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NUMBERS, PROGNOSIS, AND HEALING: GALENON MEDICAL THEORY

Published in: Journal of the Washington Academy of Sciences,

vol. 90, No. 2, Summer 2004, 4560.

Although science in the modern sense is, strictly speaking, a creation of Greek

thinkers, it is becoming increasingly clear, with the gradual recovery of data from the ancient

Near East and China, that science has far earlier antecedents. The impulse to gather data and

to anticipate the future is at least as old as civilization itself, and must have had survival

value in pre-historic hunter-gatherer and early agricultural societies. The earliest forms of

scientific reasoning are found in the practice of divination.1 Ancient science of all periods

emphasized the empirical: numerous archives have been discovered that contain records of

diviners observations, whether from sheep entrails or planetary observations in

Mesopotamia, or from oracle bones in Shang China, or from physicians clinical observations

in Egypt. Some texts (much fewer) offer explanations, attempting to connect the sign with

the thing signified by it. The Hippocratic Collection2 of medical texts (beginning 5th C. BC)

is among the earliest that adopts a full-fledged empirical stance toward observation while

attempting to derive naturalistic causal explanations. An oft-cited example is the treatise On

the Sacred Disease3

, the first recognizably scientific attempt to explain epilepsy. Seizuresare not due to the actions of gods or demons, the text explains, but are a perfectly reasonable

consequence of natural physiological factors. Occasionally we find texts in which the author

shows us how he derives the theory from the data. These texts are of special interest, since

they show stages in the development of scientific reasoning.

1 See, for example, Jean Bottro, Divination and the Scientific Spirit, Chapter 8 of Mesopotamia: Writing,Reasoning, and the Gods. Translated by Zainab Bahrani and Marc van de Mieroop. Chicago: University ofChicago Press, 1992; and Wolfram von Soden, Sumerian and Babylonian Science, Chapter 11 ofThe AncientOrient: An Introduction to the Study of the Ancient Near East. Translated by Donald G. Schley. Grand Rapids,MI: Eerdmans, 1994.2 The historical Hippocrates dates to the 5 th Century BC. However, most of the texts attributed to him were

probably written by his followers subsequent to that time. See Lloyd, G. E. R. The Hippocratic Question. In

Methods and Problems in Greek Science, 194-223. Cambridge: Cambridge University Press, 1991 (1975); andJouanna, Jacques. Hippocrates. Translated by M. B. DeBevoise. Baltimore, London: The Johns HopkinsUniversity Press, 1999 (1992).3De morbo sacro, The Sacred Disease, in Hippocrates.Hippocrates Volume II. Translated by W. H. S. Jones.Edited by G. P. Goold. Vol. 148,Loeb Classical Library. Cambridge: Harvard University Press, 1923. Reprint,1992, pp.129-183.

GLEN M. COOPER,NUMBERS, PROGNOSIS, AND HEALING: GALENONMEDICAL THEORY Page 1 of 15


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The treatise On the Critical Days4 by the physician Galen of Pergamon (AD 129-

c.216), who was the most important follower of Hippocrates, is such a text. The naturalistic

explanation he offers for the recurring seizures in certain illnessesthe motion of the moon

and the influence of its phaseswould not, of course, be considered valid today. But his

account is consistent with a scientific tradition of invoking celestial causes that extends back

to Aristotle (384-322 BC).5 Galens scientific method is the rational scaffolding around

which he builds a theory of the critical days. The critical days were one of the Hippocratic

rational schemes for prognosis. There are frequent references to them in the Hippocratic

literature, namely in the Prognostic6, theAphorisms7, and the Epidemics8; however, these

treatises include no explanation of how to use them or why they were supposed to work.

(The Epidemics are among the first medical casebooks, and have long been admired, even

today, for their dispassionate and scientific style of observation).

The steps of Galens derivation of his theory can be fruitfully compared with modern

scientific method. This shows that there were examples of recognizably modern scientific

reasoning is much earlier than is usually thought. This surprising fact may be obscured by

the nature of Galens scientific explanation: his approach resembles astrology to a degree

perhaps unsettling to us. Yet, the outline of his reasoning is familiar, as I shall show

presently. The early affinity of science with divination should not worry us. Medicine (and

weather forecasting) retains traces of their ancient divinatory origins: the termprognosis

itself (foreknowledge) evokes a sense of the divinatory or propheticthe physician and the

4De diebus decretoriis. The Greek text of this treatise is found in C. G. Khns edition of Galen, volume 9,pages 769941. (Throughout this article, I shall refer to this treatise with the following shorthand: for example,

K.9.843.2 refers to Khns Galen edition, (volume 9), page 843, line 2.) I have prepared an English translation

from the Arabic version, included in my dissertation: Glen M. Cooper, Galens Critical Days: Greek

Medicine in Arabic. Edition, translation, and commentary of Hunayn ibn Ishaqs Arabic translation of GalensDe diebus decretoriis; Ph.D. dissertation, Columbia University, 1999.5 In Galen, this idea is not as astrological as it would later become, when the notion of celestial influence was

generalized to embrace all of the planets. For example, in the medieval practice of medicine, this scheme

assisted the physician in knowing when to bleed or test the patients urine.6Prognostic 20.1-16, in Hippocrates.Hippocrates Volume II. Translated by W. H. S. Jones. Edited by G. P.Goold. Vol. 148,Loeb Classical Library. Cambridge: Harvard University Press, 1923. Reprint, 1992, pp.42-43.7Aphorisms 2.23.1-2 and 2.24.1-5, in Hippocrates.Hippocrates Volume IV. Translated by W. H. S. Jones.Edited by G. P. Goold. Vol. 150,Loeb Classical Library. Cambridge: Harvard University Press, 1931. Reprint,1992, pp.112-15.8Epidemics: references to the critical days occur throughout. Books I and III, the most important of all, arefound in:Hippocrates Volume I. Translated by W. H. S. Jones. Edited by G. P. Goold. Vol. 147,Loeb ClassicalLibrary. Cambridge: Harvard University Press, 1923. Reprint, 1984.



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seer have a common heritage. In this article, I will show how Galens method anticipates the

familiar scientific method. In order to achieve this, I must first describe the critical days and

place them in their historical context within ancient Greek medicine.

Anciently, as now, the physician was expected to give a prognosis. The Hippocratic

treatise On Prognosis explained the ideal.9 According to that treatise, prognosis served

several practical purposes. The physician could determine whether a case is hopeless, and if

so, then by refusing to treat the patient he could avoid damaging his reputation. The

physician was expected to infer the present and prior conditions of the patient from direct

observation, without being told. Through a comprehensive prognosis, he could gain the

confidence of the patient, which is extremely important if the patient is to follow the doctors

orders. Furthermore, through subsequent prognoses, the physician could determine whether

the patient has followed his regimen, and thus be exonerated if the prescribed treatment fails.

Clearly, this is a more comprehensive notion of prognosis than the modern understanding.

Prognosis, therefore, was the most dramatic means by which to impress and attract potential

clients, through demonstrating ones knowledge and his power of reason10. In fact, Galen

himself wrote a treatise detailing his most spectacular successes, probably with the intention

of spreading his reputation11.

Prognosis involved reading signs in the patient and comparing them with a prognostic

scheme or theory. The scheme of the critical days was one such theory, central to the

argument of the Prognostic. In a society where exploratory surgery was prohibited,12 the

physician had to rely on external indicators in order to infer the interior condition of the

patients body, to a much greater degree than today. The most conspicuous and useful of

these indicators were bodily effusions, such as urine, excrement, perspiration, etc. By

9 See several articles in: Edelstein, Ludwig.Ancient Medicine: Selected Papers of Ludwig Edelstein. Baltimoreand London: The Johns Hopkins University Press, 1967. Specifically, Hippocratic Prognosis, pp.65-85, and

The Hippocratic Physician, pp.87-131.10 See Barton, Tamsyn S. Power and Knowledge: Astrology, Physiognomics, and Medicine under the RomanEmpire. Ann Arbor, Michigan: The University of Michigan Press, 1994.11 Nutton, Vivian. Galen on Prognosis: Edition, Translation, and Commentary. Berlin: Akademie-Verlag, 1979.12 Cf. The Oath, in Hippocrates.Hippocrates Volume I. Translated by W. H. S. Jones. Edited by G. P. Goold.Vol. 147,Loeb Classical Library. Cambridge: Harvard University Press, 1923. Reprint, 1984, pp. 291-301. Cf.also The Hippocratic Oath: Text, Translation, and Interpretation, in:Edelstein, Ludwig.Ancient Medicine:Selected Papers of Ludwig Edelstein. Baltimore and London: The Johns Hopkins University Press, 1967, pp.3-63.



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themselves, the qualities of the patients excrement or urine were simple facts, devoid of

implications for the outcome of the illness. Nevertheless, within the context of the theory of

the critical days, such facts became prognostic indicators. In his treatise On Crises,13 Galen

describes in detail how specific effusions and their characteristics can be used to infer the

conditions of corresponding regions of the body, i.e. sputum indicates the condition of the

chest and lungs, excrement, of the abdominal cavity, and so forth.

According to Hippocratic medical theory, patients with acute diseases tend to suffer

recurrent dramatic symptoms, called crises,14 which signify an important change in the

illness, toward either better or worse. Health was thought to be a balance of four humors, or

fluids: blood, phlegm, yellow bile, and black bile.15 Certain types of illness were thought to

be caused by a corruption of the humors. Treatment consisted of the physician coaxing the

patients body to cook and expel the noxious humors. This cooking was a kind of

digestion whereby the bodys heat destroys the noxious humor, and it is prepared to be

expelled from the body via one of the effusions already mentioned. The resulting crisis could

be severe and dangerous, and the strain on the body could even kill the patient. The

physician, therefore, who must be skilled in assisting nature in healing,16 must also prepare

the patient to be strong enough to bear the crisis when it comes. It was nature, however,

properly disciplined by skilled medical technique, that effected the actual healing, in the view

of the Hippocratics.

In the best estimation of modern scholars, the regularity of the occurrence of seizures

on critical days suggests that they were the symptoms of cyclical fevers, such as malaria .17

The Mediterranean climate and its seasonal weather patterns are consistent with this

13 The Greek text has been edited by B. Alexanderson: Galenos Peri Kriseon: berlieferung und Text. Vol. 23,Studia Graeca et Latina Gothoburgensia. Gteborg: Elanders Boktryckeri Aktiebolag, 1967. That volumecontains no translation; however, I have an English translation in preparation.14 The Greek term krisis means a judgment: the patient was thought to be judged by the gods, and eithercondemned to die or to be saved.15 Cf. the Hippocratic treatise On the Nature of Man, inHippocrates Volume IV. Translated by W. H. S. Jones.Edited by G. P. Goold. Vol. 150,Loeb Classical Library. Cambridge: Harvard University Press, 1931. Reprint,1992, pp.1-41; and Galen, On the Natural Faculties, Translated by A. J. Brock. Edited by G. P. Goold. Vol. 71,Loeb Classical Library. Cambridge: Harvard University Press, 1916. Reprint, 1991.16 The word physician still preserves a trace of the original conception of the doctor as the ally of nature in

healing. The word for nature in Greek isphysis, and physician isphysikos.17 See Burke, Paul F. Malaria in the Greco-Roman World: A Historical and Epidemiological Survey.Aufstiegund Niedergang der Rmischen WeltII.37.2 (1996): 2252-81.



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hypothesis. There are two variant schemes of critical days in the Hippocratic writings, and

Galen provides a third, although Galens scheme alone is supported by rational argument. A

critical day occurred roughly every fourth day, but the series was counted in an idiosyncratic

manner, to make three weeks fit within twenty days. For example, in counting seven days,

the fourth day is counted twice.18This odd method of counting is justified by noting that the

most prominent critical days, namely the days on which the most crises were thought to

occur, were the seventh, fourteenth, and twentieth days. The intermediate days, i.e. the

fourth, eleventh, and seventeenth days were treated as indicator days. Physicians could use

the condition of the patient on these intermediate indicator days to determine the nature of

the next crisis.

The scheme of the critical days represents the ideal situation, i.e. if the patient and

those who care for him do all that the sage doctor commands. In this case, the crises will fall

on the defined series of critical days. Any departure from the prescribed regimen may cause

the crisis to come prematurely, i.e. before the noxious humors have been completely

concocted, or too late, thus allowing the noxious humors to damage more bodily tissue. The

critical days assisted the physician in this effort by providing a scheme of days on which

crises supposedly occurred most often. The physician could calculate backwards from the

upcoming critical day, and compare what was supposed to happen (according to the scheme)

with the way things were apparently going to happen, based on the patients condition.

Knowledge of the critical day scheme could be part of the physicians esoteric

accoutrements: the patient, without the sophisticated knowledge of an educated physician,

would have no clue how the physician performed the magical prognosis. Galen considered

the critical day scheme important enough to devote two treatises (i.e. On the Crises and On

the Critical Days) to describing the method of diagnosing crises and prognosticating using

18 This method of counting has similarities to the method of counting musical intervals, a convention that

originates with Greek music theorists. This connection is strongly indicated by the fact that the terminology is

identical. I argue elsewhere that Galens theory of the critical days has many affinities with a harmonic

conception of the natural world.



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the critical days.19 Both of these texts were summarized into the ancient equivalent of a

Cliff notes and studied as part of the standard medical curriculum in late antiquity.20

In the steps Galen took to construct his theory of the critical days, we can see a hint of

the later scientific method. Galen states that his theory is based on two components:

experience and reason. These concepts, long since accepted as cornerstones of scientific

method, had never before been so thoroughly and soundly combined as they were in this

treatise. In presenting his theory, Galen shows how to reconcile two major trends in the

development of Greek medicine. Prior to Galen, Greek medicine had been dominated by

either Rationalists or Empiricists. Rationalists insisted that theoretical knowledge was all

that is necessary in treating patients. Empiricists, on the other hand, avoided all theory,

eschewed rational inference except in well-defined situations and of a specific type, and

based their treatments on specific details of each case.21 Galen perspicaciously recognized

that neither reason nor experience alone is sufficient for medicine. His treatises on the

subject are landmarks in the development of scientific thought.22 Yet, his work shows that

the notion of experience had not yet been precisely defined as (controlled) experiment.

To compare Galens method with the modern scientific method as usually

understood, I shall describe what Galen does, and then assess it in light of contemporary

scientific practice. The modern scientific method is generally recognized as having several

stages, involving observation, questioning, formulating hypotheses, and testing them. Greek

thinkers were accomplished at several of these stages, especially observation and formulating

hypotheses. With the requirements that one perform carefully controlled experiments and

that ones results be verified by other researchers, however, Greek science, which was never

standardized nor institutionalized, differs significantly from our own.

19 I am currently preparing editions and translations of the On the Crises and the On the Critical Days in Arabic,and, in the case of the On the Critical Days, in Greek also. These volumes will contain extensive historicalcommentary.20 A. Z. Iskandar, An Attempted Reconstruction of the Late Alexandrian Medical Curriculum,MedicalHistory 20 (1976): 235-58. In late antiquity, the mastery of sixteen medical books summarized in this way wasrequired for the medical degree. These summaries survive only in Arabic.21 A third school developed, the Methodists, who proposed a simpler system of medicine, perhaps in response to

these polar approaches. Galen devotes much polemic and scorn to this group.22 The most important of these treatises are found in: Galen. Three Treatises on the Nature of Science. Trans.Michael Frede and Richard Walzer. Indianapolis: Hackett, 1985. They are: On the Sects for Beginners; AnOutline of Empiricism;and On Medical Experience.



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For convenience of discussion, I have divided Galens procedure into eight steps. I

shall list these steps and then consider each one in the context of Galens discussion of the

critical days.

1) Begin with a question, or set of questions, or an anomaly that calls for an

explanation;

2) Obtain a set of data;

3) Reduce the data to a workable subset;

4) Look for patterns in the (reduced) data;

5) Find correlations with other better-known phenomena;

6) Postulate a causal link between the data and the other phenomena;

7) Exploit the hypothetical connection to infer features of what is to be explained on

the basis of the better-known phenomena;

8) Answer the question: How are anomalies in the data to be accounted for,

according to the new perspective?

In steps 14, Galen employs inductive reasoning, extracting from pure experience as

much as he can. On the basis of observed patterns in the data, he inductively assumed that

the crisis would occur with regularity. These steps occupy most of the treatise, comprising

all of Books I and II. Galen intended these two books to be sufficient instruction in the

method of using the critical days for prognoses for the practical physician who does not

require theory. In steps 58, Galen employs reason to hypothesize causes for the

phenomena. Galen provided this theoretical discussion in Book III, where he invokes

planetary influence to arrive at celestial causes, for the sake of the physician who desires to

understand why the technique works. Each of the above steps will be discussed in view of

material from the On the Critical Days treatise.

1) Begin with a question, an apparent anomaly that stands out, calling for an

explanation.

Galen had three major questions about the critical days from his experience as a

doctor for which he sought answers. The first had dogged him since his youthful medical



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studies: Why is it that three medical weeks come to twenty days and not twenty-one days as

with normal weeks23? He found passages in the Hippocratic writings that suggested that the

critical days cannot be counted in terms of whole days24. The second question: Why does

the crisis occur on some days significantly more often than others do? (It is curious that

Galen looks at the days, not the patient, for the cause.) The third question: Is there a

relationship between the individual critical days; namely, can some days be used as

indicators of later days, thus being useful for prognosis? As a mature physician, Galen wrote

the On the Critical Days treatise to answer these questions, after he had acquired sufficient

medical experience, as well as a mastery of scientific reasoning.

2) Obtain a set of data.

The next step is to obtain a set of data that all agree is valid. In this case, Galen has

chosen to use the Hippocratic data from the Epidemics, since most everyone in his time

agreed that it was canonical. Were he to employ data from his own experience, he might be

accused of fabricating it to support his own theoretical agenda.25 Galen, however, does not

strictly observe this principle, citing his personal experience,26 where he mentions 400

patients whom he observed in one summer to have experienced a crisis on the seventh or

ninth days of their illnesses. In another summer, all of as many patients had the crises on the

fourteenth or twentieth days.27 Still, the basis of his scientific argument is founded on the

Hippocratic datapersonal experience is cited merely for emphasis.

There is a significant difference here between Galens approach and that of modern

science. Modern science would insist on obtaining new data through clinical trial, under

controlled conditions. Historical cases would be considered only as a check on the

experimentally derived theory or hypothesis. Here Galen relies almost completely on the

data of another researcher.

23 Walzer, Richard. Galen on Medical Experience: First Edition of the Arabic Version with English Translationand Notes. Oxford: Oxford, 1947, Chapter 21, p.127 (Frede edition: Three Treatises on the Nature of Science,page 84).24Prognostic 20, ll.1518; pp.42-43, Loeb edition.25 K.842.46 and K.867.151726 K.873.68.27 K.873.810. Note: Galen restricts the data to Epidemics I and III. Books II, IV, and VI he rejects, sincetheir authorship was disputed (K.859.1518), even though he claims that they tend to support his conclusions.



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3) Reduce the data to a workable subset.

The next step is to limit the data, or to reduce it to categories of similar cases. Galen

proceeded systematically through the patients cases described by Hippocrates in Epidemics I

and III, and carefully evaluated the days on which crises were reported. Certain reports of

crises that occurred rarely on a specific day Galen considered anomalous, and discounted

them. He offered an explanation as to why these few data diverge from the main trend, when

he discusses the effects of external environmental factors.28

Galens approach is sophisticated in that he recognizes that unaccountable factors can

upset the natural trend in data. Yet, since he is using anothers data, already at least 500

years old, and not under his control, we are suspicious that he favors his own preconceptions

in selecting the data. Modern science, of course, requires the researcher to define carefully

the experiment, its scope and controls, and to present this along with the data derived from it.

4) Look for patterns in the (reduced) data.

The next step is to examine the reduced data looking for patterns. The Hippocratic

data cluster around specific days, which is to say that crises were observed with greater

frequency in some days, of which the seventh, fourteenth, and twentieth days are the most

prominent. Galens implicit assumption is that, if there were no natural cause at work to

produce this pattern, crises ought to be observed on every day of the illness with similar

frequency, given a large sample of patients. It is hard for us not to see Galens bias toward

these days enter in at this point. He began with the question: Why are the principal critical

days on the seventh, fourteenth, and twentieth days? Now, he finds this very pattern in the

data.

5) Find correlations with other better-known phenomena.

The next step passes beyond simple induction, as Galen begins to seek causes by

correlating the data with other better-known phenomena. In order to win our confidence in

his astronomical knowledge, Galen accurately describes the lunar phases and eclipses as due

to the relative positions of the sun and moon. He shows familiarity with the works of the

astronomer Hipparchus (fl. latter half of 2nd C. BC), from whom he may have derived his

28 1.11.11 (K. 818.1 818.7); 1.11.14-5 (K. 823.17 825.2).



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figures for the lengths of the different kinds of month.29 The popular poet Aratus of Soloi

(c.315240 BC) is also quoted30, to show how the lunar phases can be used to forecast the

weather: farmers and sailors are said to be most familiar with this technique. The moon was

known to exert influence on terrestrial beings. Galen describes how the moon causes the

tides and how its rays cause madness in those who sleep in the open where they are exposed

to them. He suspects that the moon may exert a tidal effect on the fluid humors of the

patients body. Furthermore, Galen noticed a similarity in period between the moon and the

critical days. The moon, he observed, has quarter monthly periods less than seven complete

days. (He considers only the period when the moon is actually visible, which is less than 28

days). When three of these lunar weeks or seasons are summed, one arrives at

approximately twenty solar days. Galen devotes much space to refining the figure, to make it

fit the data even closer. We might accuse him of manipulating the data: it is clear from the

text that he was already convinced by the astrological connection, and wanted to make the

data correlate with it as closely as possible. Such a connection seems more plausible since

all of the phenomena and causes are part of the same system of nature, so the inherent natural

harmony guarantees that there will be a connection. Modern science, of course, has built-in

steps to minimize effects of bias, such as the requirement that the experiments be repeatable

by anyone, no matter what their biases may be.

6) Postulate a causal link between the data and the other phenomena

For Galen, to postulate causal links between entities is the paradigm of how

experience and reason work together in scientific theory. Galen makes the connection

between the lunar motion and the patients illness explicit, through employing analogical

reasoning. We might call what he does scientific modeling. Reasoning by analogy is to take

something that is more familiar, and to use it to explain something similar, but less familiar.

The more familiar entities in this case were the heavens: mostly self-evidently unchanging

and systematic, they seemed to present an excellent causal source for the less-familiar

physiology of cyclical illnesses.

29 K.907.14908.1.30 K.909.313. Translation is found in the Loeb edition, by A. W. Mair and G. R. Mair, Edited by G. P. Goold,

Loeb Classical Library. Cambridge: Harvard University Press, 1969.



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In Book III, Galen presents us with an intricate explanation of why the series of

critical days seems to feature multiples of four and seven days. Since Aristotle, ancient

scientists looked toward the super-lunary heavenly motions for the explanation of cyclical

phenomena in our world. Aristotle had postulated that the suns apparent annual motion

across the sky was the cause of the seasons on Earth generally, and of genesis and demise of

individual beings in particular.31 Galen finds the cause for the regular occurrences of crises

to lie in the moons monthly period, an idea he says he learned from the Egyptians, perhaps

during the time he spent in Egypt as a youth.32 In addition, he probably noticed the fact that

the month is approximately four weeks long, with each lunar season being seven days,

which is also the most significant period of the critical days. Then, remembering the

statement of Hippocrates in the Prognostic that the critical days cannot be counted according

to whole numbers of days, Galen sought a fractional week. Therefore, for three weeks to

sum to 20 days, the medical week must be slightly smaller than a whole seven days.

The period between full moons (approximately 29 1/2 days) is too large for this, since

a quarter of this period is greater than seven days. Accordingly, Galen considers only that

part of this lunar period in which the moon is actually visible, believing that the moons

influence is proportional to the amount of the suns light it reflects at a given time (i.e. the

full moon is more powerful than the crescent moon). That period is, according to Galen,

roughly three days less, or 26 1/2 days. In addition, there is another kind of month, the

sidereal, i.e. the period of the moons motion from a given Zodiac Sign and back again, that

is approximately 27 1/3 days. Galen thinks that these two effects, one due to the lunar

phases, and the other to the moons position along the Zodiac Signs, combine to influence the

patient, but in a mixture that only the gods know.33 He is content, however, to calculate an

average period between the two, to arrive at a medical week of 6 35/48 days. When

31De generatione et corruptione II.11 (338a 19338b 6); English translation is found in: Aristotle. OnSophistical Refutations; On Coming-to-Be and Passing-Away; On the Cosmos. Translated by E. S. Forster andD. J. Furley. Edited by G. P. Goold. Vol. 400,Loeb Classical Library. Cambridge: Harvard University Press,1955. Reprint, 1992, pp.327-29.32 K.911.1418. See Nutton, Vivian. Galen and Egypt. In Sudhoffs Archiv (Beiheft) : Galen und Dashellenistische Erbe Verhandlungen des IV. internationalen Galen-Symposiums Veranstaltet vom Institut frGeschichte der Medizin am Bereich Medizin (Charit) der Humboldt-Universitt zu Berlin 18-20 September1989, edited by J. Kollesch and D. Nickel, 11-31. Berlin, 1993.33 K.932.23.



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multiplied by three, this gives a three-week period of 20 3/16 days, sufficiently close to 20

days for his purpose. Thus, Galen is content that his first two questions have been answered.

He now knows why three medical weeks are about twenty days, and why certain days are

critical and others are not: these facts can be deduced from the features of the moons period.

7) Deduce Features of the Original Subject from the Hypothesis

Once the analogical connection is accepted, Galen feels free to argue in reverse:

because of the parallel between the critical day scheme and the lunar period, and the

postulated causation, specific features of the lunar motion permit him to conclude specific

things about the patients illness. In modern terms, this means to make a fresh deduction

from the tentatively accepted hypothesis. This, by the way, is the basic inference pattern of

astrologers, where precisely we moderns reject astrology: It is one thing to notice the

obvious connection between the solar motion and the changing of the seasons, and the lunar

motion and the tidal cycle (as Galen takes care to note), but it is quite another to push the

analogy farther than warranted and say that specific features of a particular planet or of its

motion have specific earthly effects. Now he has the answer to his third question: individual

days are related to one another by appearing at specific times in the lunar cycle. By knowing

the lunar cycle in detail, he can infer features of the critical days.

8) Account for anomalies in the data

Having derived a scheme that explains the ideal pattern, Galen asks: What causes a

crisis to occur on a non-critical day? And, Why does an expected crisis not occur? In

other words, what factors perturb the scheme? Alternatively, what causes the anomalous

data that he discounted from the Hippocratic data in the earlier stage? Galen does not give

these factors a name, but they were later known as secondary causes, i.e. factors that

interfere with the smooth operation of the primary causes. The primary causes were the

moon and its influence. In Galens discussion, these factors interfere with the smooth

operation of nature, in transmitting the causes and working their effects in the patient. Galen

observed that patients who suffered anxiety or lack of rest did not heal as quickly as others,

or at all. He thus concludes that perturbing factors are whatever upsets or disturbs the

patient. In an ideal situation, if the patient were isolated from external factors that cause him

anxiety and restlessness, such as fire, robbery, torrential thunderstorms and leaky roofs,



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quarreling neighbors and barking dogs,34and furthermore, if he is under the exclusive care of

a physician of Galens caliber, and not being treated by ignorant but well-meaning loved-

ones, then the patients crises will occur according to the perfect scheme of the critical days.

These external factors affect the patient adversely, corrupting the scheme of nature, and

frustrate the healing process. Since the practical effect of such factors is to ruin the

prognosis, and possibly also his reputation, the physician, therefore, is enjoined to avoid,

where possible, any of these deleterious factors, and to minimize the effects thereof.

In conclusion, Galens method has shown sophistication in anticipating parts of later

scientific practice. He was adept at reasoning, and recognizing what constituted a workable

set of data, as well as with deriving a theory. As I mentioned, however, he does not follow a

method of gathering data or experiment that would be considered sound today. Still, his

efforts are an important piece of the puzzle of how science developed into the powerful tool

that it is today, and his neglected treatise ought to be further examined with a view toward

the light it can shed on that question.

Further research into Galens scientific method could follow several paths. The most

compelling might be a comparative study of the scientific method of Galens most famous

contemporary, the Alexandrian astronomer Ptolemy (fl. 2nd C. AD). TheAlmagest35 is a

much larger scale attempt to derive a scientific theory from a collection of astronomical data.

One researcher referred to this process as Saving the Appearances.36 The planetary models

presented there are well known and have been well studied over the past two millennia since

they were first devised. Not long ago a controversial study appeared that called into question

Ptolemys integrity in handling his datain effect accusing him of fabricating data to fit his

theoretical models.37 Research along the line I propose would address those concerns within

a discussion of the honest challenges of reducing a data set to a collection useful for scientific

34 K.825.17826.3.35 Ptolemy. Ptolemys Almagest. Translated by G. J. Toomer. Princeton, NJ: Princeton University Press, 1998.36 See the influential monograph Duhem, Pierre. To Save the Phenomena: An Essay on the Idea of PhysicalTheory from Plato to Galileo. Translated by Edmund Doland and Chaninah Maschler. Chicago: University ofChicago Press, 1969.37 Robert R. Newton, The Crime of Claudius Ptolemy, The Johns Hopkins University Press, Baltimore andLondon, 1977. See the critical review by Kristian Peder Moesgaard inJournal for the History of Astronomy,vol. 11 (1980), pp.133-135.



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modeling. The investigation could also include other ancient theories, such as the same

Ptolemys investigations in musical harmonics,38 in order to be as comprehensive as possible.

Another line of research would be to investigate in detail the debt Galens causal

analysis owes to earlier thinkers, such as Plato and Aristotle. For example, we know that

Galen was an avid student of Plato, since he sought to imitate Platonic arguments, and he

tried to reconcile Platonic and Hippocratic doctrines.39 One could examine the Timaeus,

Platos grand cosmological myth, for any connection it may have with Galens theoretical

scenario.40 Galen wrote a commentary on the Timaeus,41 and that would have to be carefully

examined in light of this question. In the case of Aristotle, one would compare Galens

postulation of celestial causes with Aristotles theory of change as discussed in the Physics.

A study of that scope would be a key to understanding an entire world-view of cyclical

causes, celestial influences, and a purposeful nature. Lastly, one could examine the

influence, if any, the On the Critical Days may have had, either in the Hellenistic, the

Islamic, or the Latin scientific traditions. The precise influence of Galens treatise may have

been obscured by that of PtolemysAlmagest, since the latter was a more studied and more

influential work. One could, nevertheless, examine the medical authors who treat data and

derive theories therefrom. It is known, for example, that medieval physicians employed the

critical day scheme for timing bloodletting or for observing the symptoms of fevers. In

addition, there existed at least one version of the On the Critical Days in Latin,42 and some

medical practitioners possessed tables of planetary ephemerides for use in prognosis.

Although Galens text is only just becoming known once more, much still remains to

be investigated.

38 See Solomon, Jon. Ptolemy Harmonics: Translation and Commentary. Leiden, Boston, Kln: Brill, 2000.See also the following study of theHarmonics: Barker, Andrew. Scientific Method in Ptolemy's Harmonics.Cambridge: Cambridge University Press, 2000.39 de Lacy, Phillip. Galen on the Doctrines of Hippocrates and Plato, 3 volumes. Berlin: Akademie-Verlag,1984.40 For a classic translation and commentary on this influential work, see: Cornford, Francis Macdonald. PlatosCosmology. London: Compton Printing Ltd, 1966.41 Galen,In Platonis Timaeum commentarii fragmenta, ed. H. O. Schrder, Corpus Medicorum Graecorum,Supplementum, vol. 1. Leipzig: Teubner, 1934.42 OBoyle, Cornelius. Medieval prognosis and Astrology: A Working Edition of the Aggregationes de crisi etcreticis diebus with Introduction and English Summary. Cambridge Wellcome Texts and Documents No. 2.Cambridge: 1991.



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Glen M. Cooper

Independent Scholar
