure in the heavens nor as a cause of a future disposition (for in other years they take another prognostic), but as a sign of a general terrestrial disposition now present and continuing for a little while, but whose periods and laws I con- tend are not known at another time.

Thesis 51

Still it has been observed that there is a brief cycle to this succession of universal qualities. For even peasants (who understand this most shrewdly) expect a rather harsh winter when they have seen a torrid summer. And if some period of winter has remained unnaturally warm, they expect the last part to be so much the colder. Thus, at a time when winter has rushed in violently and rather precipitously, spring will be late in turn, given the agreement of the many aspects that occur at that time of year.

SECTION THREE: ON PREDICTIONS FOR 1602

[Specific predictions are made for the weather for each month in the year 1602. Further there are general com- mentaries on predictions concerning eclipses, crops, illness, political and military matters, and earthquakes. The section concludes with a discussion of four major aspects of special significance in the year 1602.]

A. THE WEATHER FOR THE YEAR 1602

Thesis 52

[January] I have recounted the strongest grounds for astro-

logical predictions; I shall use the remainder as far as possible, for the predictions themselves. First in the months of December, January, and February the sextile of Saturn and Mars will last unusually long, for it happens that Mars will become stationary at that time, and Saturn is characteristically slow. There will be a vehement commotion and a very definite excess in the atmospheric conditions. But it is not easy to say how the excess will be manifested. For in order to know this we would need to speculate on what the general disposition of the earth will be, which I think we are not capable of comprehending by any conjectures up to this time; and this disposition [of the earth] is stronger than the change in effect of the planets themselves through their distinctive forces. If that had been the only aspect [sextile of Saturn and Mars], I would have predicted extreme cold from the snowy exhalations. But now because of the coming together of many aspects, I think that there will be such a commotion (particularly because Mars is approaching its station) that the air will clearly be

warmed by tepid vapors sifted out from the bowels of the earth, and the snows will be nearly melted, and journeys will be greatly obstructed. On January fourth the conjunction of the sun and Mercury will bring snow or winds according to the general disposition of the earth. Around the tenth or eleventh there will be six very strong aspects [bringing] pure warmth and rains mixed with scattered snows. At the end nothing can be predicted from old aspects, but from the new ones we predict that the quintile of Jupiter and Venus will make the twenty-first breezy and warm, as far as winter allows. On the twenty-fourth the quintile of Saturn and the sun will bring cold, with snowy or rainy weather. On the twenty-eighth the sesquiquadrature of Mars and the sun will bring harsh weather, with biting and harsh winds, and snow for the time following. Then let those who have a mind to investigate new aspects observe these days.

Thesis 53

[February]

February springs forth with old and new aspects. In the beginning the conjunction of Venus and Mer- cury will introduce disturbances into the atmospheric conditions. For they also have the contrary nature of Saturn and Mars, as you have seen above. But I say this from experience, which testifies emphatically to their turbulent configuration. Perhaps it may also be on this account: because their paths are nearly equal, they are parted slowly and appear somewhat ponderous. There can certainly be thunderstorms as well. From the eleventh to the twenty-third of February there will clearly be no calm. Thus either it will snow very heavily, if the cold returns on the eleventh at the quadrature of the sun and Saturn, or it will rain very heavily, if the warmth lasts that long, which I rather believe it will.

Thesis 54

[March]

February twenty-first had six planetary aspects (the moon, being too swift, has hardly any bearing on aspects). March encounters twenty [aspects]. So the weather will be more turbulent than it was up to now, since this is also its nature at other times. The first part of the month will be thunderous and although the latitude of Mars detracts quite a bit from its effect, still the frequency of the aspects adds strength to it in turn. Thus I predict the unusual warmth up to this point will change to wintry cold from March thirteenth on; after that there will be continuous cold winds and snows mixed with rains.

Thesis 55

[April and May] I expect April to be normal with a warm beginning

on account of the biquintile on Mars and the sun, with


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rain two days preceding and following the full moon, for all the planets will be in alignment. There will be rains from the thirteenth to the sixteenth. After that, heat and around the twenty-fourth such an excess that it will erupt in thunderstorms on account of the triangle of the sun and Mars. At the end there will be showers again.

At the beginning of May horrible weather with thunderstorms will return at the conjunction of Venus and Mercury unless a different latitude enervates its power; and this is not certain, nor is the day definite on account of a faulty calculation up to now. On the tenth, eleventh, and twelfth there will be cold rains and on the mountains, either snow or not very health- ful air. But if the sky is clear, there is the possibility of frost to be feared. For beyond the old aspects, the quintile of Saturn and Mars is approaching from the new ones. A very beautiful pleasantness follows with humidity. At the end there will be thunderstorms and showers.

Thesis 56

[June] Since the universal cause of the disposition of the

years is not known, I must write about the summer as if the year, or the earth, will be in the same condition as this year. And since we are in such a state of ignorance regarding the causes, I think that astrological conjectures regarding any particular period ought to be forgiven if they are wrong. For we must not call superfluous those conjectures that are occu- pied with matters of the greatest usefulness beyond question, if ever those matters that now lie hidden are to be brought completely to light. And so I declare that the beginning of June will be hot and serene; after the full moon there will be dangerous disturbances, floods, and frequent flashes of lightning. If the general disposition of the earth inclines towards dryness, there is no danger. If, on the other hand, it inclines towards humidity, there will not be flashes of lightning, but continuous and cold rains. The last of the middle has been divided as if in continuous sta- tions among their aspects. There will be disturbances. I should think it likely that the coming month would be quite cold, because of the great amount of humidity, if this entire year of 1601 had not been so. If the year as a whole should be inclined towards dryness, the degree of dryness will be even greater in this month.

Thesis 57

[July]

July has the same appraisal, with the same ambigu- ity, for it has 18 aspects. Now seeing that there are around 150 aspects yearly, for the most part these will be accumulated in the summer half for this year. The first, second, fifth and sixth days will be

moderate, and windy with showers. The eighth day will be windy and cold, and the ninth and eleventh, blustery. But the twelfth, thirteenth, and the fourteenth will be troublesome at the conjunction of Venus and Mercury, which is repeated for the fourth time in this year, and there will be heavy storms. The eighteenth, nineteenth, and twenty-first days will be mixed, with thunderstorms and showers about to break. From this point, it will be fair and very hot, for Jupiter and Mars will be in conjunction at the beginning of August.

Thesis 58

[August]

Finally in August there will be some calm and heat. On the fifth and ninth days there will be rains [and] around the fifteenth, cold rains with thunderstorms. Heat will follow these storms, and on the nineteenth, there will be a strong disturbance.

Thesis 59

[September]

September will be normal at the beginning. The eleventh day will be cloudy with rains; the fifteenth and seventeenth will be humid. But the twentieth day is rather disturbed by the conjunction of Saturn and Mars. If a moderate heat has preceded, now there will be terrible storms. But if the year has been generally humid, there will be heavy rains with cold on these days. In general it will be mostly cloudy; the twenty-seventh day will also stir up the clouds. The other days will be normal.

Thesis 60

[October]

There will be cold rains on the fifth of October. The rest of this month will display the same conditions as those of the preceding month of September. For, as it has often been said, it is of great importance to find out what the disposition of the Earth is for any particular month. The third, ninth, and twenty- seventh days will have storms. The twenty-eighth and twenty-ninth days will have roaring winds and rains, but I think that heat will prevail, even though the nature of certain winds from their own regions [may be] very cold.

Thesis 61

[November]

In November there will be the usual number of hailstorms, and the fifth will be disturbed with biting winds. The fifteenth is changeable and warm for this time of year because of the sextile of Jupiter and Venus. The eighteenth will have rains, and if it is clear, there will be the first frost. But I cannot believe that it will be winter yet. For at the end of the month Jupiter will be in alignment with Mars and

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Venus, making the days still warm and cloudy with winds, which will cause cold weather occasionally in some places.

Thesis 62

[December] I predict that the third of December will be the

beginning of winter, a snowy and cloudy day, but still not cold. From this time there will be fair weather, with calming aspects, and throughout this calm, moderate cold. There will be snow on the fifteenth. The cold will be unstable on the nineteenth, and there will be substantial winds and clouds. The Christmas days will have the sextile of Saturn and Mars, which will increase the cold; after that, the sextile of Venus and Mercury will cause snow.

B. ON ECLIPSES

Thesis 63

I have passed over the alignments of the moon with the planets for the reason stated above. Nevertheless, I must not omit, also for the reasons stated above, the meeting of the moon and sun causing an eclipse [solar eclipse] before the beginning of the coming year, and also the two ecliptic full moons [lunar eclipses] on opposite sides of the heavens. [Of the latter] one will be in 17?48' in Gemini, the beginning of which, according to an observation carried out here in Prague, will be on the ninth of December at 5:07 P.M. and end at 8:33 P.M., coming as close as possible to the calculations of Tycho; the other will take place on the fourth of June in the year 1602 in 13?32' of Sagittarius, whose beginning will be at 4:52 P.M. on earth. It will begin in complete darkness, and it will end at 9:06 P.M.

Indeed I observed the beginning of the eclipse of the sun on the twenty-fourth of December at 1: 17, and the middle at 2: 42 in 2?53' of Capricorn. It was ten inches from the north. The sun set before the end. This eclipse is quite notable, and if it is in the power of eclipses to effect changes, this one will indeed have remarkable effects, especially in the north, where it has appeared most conspicuously. But still I feel that it is uncertain how it will affect the following year. For the instructions of Ptolemy are dubious, and they do not conform to nature.

In the year 1598 there was quite a large eclipse in Pisces. When the sun came in the month of Septem- ber to the opposite constellation of Virgo, there were copious rains. In the year 1600 there was an eclipse in Cancer. When the sun returns to Gemini and Cancer, the weather will be humid both at that sea- son and for the entire summer following. Let the experts in these matters consider whether the reasoning proceeds correctly: if I neglect the influence of this eclipse on December of the year 1602 and this winter,

I shall predict the signs of a great cold. But if eclipses obtain their force from the configuration of the heavens (for, granting the influence of the eclipse, one must also grant the influence of the sign), indeed all three eclipses occur in aspects of Jupiter and Mars, and on this account they would signify the adverse effects of Jupiter: for example, warmth and disturbed humors, and hence disadvantageous birth.

Thesis 64

Another eclipse of the moon will be seen on the twenty-eighth day of November in the west, which, according to the calculations of Tycho, will begin here in Prague almost with the rising of the sun and the setting of the moon. And because this [eclipse] falls within our horizon, as does also the eclipse of the sun which we in the West will see on the nineteenth of June, of what use is it to arouse fearful cries about them? People are certainly ridiculous when they consider so many eclipses in one year to be ominous; as if they would not occur four and five times a year if only we could see the whole globe of the earth. But men fall into error in this matter, because recently Origan published his Ephemerides, in which he com- puted many events occurring over the whole earth; this is something that others had not undertaken before him. If it had not been for him there never would have arisen these fearful voices shouting about the eclipses within our horizon, for these people, thunderstruck, look into the sky for something new when the only thing that is new is Origan's method.

C. ON CROPS

Thesis 65

Predictions about crops are rather uncertain. As far as natural influences are concerned (we all know about the providence of God) crops depend partly upon fortuitous causes, and partly upon that general disposition of the years discussed above; the former of which is incapable of being foretold by its very nature and the latter of which is being investigated in these pages. The stuff of empty dreams are those divisions assigned by astrologers to grain, wine, oil, corn, etc. according to the dispositions of the cardinal configuration of Jupiter. Do you want to know why wine has not turned out well this year? Because the year has been cold and humid. Whoever has made this observation has understood the effect from this cause alone. Why was the remaining crop lush in some places and thin in others? Because, as I have argued above, some parts of the earth were humid because of some internal, and up to now hidden, disposition of the earth, and enough of the summer was fair. But in other places there was dryness, which was harmful to fruits, and also an earthquake followed.

Sometimes, to be sure, the year is going well, but


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suddenly and in one day either frost or hailstorms do damage to the mountains, or flooding does damage to the lowlands when the waters spill over into another district wherever they are carried by the wind. Hence it is of the utmost importance to investigate the nature of winds, whose attacks on these regions of ours are most inconstant. And so it is very foolish to seek other causes of these events in the cardinal configurations, when we see them revealed before our eyes. But lest I seem to be an upstart in overthrowing this art, I call upon the authority of Cardanus and Tycho.

Thesis 66

I shall consider one cause, storms, since there is not yet general agreement about other causes. In southern regions an early spring provokes the trees to burst into bloom ahead of time, and these still tender blossoms will be damaged by the advent of an inclement March. In our climate, at that time, nothing is blossoming because of the usual cold and the north wind. Spring will bring fruits at the right time, but the tenth, eleventh, and twelfth of May are in danger, as stated above. June will threaten the flowering vine, for both this month and July that follows will see destruction here and there either from too much humidity or from hail. August, September, and October seem favorable for whatever grapes remain on the vine, and for grain as well. Nevertheless, the twentieth of September holds danger for that period.

D. ON ILLNESS

Thesis 67

As far as illnesses are concerned, doctors know this truth universally, that when the air is disturbed, our bodies are disturbed. Thus, since an inclement winter is forecast, there will be many people ill, especially in the beginning of March and May. But if the summer appears turbulent, the following autumn will be quite bad, because of the conjunction of Saturn and Mars, and there will be many autumnal illnesses, and plague in some places brought in by the wind, especially if one considers the eclipses, about which I have spoken. I have noted some days that are troubled in general by close aspects; these will incite illnesses in likely subjects, and those already ill will become worse.

But if someone collapses now, or if harmful humors are flowing in the body at this time, then clearly one should not neglect, as I have done up to now, the configurations of the moon with the planets [and] especially with the sun. For in a very particular way they order and move the humors, (to which that great chaos of humors, the ocean, testifies), and I would affirm that configurations ought to be considered in the advantageous practicing of medicine. Doctors, if they can, will leave an invalid alone who

is terribly weakened, when the moon is turning in a strong aspect. For any aspect whatever is a purga- tion of nature in its own right. But if strong purga- tions are needed, one must select strong configurations. Furthermore, the whole matter of crises clearly depends upon the revolution of the moon and upon its configuration with the planets, and it will be sought elsewhere in vain.

E. ON POLITICAL AND MILITARY MATTERS

Thesis 68

Astrology clearly has some say in political and military matters, given those statements I have set forth above in the passage on fundamentals regarding the agreement of human dispositions with celestial configurations. For every kind of human disposition that has been roused to lively activity naturally by its own motivation will be moved to vigorous activities in strong aspects, especially if the aspect has a similarity of origin with the particular individual under consideration. This "sympathy" arises not from the temperament of the body, as though the sky should set it into motion through the air, and this should act on the temperament of the body, and this should act on the mind; but, on the contrary, the mind of its own accord shares feeling with the sky, because it [the mind] possesses cognition with light and harmony; yet later it alters the body as well. Further- more, since a person is a social animal, dispositions are particularly oriented to a public undertaking when those rays of planets are oriented geometrically in the heavens. But this task may be undertaken more accurately if there are ready at hand the horoscopes of those who (if I may use a Tychonian phrase) govern public destiny.

Thesis 69

It is very foolish, however, to look here for those particular matters, the number and quality of which the curious seek in the almanacs. For what I have said about meteorology should hold here as well: nothing can be sought from astrology than a certain driving force of dispositions; whatever will happen in human affairs is in the power of people's free will, which is the image of God and not the offspring of nature and in the power of other causes. Therefore, as to whether there will be peace or war in any particular region, let those judge who are skilled in political affairs, for they have no less skill for predicting than does astrology. Certainly political affairs have their own character as much as the flowing motion of the heavens.

But if there is war in any region, the dispositions of soldiers and leaders will be disposed towards strata- gems, battles, attacks, and other movements especially on the following days: the twelfth of January;

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the fifth, fourteenth, and twenty-fourth of February; the fifth and fourteenth of March, the fifth and twenty- fifth of April; and fourth, twelfth and thirty-first of May; the ninth and twenty-first of August; the twentieth and twenty-seventh of September; the third of October; the fifth, eighteenth, and thirtieth of November; and the twenty-fifth of December. And experience confirms this view.

F. ON EARTHQUAKES

Thesis 70

Earthquakes, whether rather notable or completely unheard of, do not seem to be indicated by the heavens since Saturn and Jupiter will not be in alignment this year; however, the sky is only one very general cause and sign of great earthquakes.

For more often specific and natural events occur in sublunary affairs which it is not the province of astrology to predict. Consider, for example, the earthquake that occurred in September of last year, 1601, which shook most remarkably the entire district of the Rhine and regions nearby. They say that its force was felt even in Lombardy. These [occurrences] I predict, not from astrology, since an earthquake is not of the stars, but from observation of the earth and all the seasons, from which it is clear that the movements of troops and human dispositions are [also] wont to follow.

G. ON FOUR MAJOR ASPECTS OF SPECIAL SIGNIFICANCE IN 1602

Thesis 71

Four astrological events of particular importance may be added here: the eclipse of the sun in 3? Capri- corn; the sextile of Saturn and the stationary Mars, which lasts throughout almost all of January and February and returns in the month of June; the conjunction of Jupiter and Mars at the end of July; and the conjunction of Saturn and Mars in the month of September. First, experience shows that under these two conjunctions souls are generally stunned and frightened, or aroused in the expectation of revolts, and this fact is very significant for a multitude of people congregated in one place either for some undertaking, or for destruction, as military experience testifies. The defeat at Eger34 in the year [15]96 occurred at the opposition of Jupiter and Mars; likewise, [the massacre] at the marriage in Paris35 in the year 1572 occurred at the conjunction of Saturn and Mars. I would think that it is not entirely useless for leaders and rulers of people to be taken up with such considerations; for in order to rule the multitude one must have great skill and an awareness of those forces that affect human dispositions in a group. Thus if it is preferable for peace and quiet to prevail, and

sedition is feared, let meetings not be held in August and September, or let them be broken up, or better yet, let the causes exasperating people's dispositions be taken quickly away, or by the introduction of some new deterrent, let their minds be changed. If some bold venture must be undertaken and must be accom- plished by exciting terror, let August be chosen. If the mind must be hardened for some labor, let it be in September.

But if in these months the enemy should dare some boldness, take up suitable remedies to guard against consternation in the minds of the people. For these remedies are always in our power, however things may happen, and nothing is absolutely predestined. Cer- tainly the past year has testified to this with a very clear example.

Thesis 72

Then, a great safeguard for the army lies in their loyalty to and high regard for their commander; for every victory depends on a driving force of the spirit. If, on the other hand, the leaders should be held in contempt because of an agitation of their horoscopes, danger through their own fantasies would afflict the army and the fortune of war. Thus when the conjunction of Saturn and Mars falls in Poland at sunrise, and the eclipse of the sun is strongest in Moscow and Poland, and if there is already war there, I think that defeat is predicted by that aspect. If someone should accommodate this agitation of the horoscope to his own strengths, he himself may inflict defeat; but if a strong peace grows firm in the meantime, clearly there is no danger from the heavens alone.

Thesis 73

In the third place, the conjunction already mentioned affects our country as well; since it is very spacious, not only the sky, but sublunary causes affect certain sections. For although the sun shines upon and warms the whole world, yet it does not produce olive trees everywhere, except where they have been planted. But yet because of an earthquake and horoscopes, and eclipses of the sun, which affect the sun's position for France and Spain, we shall await some event touching Sweden, Switzerland, Lombardy, and nearby France in particular.

Thesis 74

I have therefore added the sextile, as well as the conjunction of Jupiter and Mars because they affect certain political horoscopes. Thus they will be active in this year; whether happily or unluckily (as God wills) they themselves may judge.

Still, the fiery planet Mars can afflict a person's natural disposition, if he or she is not exceedingly strong, when it wanders around Virgo for a long time, and when in opposition to the sun in March it disturbs the natal day.


KEPLER ON ASTROLOGY

Thesis 75

I know that astrologers are accustomed to predict the death of some outstanding military leader from the conjunction of Jupiter and Mars, which falls on the seventeenth of Libra, especially if he should have some particular disposition of his horoscope there. Lest this practice be judged as slander, as if heaven might be said to be founded for afflicting mankind, it [the prediction] must be explained otherwise. For this is the true meaning: that since this aspect is fiery per se and is one of the bright planets, thus experience testifies that it is found in illustrious families.

But when almost every agitation of body or mind occurs, or a transition is made to a new status when heaven corresponds to the horoscope (which is especially evident in births), it often happens that some illustrious people are moved under these and similar aspects, since the number of people born under such aspects is so great. Indeed the very same agitation, just as it gives those badly disposed over to destruction, just so it moves the stronger ones, either by reason of age or health, to great accomplishments. And each of these groups can also become affected in opposite ways in this year, but nothing is clearly inevitable.

CONCLUSION I have dealt in this book with what I felt could

be discussed and defended about the fundamentals of astrology and about the coming year 1602 on the basis of physics. Now if the professors of physics think that these fundamentals are worthy of consideration, let them communicate their criticism to me, so that we may discover the truth; and I shall answer them, God granting me the faculty, with prognostics for the following year. Furthermore, I urge all those philosophizing seriously to participate in the effort. For it involves the honor of God the Creator and the advantage of the human race. Meanwhile I heartily wish one and all a Happy New Year through Christ our Mediator.

GLOSSARY OF PROPER NAMES OF PERSONS AND PLACES

Aratus (ca. 315-240/239 B.c.): He composed an astronomical poem entitled Phaenomena, of which one section deals with weather signs (Prognostica). This work was widely read by both Greeks and Romans until the end of antiquity. Hipparchus (ca. 190-120 B.C.), the great Greek astronomer who was held in such high esteem by Ptolemy, wrote a commentary on this poem. It is, in fact, the only existing work of Hipparchus, who is otherwise known to us largely through the writings of Ptolemy. Aristotle (384-322 B.C.): The works of Aristotle provide the major link between Greek science and

philosophy and the scholarship of Europe during the second millennium. They form the basis of the scholastic tradition in which Kepler was trained and the tradition in which he argued for change (see Notes 17 and 32). English translations of his entire works can be found in the Loeb Classical Library (Rackham, 1945) or in The Works of Aristotle Trans- lated Into English, edited by W. D. Ross, which also appear in Volumes 8 and 9 of The Great Books of the Western World.

Brahe, Tycho (1546-1601): Kepler joined Tycho in Prague at the beginning of 1600. He was the major source of the astronomical data used by Kepler (in particular, the data on Mars was the key to Kepler's New Astronomy). Tycho had constructed observing equipment of heroic proportions, and his data, good to about two minutes of arc, was almost an order of magnitude better than that of Ptolemy. The best biography is by J. L. E. Dreyer (1963), who also edited the collected works of Tycho (Dreyer, 1913). Partial English translations can also be found in Boas, 1959 and Shapley, 1929, pp. 18-19. See the entry in this Glossary under Rosenberg for a description of Tycho's death.

Bulder, D. Herman (contemporary of Kepler's): As described by Kepler, he appears to have been an astrological consultant of sorts to Baron von Rosen- berg, to whom this work is dedicated.

Caesius Bassus (First Century A.D.): He is mentioned in the life of the Roman satirist Persius (Satire 6) as one of his intimate friends; he is classed with Horace as a lyric poet by the Roman educator Quinti- lian in his Institutio Oratoria (10.1.96); Caesius was killed, according to the Scholia, in the famous eruption of Vesuvius. (Conington, 1893).

Cardanus (Cardan, Jerome) (1501-1576): Although he wrote more than 200 works on medicine, mathematics, physics, philosophy, religion, and music, his fame today rests on his contributions to mathematics. In 1570, Cardan was imprisoned by the Inquisition. He was accused of heresy, particularly for having cast the horoscope of Christ and having attributed the events of His life to the influence of the stars. After a few months in prison, having been forced to recant and to abandon teaching, Cardan went in 1571 to Rome where he obtained a lifetime annuity from Pope Pius V. During the last year of his life he wrote an autobiography that, in the words of one observer, "did not shrink from the most shameful revelations." For Cardan's work in magic, alchemy, and the arts of divination, see Thorndike, 1923: v, pp. 563-579.

Cicero: (106-43 B.C.) : Prolific writer, lawyer, statesman, and philosopher, he was the first important prose

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author to introduce Greek philosophy to Roman read- ers, and he created a Latin philosophical vocabulary. Translated Aratus's astronomical poem, Phaenomena. His philosophical work On the Nature of the Gods contains information on the scientific knowledge of his time. In two other books, On Divination and On Fate, superstition is differentiated from religion, and determinism from fatalism. Cicero states that he was led to write his philosophical works through his determina- tion "to help his fellow citizens" and "never to stop seeking the good of the community." These works have had their main influence as practical guides to the good life. (Dorey, 1965).

Hesiod (Eighth Century B.C.): A didactic poet thought by the Greeks to be one -of the earliest teach- ers and civilizers of man, Hesiod composed two major poems. The first, Works and Days, is filled with moral precepts and contains a description of a year's farm work (farmer's almanac). Proper times for various operations are indicated by the positions of constellations, migrations of animals, etc. He also gives advice on navigation and names certain days lucky or unlucky for various operations. The other poem is the Theogony, the first work of conscious religious writing in Greek. These works and The Shield of Herakles (of disputed authorship) are available in translation. (Lattimore, 1959).

Kepler (1571-1630): It is generally conceded that the best biography of Kepler is that by Max Casper, first published in German in 1948. It is now available in an English translation by C. Doris Hellman (Casper, 1959). The English edition by Dr. Hell- man also contains an excellent bibliography of Keplerian studies and translations. An excellent shorter biography and a selected bibliography by Owen Gingerich appear in the Scribner Dictionary of Scien- tific Biography. An interesting popular biography of Kepler is The Watershed by Arthur Koestler (Koest- ler, 1961), which has been taken from the larger work, The Sleepwalkers, by the same author (Koestler, 1959). Both are now available in paperback editions.

Origanus, David (1558-1629): A teacher of Greek and mathematics at the Academy in Frankfort-on-the- Oder, Origanus compiled ephemerides for the period 1595 to 1655 that contained in the preface a listing of all the eclipses that were to occur in each year. Pico della Mirandola (1463-1494): An Italian hu- manist who argued against astrology on religious, philosophical, and scientific grounds (it denied the omnipotence of God, it denied free will, and it was strikingly inaccurate). He pointed out that the astronomical basis of astrology would be shattered when astronomers adopted the Copernican system, as he believed they would. (See Note 18). Pliny (A.D. 23-79): The elder Pliny was a Roman statesman who produced among other works, the

Natural History, a complete encyclopedia of the science of his period. Included along with geography, botany, biology, metallography, etc., were descriptions of the practice and utility of various forms of magic. The lion, the unicorn, and the phoenix were all described and accepted at apparently the same level of credulity. Pliny also notes, "It is generally admitted that all water is more wholesome when it is boiled," and his English translator of 1856 commented, "This is not at all the opinion of the present day." Perhaps the various cholera epidemics of the nineteenth century might have been prevented if we had not thrown out his boiled water with the unicorn.

Prague, Bohemia: A city in what is now Czechoslo- vakia. Kepler moved here at the beginning of 1600 to join Tycho Brahe. It was here that On the More Cer- tain Fundamentals of Astrology was written, as well as his great work on astronomy, The New Astronomy.

Ptolemy, Claudius (A.D. 100-170): The life of Claudius Ptolemy is almost unknown despite his fame as an astronomer and geographer. His works in astronomy (The Almagest) and in astrology (The Tetrabiblos) were used and preserved by the Arabs during the so called "dark ages" and served, along with Galen's work in medicine and Aristotle's work in biology and physics, as a major link between Greek science and European science of the second millennium. The only English translation of the Almagest appears in Volume 16 of The Great Books of the Western World (Ptolemy, 1952), and a translation of the Tetrabiblos is in the Loeb Classical Library (Ptolemy, 1940). Reinhold, Erasmus (1511-1553): After Copernicus, Reinhold was the leading mathematical astronomer of the sixteenth century, and in computational ability he surpassed Copernicus himself. In 1551 he produced the Prutenic Tables, which contained astronomical data based on calculations from the Coper- nican model. (Gingerich, 1973: pp. 43-62).

Rosenberg, Petrus Wok de (ca. 1600): "Peter Wok von Rosenberg was the leader of the Utraquists. As the last of one of the most powerful and richest families of Bohemia, he led a lavish life in splendor and luxury and squandered colossal sums on his alchemical passion. After Brahe's death, Rosenberg transferred his friendship for him to his successor. Kepler gave evidence of his gratitude by dedicating to him the first work he published after his change of residence to Prague. It was an essay about the more reliable foundations of astrology." [M. Casper, 1959: p. 161].

It was, in fact, at Baron Rosenberg's table that the great Tycho set the stage for his dramatic demise. Kepler reports in his Diary of Observations:

On 13 October, Tycho Brahe, in the company of Master Minhowitz, had dinner at the illustrious Rosenberg's table,


KEPLER ON ASTROLOGY

and held back his water beyond the demands of courtesy. When he drank more, he felt the tension in his bladder increase, but he put politeness before his health. When he got home, he was scarcely able to urinate.

At the beginning of his illness, the moon was in opposition to Saturn . .. [follows the horoscope of the day]. After five sleepless nights, he could still only pass his

water with the greatest pain, and even so the passage was impeded. The insomnia continued, with internal fever gradually leading to delirium; and the food he ate, and from which he could not be kept, exacerbating the evil. On 24 October, his delirium ceased for several hours, nature conquered and he expired peacefully among the consolations, prayers and tears of his people. [Koestler, 1959: p. 315].

Stoeffler, Johannes (1425-1531): A professor of mathematics, astronomy, and geography at Tubingen. He published an account of an astrolabe of his own construction and other scientific works.

Theophrastus (372/369-288/285 B.C.): Peripatetic philosopher, scholar, teacher, and writer, he was Aristotle's successor as Head of the Lyceum. He continued Aristotle's encyclopedic purpose, and his activities were prodigious. In addition to his great work on the history of physics, he wrote scientific treatises on meteorological subjects, such as "On Weather Signs." The Characters is a popular collection of thirty brief character sketches describing human foibles in exaggerated descriptions (the avaricious person, the loquacious person, etc.). Kepler probably alludes to this work in his term "full of fables" (Thesis 46). A translation of the Characters is found in the Loeb Classical Library (Edmonds, 1929).

Virgil (70-19 B.C.) : A great Roman poet and leading naturalist of his time. In addition to his epic, the Aeneid, and the pastoral poetry of the Eclogues, Virgil also wrote an outstanding scientific treatise, the Georgics. It is divided into four books: 1, agriculture in general; 2, trees, especially vines and olives; 3, stock farming; and 4, bee-keeping. These works, as well as minor poems, are translated in two volumes of the Loeb Classical Library (Fairclough, 1930).

NOTES

FOREWORD AND PREFACE

Note 1. Neugebauer, 1969: p. 171. Note 2. Ptolemy, 1940: p. 3. Note 3. LaPlace, 1829: p. iii. Note 4. Duhem, 1969: p. 5. Note 5. Neugebauer, 1969: p. 204. Note 6. Kepler, 1952: p. 850. Note 7. Kepler, 1952: p. 926. Note 8. Simon, 1975: p. 446. Note 9. Kepler, 1858. Note 10. Kepler, 1938 4: pp. 8-35. Note 11. Casper, 1959: pp. 391-396. Note 12. Gingerich, 1973: pp. 289-312.

NOTES ON TRANSLATION

SECTION ONE

Note 13 (Thesis 6)

The time of elevation of the winter sun, 7 hours and 49 minutes, is correct (as is demonstrated below). Thus the length of time the winter sun is set is 24 hours minus this time or 16 hours and 11 minutes, which is just about twice the time of elevation. Since in summer the situation is reversed, it would therefore appear that the time of elevation of the summer sun is 16 hours and 11 minutes not 22 minutes as given here.

The first drawing is a hemispherical cross section that locates Prague at noon on the summer solstice, The earth's axis is inclined at an angle of 23.5? with respect to the plane of the earth and the sun; Prague has a latitude of 50.096? (50? 5' 45"). The line CC' is the projection on the cross section of the great circle on the earth that represents the border between light and dark. The point p is the intersection of the line AB and the line CC'.

Earth s location of Prague at noon on

\s the winter solstice)

Border between light and dark

The second drawing is a cross section of the earth, sliced from point A to B (Prague) in the preceding drawing. The arc ab taken in a clockwise sense represents the angle for which Prague is dark in the summer. (Recall the meaning of the point p from the previous drawing.)

B q

a U- -0

96

VOL. 123, NO. 2, 1979] 107

0-

b.-

a

BRUCE BRACKENRIDGE

Thus one has from the second drawing

cos OD = qP/qA

and from the first drawing

qA/r = sin 39.904? = 0.64150

or

qA = 0.64150r.

Further

qO/r = cos 39.904? = 0.76712

or

qO = 0.76712r.

Finally

qP/qO = tan 23.525? = 0.43532

or

qP = 0.33394r.

Thus the cosine of OD is given by

cos OD = qP/qB = 0.33394r/0.64150r = 0.53057

or

20D = 117.258?

The time TD the summer sun is set is given by

117.2580 TD = 117.2 X 24 hours = 7 hours 49 minutes 3600

and the time TL summer sun is risen is

TL = 24 hours - TD = 16 hours 11 minutes

Thus the relative height of the summer and winter sun in the proportion of the angles of incidence at noon, or

63.40 Ratio 16.4 = 3.87 or approximately four times.

Note 15 (Thesis 10) The combined effect is the product of the two ratios;

thus the winter heat is diminished by i due to the decreased time of elevation and by - due to the obliquity of the sun's rays or a product of -.

Note 16 (Thesis 11) For this calculation we assume the German mile

to be the order of 3 or 4 English miles. Thus the radius of the earth is roughly 1000 German miles. The following figure again shows the summer and winter drawing of the earth's atmosphere.

The effective thickness of the atmosphere at noon on the summer solstice is the distance AB'. From the law of sines one has

Note 14 (Thesis 10)

The following drawing is the same as the first cross section in Note 1. At point A it gives the angle between the horizon and the sun's rays at noon in Prague for the winter solstice (16.4?) and at point B for the summer solstice (63.4?).

sin 153.429? sin Z OB'B OB' OB

where

Thus

OB' = 1001 German miles and

OB = 1000 German miles.

1000 sin Z OB'B = 1001 (sin 153.429?) = 0.44686 1001

thus the angle is given by

ZOB'B = arc sin 0.44686 = 26.542?

The angle BOB' is given by

Z BOB' = 180 - 153.429? - 26.542? = 0.029?

Again from the law of sines

sin 0.029? sin 153.429? BB' 1001

The ea]th's axis


on

KEPLER ON ASTROLOGY

OR

/ sin 0.029? \ /0.0005061\ BB' =

1001sin 153.429?) = 1001 0.4473 = 1.1 German miles

Which is the one and one ninth (1.1) given by Kepler. Repeating the calculation the winter thickness AA'

sin 106.379 sin Z OA'A 1001 1000

OR

1000 / OA'A = arc sin 1001 (0.95942) = 73.427?

Thus the angle AOA' is given by

Z AOA' = 180? - 106.379? - 73.427? = 0.194

sin 0.194? sin 106.379 AA' 1001

OR

0.003386 AA' = 1001 = 3.5 German miles

0.9594

which is a bit more than three and a third (3.3) German miles for the winter thickness given by Kepler. In any event, if one assumes that the ratio of the effective thickness is about 1, and then multi- plies by the factor of -1 from the three other causes discussed in Thesis 10 (see Note 15), one has a "twenty-fourth part of the summer heat that remains in winter."

Note 17 (Thesis 20)

Aristotle's discussion of the four elements (air, earth, fire, and water) appears in the third of the four works that comprise the body of his "physical science." (Physics, On the Heavens, On Coming into Being and Passing Away, and Meteorology). In the first work contraries are established as principles in natural philosophy and, in the general sense of Excess or Deficiency (similar to the Same and Different employed by Plato in the Timaueus), are refined by Aris- totle into the principal contraries of Form and Priva- tion.

In the third work, the tactile sense is identified as by far the most important of the senses, and four qualities, the "tactile sense contraries" of hot, cold, wet, and dry, are introduced to derive and explain the behavior of the four elements. These four elements, and in fact these four qualities, had long been employed by Greek natural philosophers. What is new is that Aristole assigns two qualities to each element (earth is cold and dry, water cold and moist, air moist

and warm, and fire dry and warm), and he permits one element to transform into another by replacing one quality with its contrary.

In the section to follow, Kepler must supply a physical model to account for the astrological powers of the planets. To do so (see Note 18) he requires three degrees of heat and three degrees of warmth; the Aristotelian system of two degrees of each does not supply him with enough options to describe all five planets. Thus he appeals to geometry for the existence of a mean between the two extremes to provide the needed versatility.

Note 18 (Thesis 24)

The astrological powers of the various planets (i.e., Mars is hot and dry, while Venus is warm and moist) have been well established by their "successful" usage over the ages. What is in question here is not the validity of the choice of particular powers but rather how they are to be reasonably derived. Ptolemy accounts for them by the planet's proximity to the two luminaries, the sun and the moon, and to the moist exhalations about the earth. [Ptolemy, 1940: p. 35] Ptolemy, however, places the earth at the center of the system and arranges the luminaries and the planets in order of their periods of motion about the earth (the longest period is assumed to represent the most distant planet); arranged in this way, the sequence is: the moon, Mercury, Venus, the sun, Mars, Jupiter, and Saturn. Thus Mars and Venus are similar in warmth by virtue of their proximity to the sun; they differ in moisture, however, since Mars is removed from the moon while Venus is relatively close to it.

Kepler, however, has adopted the Copernican system in which the sun and earth exchange places (sun, Mercury, Venus, earth and moon, Mars, Jupiter, Saturn). Thus, Mars is not only removed from the sun, but is in fact very close to the moon. Neverthe- less, Mars must still be hot and dry because astrological experience has shown that it is hot and dry. Kepler is to offer physical reasons to supplant Ptolemy's luminary proximity based upon the optical properties of the surfaces of each planet (these are discussed in the Theses 25-30). The chart that is given here in Thesis 24 simply displays the astrological powers of the planets and attests to their uniqueness. Critical to this ordering is the inclusion of a mean state between the two Aristotelian states of excess and defect (see Note 17). This chart, however, appears in part to be at odds with the text. Since the chart was set by the printer and since it contains a complicated and convoluted set of interworked words, perhaps it is not unreasonable to assume that it may contain typographical errors.

The following is the chart as it appears in the

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original Latin text:

Sol. u 4- 0)

u

Excessus I V P I T E R

S mer S S

A cu V R

T N ri A

VE V M us

Mediocr. I V P I T E R

mer S R S

Rcu V N

A N ri V

M VE cu S

Defectus I V P I T E R

Excessus -

Mediocritas )

Defectus

there appears to be some contradiction within the text itself as well as between the chart and the text.

The chart for Mars and Saturn, however, is clearly in error. They are shown as follows:

m

E 0, CL h*

Luna.

From this chart a simplified version of the chart for Mercury and Venus can be constructed:

EE

60

Su K

r:

. Moon

oq

These are the combinations of warmth and humidity that are referred to in Thesis 24 as "two-as already explained-in a way twofold, but really with two names." They have been previously described in this thesis as follows: "Two pairs of these combinations are reduced to the same thing. For there is the same proportion between excess of heat and mean of humidity as there is between mean of heat and defect of humidity."

The chart for Jupiter can be redrawn as follows:

Excess

Sun e I Mean

Defect L.

Thus Mars would be cold and moist and Saturn hot and dry; clearly this drawing is at odds with all that has gone before and all that is to follow since "Saturn exceeds in humidity (and) is deficient in heat." [Thesis 30] Note, however, that Saturn's function is described by Ptolemy as "chiefly to cool and moderately, to dry, probably because he is fur- thest removed from both the sun's heat and the moist exhalations of the earth." [Ptolemy, 1940: p. 35] In this description of Saturn's dryness, Kepler is moderately at odds with Ptolemy.

Also there is confusion concerning the number of true variations. We are told in Thesis 24 that "there are, then, five true variations, three simple, two . . . in a twofold way, . . . and one with three." Since the twofold and threefold have to be identified with Venus, Mercury, and Jupiter, the simple variations appear to be those associated with Mars and Saturn (simple in the sense that there can only be one transition for each). Further, if there are only two simple variations instead of three, one has the proper sum of five possible variations.

It would appear then that the correct drawing for Mars, Saturn, and Jupiter should be as follows:

Excess

Sun U N Mean

Defect

K

Jupiter

< Jupiter

Jupiter

Excess

Mean > Moon rt

Defect

/

It would appear from the text, however, that there should be only one line for Jupiter: that line from mean heat to mean humidity. We are told in the opening of Thesis 24 that "Excess may not be accumulated readily, nor may defect. . . . And so no planet has been made that received either an excess of both or a defect of both." In the next paragraph of this thesis, however, we are told that one of the five true variations has one name but with a threefold variation, presumably Jupiter with the three levels. Thus

Excess Excess

Sun E Mean piter Jupiter Mn oo

DefeDefect Def

Note 19 (Thesis 25)

Here Kepler is arguing that if planets only reflect light, then they should show phases, such as the moon. He is soon to change his opinion, however. By 1609 Galileo employs his telescope to view the planets, and soon the phases of Venus are established. In his Letters on Sunspots, Galileo states, "The opaqueness of Venus is indubitably proved by the single experience I reported in my first letter (The Starry Messenger, 1610): namely, our seeing Venus vary in shape as

Moon


r

KEPLER ON ASTROLOGY

does the moon." [Drake, 1957: p. 153] Kepler recognizes and accepts this new evidence in his Dissertation on the Starry Messenger. The planets, like the moon, are opaque; only the sun and the fixed stars emit their own light. There is, however, some indication that Kepler had earlier begun to change his mind on this issue. In 1607 he had considered in a letter the assumption that the planets might be opaque like the earth and, in fact, might even be inhabited. In this work of 1601, however, he clearly adopts the position that planets both radiate and reflect light.

Note 20 (Thesis 26)

The Aristotelian position requires that the moon and all objects beyond the lunar sphere be perfectly spherical. Kepler argues here that if the surface of the moon were of a hard, smooth, mirror-like quality we would not see the entire surface illuminated but rather we would see the image of the sun only as a bright point. Later, Galileo also makes use of this argument. [Galileo, 1970: p. 70]

Note 21 (Thesis 27)

In what is to follow, Kepler develops an early version of a subject that is to be of interest to him throughout his life: the explanation of the colors of the rainbow. Here he divides the rainbow into two equal sections and offers a different physical cause for each half. The common source is light itself, or to be more precise "a white glow analogous to light" which occupies the middle of the rainbow. Since the center of a single rainbow is in fact not white, the "source" itself is not visible, but only its effects.

Note 22 (Thesis 27)

The colors on this side of the rainbow are attributed to obfuscation, or in contemporary terminology, "scat- tering." The current explanation for this effect has light scattered by particles in our atmosphere, the short wave lengths (blue) are scattered more than the long wave lengths (red). Hence "the sky is blue." As the sun sets, its rays must pass through more and more of the atmosphere, and hence more and more blue is scattered from the white light leaving it to appear first yellow and then red. Kepler does not offer such an explanation but he is well aware of this effect as one way by which white light (the white noon day sun) can be transformed into colors (the red setting sun).

Note 23 (Thesis 27)

Theories of the rainbow have long been a topic of interest. Aristotle discussed the rainbow in terms of the reflection of light; in the middle ages Grosseteste and others interpreted it as a refraction phenomenon;

and as late as the beginning of the twentieth century it served as a doctoral dissertation topic for the physicist Debeye.

Kepler here is discussing the colors of the half of the rainbow referred to in the third sentence of this Thesis as the class due to "refraction" (refractione). Here, however, he attributes it to "reflection" (re- flexionis). Perhaps he simply anticipates the "rainbow-reflecting surface" analogy that is to follow (see Note 24). With either term, reflection or refraction, problems can be posed. If he does intend to attribute this half of the rainbow to "reflection," then the refractive properties to follow are not explained by the rainbow but rather must be used to explain it. If he does intend to attribute this half of the rainbow to "refraction," then the result can demonstrate, by analogy, the reflective properties of surfaces. Moreover, the portion of the prismatic colors that would arise from refraction appear in the order given: green, blue, and purple. Why, however, does he attribute only half of the spectrum to refraction ? Why does refraction not also account for the yellow and red half of the rainbow that were described as being due to obfuscation (see Note 22) ? Boyer says, "Kepler here seems to use the term refraction in the Aristote- lian sense of reflection." [Boyer, 1950: p. 362]

Note 24 (Thesis 27)

Here an analogy is proposed between reflecting surfaces and the rainbow with its two classes of colors, one a product of (due to) absorption and the other a product of (due to) refraction (reflection?). The ability of a surface to reflect is derived from the colors in the rainbow: the best reflector is a bright surface and corresponds to the bright center of the rainbow, which although it is not seen to be white, nevertheless corresponds to white (see Note 21) ; second are surfaces corresponding to the next color on either side of the center (yellow and green); third in ability to reflect is the next pair (red and blue); fourth is the next pair (purple and dusky); and last is the black surface corresponding to black at either extreme.

The Traditional Prismatic Colors

Red

Orange Yellow

Green Blue

Violet

Kepler's Description of the Rainbow

Black

Absorption Red usk

Yellow (White) I Reflecting (WhitePi Green I Pairs

Refraction i Bluea -

Purple+-- Black

Note 25 (Thesis 28) The color of the planets may be described in general

terms as follows: Saturn is dull yellow, Jupiter has

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BRUCE BRACKENRIDGE

irregular bands of yellow and bluish or brownish grey, Mars is ocher or greyish red, Venus is slightly yellow, and Mercury is copper-hued.

Note 26 (Thesis 32)

When discussing the ability of the sun to heat (Thesis 9), we were told that it "warms more when it is high than when it is low." In that instance "high and low" referred to the angle the sun's rays make at noon (see notes 13 through 16). In this case "high" and "low" appear to refer to something else, since for planets, "the greater angle at which they are seen (i.e., low) so much more heat do they give." One possible explanation might be that "low" refers to a planet that is close to the earth and hence able to heat more, while "high" refers to a more distant planet. Consider the following sketch of the sun and earth with Mars shown in two positions, conjunction and opposition.

Mars

For a Large Angle "low" = near

For a Small Angle "high" = far away

The difficulty in this description is that for either near or far, the angle subtended by the planet is so small as to defy comparison except in the abstract (i.e., it would be difficult to observe a variation with the naked eye).

The final sentence, "But the power that is increased by height has another cause," may well refer to the geometric cause, that of aspects, to follow in section two.

Note 27 (Thesis 33)

The sun enters into Cancer on the summer solstice. Hence the time of elevation, nature of the atmosphere, and the angle of obliquity all conspire to increase the effect [see Theses 3-11 and Notes 13-16].

SECTION TWO

Note 28 (Thesis 36)

A geometric angle is one that can be constructed with a straight edge and compass. For example, a 60? angle can be formed by generating an equilateral triangle and then bisecting or doubling as often as de- sired. Or, a 180? angle (a straight line) can be bisected into a 90? angle and thence into a 450? angle, etc. One can also construct a pentagon and thus get multiples of angles of 72?. A harmonic angle is one that is related to eight harmonic ratios of motion (to be discussed in Thesis 38 and Note 30). Specifically, it is one of the eight aspects Kepler employs in his predictions (0?, 36?, 600, 72?, 90?, 120?, 135 , and 180?).

Note 29 (Thesis 37)

The full title of this work is the Precursor of Cosmographic Dissertations or the Cosmographic Mystery, and it is Kepler's first great work, published in 1596. Although the opening chapter sets forth very strongly and clearly Kepler's reasons for aban- doning the Ptolemaic system in favor of the Coper- nican system, the major importance of the work is its attempt to provide the first step in revealing the universal harmony that Kepler was convinced existed in planetary structure. What Kepler sought throughout his entire professional life was to discover the geometrical laws that were involved in the distribution and motion of the planets. He is now best remembered for his three laws of planetary motion, perhaps because it is this portion of his work that was of interest to Newton in the opening section of the Principia and hence of interest to eighteenth and nineteenth century physicists. In any event, Kepler himself takes as much if not more pride in the order revealed in this work, The Cosmographic Mystery, and in his later work, The Harmonies of The World, than in his now famous three laws of motion (which do not appear explicitly under that title but are distributed throughout his work on Mars in 1609 and in his later works).

The specific problem that he addresses in the Cosmographic Mystery is that of the location and number of the planets. Why are there only five planets and why are their relative orbits as they are? The solution, he reports, came to him during a lecture while he was drawing a figure of the cycles of the great conjunction of planets. There are only five regular solids-three dimensional figures with identical faces that all join at the same angle: e.g., a cube-and five intervals between the six celestial spheres. Kepler envisioned a system of spheres circumscribed and inscribed about the regular solids. Such a system has the correct number of orbits and could be tested for the relative size of the orbits. Employing the values


KEPLER ON ASTROLOGY

for the radii of the planetary spheres given by Coper- nicus, Kepler found that a "reasonable" fit could be made between the spheres and the regular solids in the following order: Saturn, cube, Jupiter, tetrahedron, Mars, dodechedron, the earth, icosahedron, Venus, octahedron, Mercury. The data fit is close enough to be suggestive but imperfect enough to require further effort. Unlike his "three laws of motion," improved data tended to discount this law of planetary pack- ing. In the ninth chapter of the work he derives the astrological qualities of the five planets from the nature of the five solids.

Note 30 (Thesis 37)

In 1619 Kepler published under the title The Har- monies of the World a work that was in effect the sequel of his Cosnmographic Mystery (see Note 29). Now, however, he had Tycho's very accurate data and it was clear that the construction of the six planetary spheres from the five regular solids was at best approximate. Also, Kepler had analyzed the data for the motion of Mars as well as for the spacing of the planets, and in 1609 in The New Astronomy he had derived the elliptical orbit and equal area laws: the two relationships now referred to as Kepler's first and second laws. In the Harmonies of the World the data are further analyzed and the third law emerges: the square of the period of a planet about the sun is proportional to the cube of the mean distance from the sun. The work, however, contains much more. It is a hymn to geometry; God the Creator is the Geometer and speaks in the universal language of geometry; the heavens abound in harmony expressed in planetary motion and positions that can be recited and revealed in the harmonies of music. Each planet has its own range of notes derived from the ratio of diurnal arcs at aphelion and perihelion. Thus, on the one hand, Mercury, with its great eccentricity, has a wide range of notes. The earth, on the other hand, with an almost circular orbit, is restricted to sing simply mi, fa, mi. Such a song is nevertheless consistent with Kepler's view of this demanding world: "The Earth sings MI, FA, MI, so that you may infer even from the syllables that in this domicile MIsery and FAmine obtain." [Kepler, 1939: p. 1040.]

In particular, Kepler must find the correct index of celestial motion in which to express the innate harmonies, i.e., the eight harmonic ratios of motion. He considers five options, including the distances from the sun and the periodic times, but concludes that it is the diurnal arcs of the planets at perihelion and aphelion, as seen from the sun, that is the correct factor. Tables of these arcs are constructed from Tycho's data, and ratios are taken from all possible combinations (Jupiter at perihelion to Saturn at

aphelion, etc.). The test that these ratios must pass in order to be adjudged correct is that they prove to be consonant and that the single consonances (ratios) do not "stand so separate that they have no kinship with the rest." In fact the ratios must all join together "in one octave of thenl which embraces the rest in power . . . in such a way that there would be a [musical] scale." [Kepler, 1939: p. 1035.] Such a scale is found to exist and although various ratios have to be transposed two or three octaves to overlap, success is assured and the fundamental number of ratios of motion is set at eight, to conform to the octave.

This correspondence between celestial motion and musical scales does not come as a surprise to Kepler, for as he says "Accordingly you won't wonder any more that the very excellent order of sounds or pitches in a musical system or scale has been set up by men, since you see that they are doing nothing else in this business except to play the apes of God the Creator and to act out, as it were a certain drama of the ordination of the celestial movements." [Kep- ler, 1939: p. 1038]

Note 31 (Thesis 38)

When the two luminaries, two planets, or a planet and a luminary are in the same angular position aspect in the zodiac, they are said to be in Conjunction: i.e., their angular difference is zero. When they are on opposite sides of the earth, their angular positions in the zodiac differ by 180? and they are said to be in Opposition. In Quadrature, Trine, and Sextile the angular positions in the zodiac differ by 90?, 120?, and 60? respectively. These are the five aspects that have traditionally been employed by astrologers. The three additional aspects added by Kepler are quintile, a fifth part, or 72?; biquintile, a half of quintile or 36?; and sesquiquadrature, one and a half of quadrature, or 135?.

Kepler claims that "reason led" him to make the addition and that "many experiences have since confirmed the choice." The "experiences" are obviously successful predictions made on the basis of the new aspects. [See, for example, the predictions for January in Thesis 52.] The "reason" that led him to add "three more" aspects to the traditional five evolved from his long time concern with geometry, aspects, and muscial consonance. As was made manifestly clear in all his work (see Note 30), geometry was for Kepler the key to understanding. It was revealed in all of God's work, astronomical, astrological, or musical.

In music, the beauty and fullness of geometry was most clearly demonstrated in the consonances or harmonies: the fundamental rates of notes that produce "harmonic" or "pleasing" sounds. These funda-

113 VOL. 123, NO. 2, 1979]

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mental ratios have had different values at different times and in different cultures. For the Pythagoreans, the fourth (4: 3) was the smallest consonance. According to Ptolemy the intervals could be ranked in three categories of consonance: "the octave and double octave are most satisfying to the human ear; the fourth, fifth, eleventh, and twelfth next; the last group includes the tone, the thirds, and the sixths." (Bowden, 1974) p. 118. For Kepler, however, the fundamental musical ratios were those of the "just" intonation of the renaissance: 2:1 (octave), 3:2 (fifth), 4:3 (fourth), 6: 5 (minor third), 5:4 (major third), 5:3 (major sixth), and 8:5 (minor sixth).

In astrology, the beauty and fullness of geometry was most clearly demonstrated in the power of planetary aspects or juxtapositions. An aspect is the angle between two celestial objects. Thus when Mars and Jupiter are separated by 120? along the zodiac they are said to be in trine: one third of a full circle. But there is an unlimited number of such angles and the astrologer had to select the "correct" ones to use in his prognosis. For Kepler, it was a correspondence between the major consonances and the major aspects that supplied the "reason" for his selec- tion. This idea was not new with Kepler; rather it was the emphasis placed on aspects and their relationship with music that distinguished him from Ptolemy, for example. For Ptolemy, "tuning entered into the aspect theory only marginally; it depended mainly on the common ground of the Pythagorean and Ptolemaic octave, fourth, fifth, and twelfth. . . . The general procedure consisted in generating ratios from the aspects by comparing the arcs of circle so cut off and then correlating these with harmonic ratios." (Bow- den, 1974: p. 118.) Thus when two celestial objects are said to be in trine, the angle between them is 120? and the arc cut off is 240?. Thus its ratios with the full circle is 360? to 240? or 3: 2 and its correspondence in music is to a fifth (3:2). For Kep- ler, however, the consonances were those of the "just" intonation, and just as "the ear is stimulated by harmony [consonances] . . . so the earth is stimulated through the geometric concourse of vegetating rays [aspects]" Thesis 43. Thus since there were seven consonances in the "just" scale, so there must be seven aspects in the astrological system. In the Mysterium Cosmographicum Kepler states:

monic ratios of the just scale as follows: (Bowden, 1974: p. 153.)

OPPOSITION 2:1 OCTAVE TRINE 3:2 FIFTH

QUARTILE SEXTILE 4:3 FOURTH 6:5 MINOR THIRD

The fifth traditional aspect is conjunction and would correspond to a ratio of 1: 1 or perhaps unison. The three new aspects suggested by Kepler are related to the three remaining harmonic ratios as follows: (Bow- den, 1974: p. 153.)

QUINTILE 5:4 MAJOR THIRD

BIQUINTILE 5:3 MAJOR SIXTH

Therefore since all four harmonies agree with their aspects, and in fact three harmonies remain in music, I have a suspicion that it should not be neglected in judging of nativities if the planets are 72 or 144 or 135 degrees apart, especially since I see that one of the imperfects has its aspect. (Bowden, 1974: p. 119.)

Thus the four traditional aspects employed by astrologers are related by Kepler to four of the har-

SESQUAQUADRATE 8:5 MINOR SIXTH


KEPLER ON ASTROLOGY

However the events of 1602 supported his new aspects, they failed in the long run. As Bowden states:

This beautiful unitary structure was destroyed by the meteorological research he had advocated. Several of Kepler's contemporaries set about making weather observations to test new aspects. Unconstrained by Kepler's harmonic predilections, his followers were more open- minded in finding correlations between angles and the weather. At least in some cases this freedom was owing to a misprint. According to Kepler's account of 45? instead of 135?, "sequadrum," instead of "sesquadrum," thinking "semi" instead of "sesqua." Kepler credited his old teacher Mastlin with suggesting the possibility of aspects beyond the three Kepler had added. In late 1607 Kepler converted to this conclusion. The sesquaquadrate did not correlate at all well with the weather, but the "semisextile' (30?) did. This was the long avoided separation of one sign, which had little to do with music. (Bowden, 1974: pp. 121, 122.)

Note 32 (Thesis 42) For Aristotle that which is in possession of life is

in possession of a soul. There are, however, several connotations for the word life: intelligence (capable of thought), sentience (capable of sensation), mobil- ity (capable of spatial movement and rest), and the processes of nutrition (capable of growth and decay).

Plants have only the faculty of nutrition. All animals possess in addition to the faculty of nutrition, at least one faculty of sentience, namely touch. Finally, there is a small fraction of living things that possess in addition to sentience and nutrition the faculty for understanding and the power to reason. Thus, there are three levels of soul: plant, animal, and human. Since, according to Kepler, the earth is none of these yet it is sensitive to geometry, it must be assigned a fourth type of soul: i.e., the animate faculty.

Note 33 (Thesis 49) We are grateful to Professor Owen Gingerich, the

reviewer of the original manuscript, for the following point of clarification:

What Kepler is actually alluding to is the fact that both the Alfonsine (Ptolemaic-based) and the Prutenic (Coper- nican-based) Tables have a systematic error of half a degree in the position of the Sun, not corrected until the work of Brahe. Because the Sun moves approximately 1? per day, this error in the solar position gives an error of approximately 12 hours in establishing the time of the equinox. Since the horoscope drawn at the time of the vernal equinox is of fundamental importance in establishing the "Lord of the Year" this means that the ascendant is almost completely reversed and all of the houses turned about 180? around by the astrologers who were attempting to establish the character of the entire year from this critical horoscope.

Note 34 (Thesis 71) The city of Eger, known by the Latin name of

Agriensis and the German name of Erlau, was cap- tured by the Turks in the year 1596. When the Arch- duke Maximilian attempted to recapture it, a battle

ensued with great loss of life. His army was de- feated and retreated in great disorder.

Note 35 (Thesis 71) The wedding was that of Henry Bourbon, King of

Navarre, and Margaret Valais, the sister of Charles IX of France. It was at this time that the massacre of the Huguenots occurred on St. Bartholomew's Day (August 23-24, 1572).

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