enrnst a. moody-john buridan on the habitability of the earth

Medieval Academy of America

John Buridan on the Habitability of the EarthAuthor(s): Ernest A. MoodySource: Speculum, Vol. 16, No. 4 (Oct., 1941), pp. 415-425Published by: Medieval Academy of AmericaStable URL: http://www.jstor.org/stable/2852841 .Accessed: 09/10/2014 12:48

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact [email protected].

.

Medieval Academy of America is collaborating with JSTOR to digitize, preserve and extend access toSpeculum.

http://www.jstor.org

This content downloaded from 158.251.134.134 on Thu, 9 Oct 2014 12:48:27 PMAll use subject to JSTOR Terms and Conditions

JOHN BURIDAN ON THE HABITABILITY OF THE EARTH BY ERNEST A. MOODY

I. INTRODUCTION PIERRE DUHEM has indicated the importance of the work of John Buridan of Bethune in laying the foundations of the modern science of mechanics. Buridan was the senior member, and the original and constructive genius, of that group of fourteenth-century moderni described by Duhem as 'the Parisian precursors of Galileo.' His ideas in dynamics were given mathematical formulation by Nicholas of Oresme, and were carried to the new universities of central Europe by such distinguished pupils as Marsilius of Inghen and Albert of Saxony. In the sixteenth century, this 'tradition of Buridan' found expositors and defenders in northern Italy, where it exercised a decisive influence on the thought of Leonardo da Vinci and of Galileo.1

Little is known of Buridan's life. He was born at Bethune, near Arras, around 1300 A.D., and was rector of the University of Paris in the year 1328.2 About this time he visited Avignon on some mission to the papal court, pausing en route to take meteorological observations in the Cevennes mountains.3 His name appears in the university archives, and in the Vatican Register, in connection with benefices and honours conferred on him between 1328 and 1358, in the course of a long and distinguished career as teacher on the Faculty of Arts. These documents refer to Buridan as 'the celebrated philosopher,' or as 'our most distinguished man,' and indicate that he was held in high esteem by his colleagues and su- periors.4

Buridan appears to have had only one scholastic enemy: Nicholas of Autre- court, the 'mediaeval Hume.' Nicholas' sceptical ideas are attacked repeatedly in Buridan's writings, and it was Buridan who signed the prohibitory statute of 1340, in which the Faculty of Arts condemned the practice of applying strict logical analysis to scriptural texts, as pursued by Nicholas of Autrecourt and his disciples.5 The last documentary mention of Buridan is dated July 12, 1358, and consists of a concordat between the Picard and English nations, signed by Buri- dan as representative of the Picards.8 It is probable that Buridan's career was

1 P. Duhem, Etudes sur Leonard de Vinci, III' Se'rie: Les pre'curseurs parisiens de Galilee (Paris: A. Hermann et Fils, 1913).

2 Denifle & Chatelain, Chartularium universitatis Parisiensis, ii (Paris, 1891), No. 870. Apparently this document was overlooked by Dr Lynn Thorndike in his History of Magic and Experimental Sci- ence, iII (New York, 1934), p. 374, Note 14, where he states that Duhem and Haureau were mis- taken in saying that Buridan had been rector prior to the year 1340.

3P. Duhem, Le Systeme du Monde, iv (Paris: A. Hermann et Fils, 1916), p. 126. 4Chartul. Univ. Paris, ii, p. 307, Note 1; and Nos 1146, 1156, 1165. See also Denifle & Chatelain,

Auctarium chartularii universitatis Parisiensis, Liber procuratorum nationis Anglicanae, i (Paris, 1894), col. 41.

6 Buridan deals with Nicholas' doctrines in his Quaestiones in octo libros Physicorum Aristotelis, I (edited by John Dullaert, Paris, 1509), Lib. i, Qu. 4, fols 4v-6v, and also in his Quaestiones in Meta- physicam Aristotelis (edited by J. Badius, Paris, 1518), Lib. ii, Qu. 1, fol. Ixr.

6 Auctarium chartul. univ. Paris., i, cols. 206, 212, and 233-235.

415


416 The Habitability of the Earth

terminated in that year by death from the plague, for his name ceased thence- forth to occur in the university records.

The extant writings attributed to Buridan consist almost exclusively of Ex- positions and Questions on the treatises of Aristotle. In this field he was ex- tremely prolific, his lectures covering the entire corpus of authentic aristotelian writings, with the exception of the works on animals and the Poetics. These lectures follow the order and subject matter of the aristotelian treatises, but those which are in the form of Questions are very independent of the text, and are equivalent in most cases to original treatises.1

It was in the field of physics, and particularly in dynamics, that Buridan's thought was most original, constructive, and influential. This fact was empha- sized by Duhem, who rated Buridan a mediocre astronomer, and credited Oresme and Albert of Saxony with the theories and discoveries which mark the beginnings of modern kinematics and statics. A more careful examination of fourteenth-century scientific writings shows, however, that most of the ideas advanced by Oresme and Albert in these fields were derived from Buridan, wlho in turn seems to have borrowed them from earlier fourteenth-century teachers at Oxford and Paris. The whole question of Buridan's originality, and of the significance and coherence of his work in physical science, requires for its determina- tion a much greater knowledge of fourteenth century scientific writings, and a more exhaustive study of Buridan's own works, than has yet been achieved.2

Quite apart from the question of originality or genius, however, Buridan's writings have great historical value and interest. For one thing, they cover practically the whole field of scientific and philosophical knowledge and opinion, of the fourteenth century, and thus form a kind of Summa philosophiae for that period. Their method of discussion, furthermore, gives them particular value as sources of information concerning the state of fourteenth-century scientific knowledge as a whole. In his capacity as teacher, Buridan takes it upon himself to set forth all the diverse views and arguments of his contemporaries on each problem, and in many instances he confines himself to such exposition, leaving it to the auditor or reader to make his choice among the alternative positions. Such is the case in his treatment of the problem of the rotation of the earth on its own axis, given in Question 22 of the second book of his Quaestiones super libris de caelo et mundo. In this Question, Buridan expounds the theory of diurnal rotation which Copernicus was to defend more than one hundred and fifty years later, giving excellent arguments in its favor. He then argues against the theory from the standpoint of the

' B. Geyer, Ueberwegs Grundriss der Geschichte der Philosophie, Band II (1lth edition, Berlin, 1928), p. 595, gives the list of printed editions. The manuscript texts are discussed by K. Michalski, 'Les courants critiques et sceptiques dans la philosophie du XIVe siecle,' in Bulletin International de l'Acade'mie Polonaise des Sciences et des Lettres, Classe d'Histoire et de Philosophie, Annee 1925 (Cracow: Imprimerie de l'Universite, 1927), pp. 202-209.

2 P. Duhem, Le Systeme du Monde, iv, pp. 135-142, discusses Buridan's astronomy. On the ideas in statics advanced by Albert of Saxony, see P. Duhem, Les Origines de la Statique, ii (Paris: A. Her- mann et Fils, 1906), ch. xv. On Oresme, see P. Duhem, Etudes sur Leonard de Vinci, I1e Sgrie (Paris, 1913), pp. 346-398, and E. Borchert, 'Die Lehre von der Bewegung bei Nicolaus Oresme,' in Beitrdge zur Geschichte der Philosophie des Mittelalters, Band xxxi, Hft. 3 (Muenster, 1934).


The Habitability of the Earth 417

Ptolemaic astronomy, and indicates his own preference for the latter system. But he clearly points out to his students that the newer theory is entirely defensible, since the observed movements of the heavenly bodies may be described in func- tion of one hypothesis as well as of the other.1

The text here edited, dealing with the problem of the habitability of the earth, is based on two manuscripts of Buridan's Quaestiones super libris de caelo et mundo, where it appears as the seventh Question of the second book. The two manuscripts utilized for this edition are from the Bavarian State Library at Munich (Cod. lat. monac. 19551), and from the library of Bruges (Ms. 477, anon.). The correspondence of the Questions on the De caelo, contained in the anonymous Bruges manuscript, with those attributed by the Munich manuscript to John Buridan, was discovered by the Abbe Michalski. Since the only copies of this work previously known were those offered by two manuscripts at Munich, and since the Bruges text is more complete and more legible than that of the Cod. lat. monac. 19551, Michalski's identification is of great value.2

The Munich Codex 19551 contains 149 folios, closely written in Gothic cursive of the late fourteenth century. The colophon to Buridan's Questions on the De generatione et corruptione, on fol. 125v, gives 1378 as the date of the copy; and since the handwriting of this text appears to be the same as that of the copy of Buridan's Questions on the De caelo et mundo immediately preceding, we may conclude that both works were transcribed in this manuscript around the year 1378. The Questions on the De caelo et mundo cover folios 7Or-105v, and consist of twenty-five Questions on Book i of Aristotle's treatise, twenty-three on Book ii, two on Book iII, and eight on Book iv. The colophon, at the foot of the second column on folio 105v, attributes the text directly to Buridan, as follows: "Expli- ciunt quaestiones super libris de caelo et mundo Magistri Johannis Buridani Rectoris Parisius.'

Other works of Buridan are also contained in this Munich codex: an abbre- viated version of his Questions on Aristotle's Physics, a set of his Questions on the De generatione et corruptione, and an incomplete set of his Questions on Aristotle's Parva naturalia. While Duhem, on the basis of an inaccurate report of the manuscript transmitted to him by Pere Bulliot, asserted that these texts were reportata

1 J. Buridan, Questiones de caelo et mundo, ii, Qu. 22 (Cod. lat. monac. 19551, fol. 99r): 'Et in- dubitanter verum est quod si esset ita sicut ista opinio ponit, omnia in caelo apparerent nobis sicut nune apparent.' This Question was edited by J. Bulliot, 'Jean Buridan et le mouvement de la terre, Question 92e du second livre du "De Coelo",' in Revue de Philosophie, 14e annee, t. xxv (Paris, 1914). Bulliot's text is that of the Munich Ms 19551.

2 K. Michalski, 'La physique nouvelle et les differents courants philosophiques au XIVe siecle,' Bulletin International de l'Academie Polonaise des Sciences et des Lettres, Classe d'Histoire et de Phi- losophie, Avril-Juin 19Q7 (Cracovie: Imprimerie de l'Universite, 1928), pp. 114-117. Not having had the opportunity to examine the Cod. lat. monac. 19551, or Bruges 477, directly, I have followed the careful report on them given by Michalski in the above monograph; my edition of the text is based on photo- static copies of the folios containing Buridan's Qu. de caelo et mundo. I have to thank the director of the Bayerische Staatsbibliothek for his courtesy in arranging for the taking of photostats of the cod. lat. monac. 19551, fols. 70r-125v, in my behalf. The other Munich manuscript, purporting to contain a copy of this work of Buridan, is Cod. lat. monac. 761; due to war conditions, I have been unable to obtain either a photographic reproduction of this manuscript, or a description of its contents.



rather than literal copies of Buridan's lectures, Michalski concludes, after careful examination and comparison of extant manuscript copies, that the Munich text of the Questiones de caelo et mundo is to be attributed to Buridan.1

The Questiones de caelo et mundo contained in the anonymous Bruges Ms 477 commence on fol. 164v and end on fol. 21Or, followed by a table of the Questions, covering fols 21Or-210v. The Questions contained in this text are identical with those of the Munich codex, except that it contains an initial Question (Utrum de mundo debet esse scientia distincta a scientia libri Physicorum) which is missing from the Munich manuscript. The Bruges copy is in all respects superior to that of Munich; it is more carefully transcribed, more free from lacunae, and more legible. Though on palaeographic grounds it is not to be considered earlier than the Munich codex, but probably slightly later, its relatively greater completeness indicates that it is either a more faithful copy of a common original, or a copy of a more accurate earlier text. The two manuscript copies are unquestionably of common ancestry, the variants being quite obviously due to the copyists. In almost all instances it is the scribe of the Munich codex who is at fault, by reason of haste, inattention, or lack of comprehension of the work being copied.

The seventh Question on the second book of Aristotle's De caelo, in which Buridan discusses the problem of whether the whole earth is habitable, is here edited for the first time from the two manuscripts above mentioned. In Cod. lat. monac. 19551, this Question extends from fol. 87r, col. A to fol. 88r col. B; in the Ms. Bruges 477 it runs from fol. 188v col. A to fol. 189v col. B.

The problem of the habitability of the earth, treated in this Question, was not new in the mediaeval tradition. The geographical information and misinforma- tion contained in Pliny's Naturalis Historia was known to mediaeval writers, and utilized to some extent in their discussions. But their interest in the problem, and their methods of seeking its solution, were inspired by Aristotle rather than by Pliny; they were concerned with the causes which determine and limit the possibilities of human habitation of the earth, rather than with the mere facts as to how much of the earth is actually inhabited. Hence little attention is paid to the descriptive information provided by explorers and travellers, except insofar as it may confirm the theoretical grounds. The discussion is pursued in terms of astronomy and geology, sciences which underlie geography by exhibiting certain general causes which limit geographical possibilities. It is because the principles of the solution of the problem are astronomical and geological, that Buridan raises the question of the earth's habitability in his lectures on the De caelo et mundo.2

Buridan's discussion falls into two main divisions: he first treats of climatic conditions determined by astronomical causes, as factors limiting the habitability

I Michalski, 'La physique nouvelle, etc.,' loc. cit., pp. 115-116. 2 The aristotelian text of the De caelo does not directly raise this question at all, though the dis-

cussion in Book ii, ch. 4, fols. 287a 32-287b 21, of the sphericity of the earth and of the regions of the four elements, is relevant to the problem, as Buridan's discussion shows. The traditional locus of this problem of the habitability of the earth was Aristotle's Meteorologica, ii, ch. 5, 362a 33-362b 29, where climates and winds are discussed. Thus Aquinas' treatment of the problem is found in his Expositio in Meteorologicam Aristotelis, ii, Lect. x (Leonine ed., iii, pp. 419-420), and not in his commentary on the De caelo.



of the earth, and he then deals with the problem of why the dry land has not long since been washed into the sea. The discussion of climates involves the traditional distinction of the five zones, and is chiefly devoted to the problem of whether or not the equatorial zone, and the south temperate zone, are fitted for human habitation. Most of the arguments invoked are purely astronomical, but the Arab philosopher Ibn-Sina (Avicenna) is cited as authority for the theory that the most temperate of all climates is found at the equator, and for a story that some men had penetrated to this region and had brought back reports of a great civilization there, possessed of all the perfections of an earthly paradise. Buridan's attitude toward this tale of Avicenna, and toward the Arab philosopher's a priori arguments in support of it, is reserved if not indeed sceptical.'

More interesting, from the scientific point of view, is the discussion given in the second part of the Question. Since water is lighter than earth, and since the elements tend toward equilibrium at their proper levels, it would seem that the whole earth should be covered by water. This theory is confirmed by the observed phenomenon of erosion, indicating that over a long period of time the dry land should have been completely washed into the sea by the action of rivers and rain. Since this has obviously not happened, there must be some constant process which counterbalances erosion, by which the elevation of the continental areas above sea level is maintained.

Two theories are suggested. The first rests on the postulate that the sphere of water is eccentric to the earth, so that its natural center is outside the center of the earth. Several objections are raised against this view, which seems to Buridan insufficient because of its failure to give any natural cause of such eccentricity. He therefore offers another 'more probable' theory, based on the distinction between center of gravity and center of magnitude. If we assume a common center of gravity for both earth and water, the water will always flow to its natural level with respect to this center, and since it is a fluid its center of magnitude will always be practically coincident with its center of gravity. But the center of magnitude of the earth need not coincide with its center of gravity, because earth is not a homogeneous fluid like water. On the contrary, the continental areas, which are exposed to the heat of the sun and to pulverization and admixture of air, will be lighter and less dense than those parts of the earth which are under the sea. Since, therefore, the earth is not strictly symmetrical but has more dry land on one side than on the other, it cannot become symmetrical in this respect, because its center of gravity cannot become coincident with its center of volume. The processes of erosion tend to make the dry side of the earth smaller in relative volume; but in so doing they make it lighter, and thus offset the change effected in the earth's center of volume, by an equal change in its center of gravity.

1 This theory of Avicenna is twice mentioned by Roger Bacon, in the Opus maius (ed. J. H. Bridges, Oxford 1897-1900), Part iv, Dist. iv, ch. 4, and in the Oputs tertium (ed. J. S. Brewer, London 1859), pp. 119-120. Bacon cites as sources the first book of Avicenna's Canon, and the first book of his treatise on animals. I have been unable to locate this second citation in the Venice, 1530, edition of Avicenna; the first refers to the Canon, Lib. I, Fen ii, Doctrina ii, cap. 8 (Avicennae medicorum arabum principis Liber Canonis. . . Basileae, per loannes Hervagios, 1556, pp. 62-63).



This theory, which seems to please Buridan greatly, affords an explanation of a number of phenomena. Besides accounting for the continued existence of dry land despite long continued erosive processes, it affords an explanation for the forma- tion of mountains, replacing the numerous fantastic theories advanced by ancient writers. It likewise explains the presence of fossils in regions far from the sea, and offers a basis for a mechanical explanation of earthquakes. Possibly Buridan was aware of these applications of his theory, for fossils and earthquakes were observed and discussed in mediaeval times. Leonardo da Vinci, in any case, made the application to the problem of fossils, having become acquainted with Buri- dan's theory of the movement of the earth by way of Albert of Saxony.'

The significance of Buridan's discussion and resolution of this problem of land and sea lies in the fact that he sought, and found, a strictly mechanical explanation of a geological problem. Tbis explanation was, in essentials, the theory of isostasy which plays such a basic part in modern physical geology. Whether the theory was original with Buridan, or taken by him from some unidentified pred- decessor or contemporary, is a matter of conjecture. Dr Lynn Thorndike has found a full statement of the theory in an anonymous treatise on natural phi- losophy written in the fourteenth century; but the content of this treatise, as described by Dr Thorndike, indicates that it was written in the latter part of the century, and probably after Buridan's death.2

It is interesting to compare Buridan's discussion concerning the habitability of the earth with that which St Thomas Aquinas offers on the same topic in his commentary on the Meteorologica of Aristotle.' St Thomas is content to restate Aristotle's conclusions and arguments as they stand, without seeking to develop the problem further. Buridan, by contrast, takes the aristotelian text as a point of departure for independent inquiry - an inquiry primarily determined by mechanical principles in relation to observable phenomena. Arguments of a teleo- logical and analogical order, though taken into consideration, no longer figure as 'demonstrations,' but only as 'persuasions.' Physical explanation is conceived in terms of forces, resistances, and measurable or observable factors.

Is this fourteenth-century shift from a 'metaphysical' to a 'scientific' attitude toward cosmological problems a sign of the failure of the mediaeval philosophical enterprise, or of its success? This is a question worthy of our most considered reflection.

1 P. Duhem, Etudes sur Leonard de Vinci, IlIf Serie, pp. 32-33. 2 L. Thorndike, History of Magic and Experimental Science, III, pp. 580-581. Many of the theories

advanced in this treatise, as described by Dr Thorndike, are characteristic of Buridan himself. It cannot be a work of Buridan, however, since its author opposes Buridan, and defends Ockham's position, on the fundamental problem of whether or not motion is an absolute entity distinct from the mobile quod movetur. Buridan's theory of the center of gravity of the earth, in connection with the maintenance of dry land above sea level, was also stated by John de Fundis in 1435, according to Dr Thorndike, op. cit., iv, p. Q39.

3 Thomas Aquinas, Expositio in Meteorologicam Aristotelis, ii, Lect. x (Leonine ed., iii, pp. 419- 420).



II. TEXT (JOHANNIs BURIDANI SUPER LIBRO SECUNDO DE CAELO ET MUNDO

QUAESTIO SEPTIMA)

Septimo consequenter quaeritur: Utrum tota terra sit habitabilis. 1

Arguitur primo quod sic, quia communiter dicitur quod una quarta pars terrae est habitabilis, et non apparet ratio quare magis debeat esse una quarta habitabilis quam aliae quartae; igitur omnes quartae debent concedi habitabiles, et per consequens tota terra. Et 5 hoc etiam apparet per concessionem Aristotelis, qui concedit ita esse habitabilem terram nobis oppositam sicut istam; de illis enim dicit quod ipsi habitant sursum et ad dextram, nos autem deorsum et ad sinistram.'

Deinde arguitur quod nulla pars terrae debeat esse habitabilis, quia terra est sphaerica 10 et in medio mundi sicut centrum, ut habetur secundo huius.2 Aqua autem naturaliter sita est supra terram et fluit semper ad locum decliviorem, propter quod etiam naturaliter efficitur sphaerica, ut habetur secundo huius ;3 ex quo sequitur quod ipsa naturaliter debet totam terram circumdare, et sic nulla pars terrae esset habitabilis propter aquas. Nec valet dicere quod sunt montes et elevationes in terra, ad quas elevationes aqua circumdans 15 non attingit, ideo illae elevationes sunt habitabiles. Contra hoc obicitur fortiter, si mundus fuerit perpetuus ut ponit Aristoteles, quia omni tempore partes superiores ex montibus descendunt multae ad valles, et nullae vel paucae ascendunt; et sic ab infinito tempore illi montes deberent esse totaliter consumpti et reducti ad planitiem.

90 Similiter, si terra sit elevatior ubi non est mare, et depressior ubi est mare seu declivior,

tunc manifestum est quod omni tempore multae partes istius terrae altioris portantur cum fluviis in profundum maris, unde provenit quod mare efficitur grossum et salsum; et illae partes terrae non revertuntur de profundo maris ad istam terram, imo quod elevatur de mari per exhalationem seu evaporationem non est nisi subtile aquosum, et non grossum 25 terrenum. Ideo videtur quod ab infinito tempore tota profunditas maris deberet esse re- pleta terra, et haec elevatio terrae deberet esse consumpta; et sic aqua naturaliter deberet totam terram circumdare, nec deberent esse aliquae elevationes discoopertae.

Et hoc etiam confirmatur ex alio, quia sicut sphaera aeris valde excedit in magnitudine 30 et profunditate sphaeram aquae, ita, ut sit proportio elementorum, sphaera aquae debet notabiliter excedere in magnitudine et profunditate sphaeram terrae; et si sit ita, ipsa debet elevari undique super terram plus quam ad montes altissimos; ideo nihil debet re- manere habitabile.

5 Oppositum amborum apparet ad sensum. Magna enim pars terrae habitatur, et magna

etiam est quae non habitatur.

Ista quaestio videtur mihi valde difficilis. Et primitus notandum est de ea, quod dupli- 39

Varia lectio: [B= Ms. Bruges 477: M= Cod. lat. Monac. 19551) 1. Septimo om. B. S. pars om. B. 4-5. aliae quartael alia 31. 14. esset] est M. 19. totaliter] toti B. 24. quod om. M. R5. seu] vel M. 30. etiam om. 31. 31. debet] deberet M. 36. habitatur] inhabitatur M. 39. valde om. M. primitus ... ea] primo notandum M.

1 Aristotle, De caelo, ii, ch. 2, 985b 23-5. 2 Aristotle, De caelo, ii, ch. 14, 296b 7-298a 20. t Aristotle, De caelo, ii, ch. 4, Q87b 5-8.



1 citer terra potest reddi inhabitabilis: uno modo propter excessum in primis qualitatibus, maxime in calido et in frigido; alio modo propter impedimentum aquarum. Et primo dicemus de primo istorum modorum.

5 Notandum est ergo quod terra imaginatur dividi in quinque zonas secundum exigentiam corporum caelestium. Prima zona est sub circulo aequinoctiali inter tropicum Cancri et tropicum Capricorni, et directe super illam zonam decurrunt omni tempore sol et alii planetae. Et de ista zona dicunt multi quod ipsa est inhabitabilis propter excessivum calorem ab ipso sole.'

10 Aliae duae zonae sunt sub polis, ita quod una est sub arctico, alia sub antarctico; et extendunt se usque ad illos parvos circulos quos circa polos mundi describunt poli zodiaci moti motu diurno. Et dicitur quod illae duae zonae sunt inhabitabiles ex nimio frigore propter elongationem a sole.2

Aliae duae zonae sunt una inter tropicum Cancri et parvum circulum arcticum, in qua i5 habitamus; alia similiter est ad aliam partem inter tropicum Capricorni et parvum circu-

lum antarcticum. Et istae duae reputantur communiter habitabiles et satis temperatae, quia nec sunt sub sole nec nimis distant a sole.3

Ita dicunt multi communiter quantum est ex caliditate et frigiditate; et omnes, ut mihi videtur, concesserunt quod duae zonae sub polis sunt inhabitabiles vel nimis difficilis

Ro habitationis propter nimium excessum frigoris et recessum earum a sole. Omnes etiam concesserunt zonam inter tropicum Cancri et parvum circulum arcticum esse habitabilem, quia experimur eius habitationem. Sed de aliis duabus zonis fuerunt diversae magnae opiniones.

25 Et modo dicemus de zona media quae est inter tropicos sub aequinoctiali. Statim enim prima facie apparet quod illa propter nimium calorem sit inhabitabilis, quia procedentes usque ad tropicum Cancri inveniunt tantum calorem, quod ibi homines ultra communem modum hominum aduruntur et fiunt nigri, sicut apparet de Indis et Aethiopibus; ideo videtur quod ultra esset tanta caliditas quod non possent ibi homines habitare. Et hoc con-

s0 firmatur, quia si esset ultra habitatio, aliqui nostrum venissent ad eos, vel illi venissent ad nos; quod non est auditum, ut aliqui dicunt.

Tamen hoc non obstante Avicenna4 opinabatur contrarium, dicens quod sub aequinoctiali erat summe bona et temperatissima habitatio; et dicebat se audivisse quod aliqui venerunt ad illum locum qui reversi erant et narrabant de una maxima et nobilissima

35 civitate quae erat sub circulo aequinoctiali. Et Avicenna habet plures rationes per se. Prima est, quod semper illic sunt dies aequales noctibus, et ideo frigiditas noctis tem-

perat calorem diei et e contrario. Secunda ratio est, quod licet sol transeat directe super capita eorum, tamen statim

transit et non multo tempore manet ibi. In sphaeris autem declivibus dies sunt valde longi 40 et sol, licet non directe veniat super capita hominum, tamen venit prope et non cito

transit, imo longo tempore girat circa capita hominum. Et ideo non oportet quod sub

5. est ergo] igitur M. I. describunt om. M. 12. moti] in M. 14. Cancri om. B. 18. multi om. M. 20. etiam] autem M. 25. enim om. M. 26. sit] est M. 30. aliqui ... venissent] aliquis vestrum venisset B. 33. dicebat] dixit M. 34. venerunt] fuerunt B. 34. qui . . . erant om. B. et nobilissima om. M. 38. est om. Ml. 38. tamen] cum B. 41. longo tempore] longe B.

I Cf. Aristotle, Meteorologica ii, ch. 5, 362b 5-8. 2 Cf. Aristotle, Meteorologica ii, ch. 5, 362b 8-9. 3 Ibid., 362b 5. 4 Avicennae medicorum arabum principis Liber Canonis, de medicinis cordialibus, et Cantica.

Basileae, per loannes Hervagios, 1556, Lib. i, Fen ii, Doctrina ii, cap. 8 (pp. 62-63). Cf. Roger Bacon, Opus maius, Part iv, Dist. iv, cap. 4 (ed. J. H. Bridges, Ox. 1897-1900), and Opus tertium (ed. J. S. Brewer, London 1859), pp. 119-120, who also cites Avicenna's first book on animals as source of this opinion.



aequinoctiali sit tanta caliditas quanta est hie aliquando in aestate, nec unquam est ibi 1 intensa frigiditas; ideo locus est ibi temperatissimus.

Tertia ratio est, quia supponimus caelum et astra esse perfectissime ordinata ad guber- nandum istum mundum, et maxime homines et animalia et plantas, de quibus natura propter eorum nobilitatem debet esse maxime sollicita; ideo rationabile est quod ad illum 5 locum sit perfectissima hominum habitatio ad quem omnes stellae caeli ordinatae sunt et simul habent aspectum; sed hoe est ad locum sub aequinoctiali. Illis enim omnes stellae oriuntur et occidunt, nobis autem nunquam oriuntur stellae quae sunt iuxta polum antareticum; ergo illic debet esse summe bona habitatio. Unde Avicenna sub aequinoctiali dicit esse paradisum terrestrem in quo semper omni tempore plantae frondent et florent et 10 fructificant, et omni tempore blada matura colliguntur et alia seminantur.

Sicut dubitatum est de zona media, ita aliqui dubitant de illa zona quae est inter tropicum Capricorni et parvum eirculum antareticum. Dicunt enim aliqui quod licet ista zona quam habitamus sit temperata et habitabilis, tamen non sequitur quod illa alia zona sit 15 temperata vel habitabilis, propter unam imaginationem de sole. Astrologi enim ponunt solem habere eceentricum, et ita sol multo remotior est a terra quando est in auge eceen- trici, et est multo propinquior terrae quando est in opposito augis. Modo agens naturale, quanto est propinquius passo, tanto fortius agit in ipsum; et quanto est remotius a passo, tanto debilius agit in ipsum. Modo ultra dicunt isti quod in Cancro sol est in auge eccen- 20 trici, et in Capricorno est in opposito augis; et ideo sequitur quod ista zona nostra efficitur temperatior quia in aestate, sole existente in Cancro et quasi supra nos, sol est valde remotus a terra, propter quod calor est minus intensus. Sed in hieme, sole existente in Capri- corno, fit nobis frigiditas quia sol est nobis valde obliquus; tamen quia sol tune est propinquus terrae non fit nobis tanta frigiditas sicut si esset remotus. E contrario autem est de 25 illa alia zona quae est ultra tropicum Capricorni; quia cum sol est in Capricorno ipse est quasi supra capita eorum, et cum hoc est propinquus terrae; ideo nimis intense calefacit, et non potest habitari vel male potest habitari illa regio propter nimium calorem. Sed quando sol est in Cancro, tune est illis valde obliquus, et cum hoc est multum a terra remotus; ideo valde modicam virtutem habet super illos, ideo efficitur ibi frigiditas nimis 30 intensa et prohibens bonam habitationem.

Nunc restat dicere de inhabitatione propter aquas. Et sunt de hoc tres magnae opiniones. Aliqui ponunt unam solam quartam vel quasi habitabilem, et alii ponunt omnes quartas terrae habere habitationes. Et de ista opinione erit primo dicendum. 85

Isti ergo dicunt tam terram quam aquam esse concentricas mundo, ita quod centrum mundi sit centrum earum ambarum; tamen dicunt in qualibet quarta terrae esse multas plagas discoopertas aquis, propter multas terrae gibbositates et quasi montium elevationes eminentes super aquas. Et dicunt multas alias partes terrae esse coopertas aquis propter earum depressiones, ad modum vallium inter praedictas elevationes. Et hoc dicunt 40 ita esse in qualibet quarta terrae, cuius signum est quod de una plaga valde magna discooperta nos pertransimus valde magnum et longumn mare et venimus ad aliam plagam discoopertam valde magnam, et verisimile est quod ita esset circumeundo terram totam.

Sed contra istam opinionem sunt duae magnae dubitationes. Prima est, quia omnia maria quae ab aliquibus poterunt transiri, et omnes terrae habitabiles quae poterunt in- 45 veniri, continentur in ista quarta terrae quam habitamus. Et aliqui laboraverunt in mari ad permeandum mare in aliis quartis, et nunquam potuerunt pervenire ad aliquam terram 47

6-7. ordinatae ... habent] habent ordinate et simul B. 10. semper om. M. 14. quod omn. B. 18. terrae om. M. 21. ideo] tunc B. 22. et ... nos] est quasi nos supra B. valde om. B. 28. habitari] inhabitari M. 34-35. omnes ... habitationes] habere alias quartas M. 37. ambarum om. B., add. in marg. M. 39. coopertas] discoopertas M. 43. esset] accideret M. 47. terram] partem M.



1 habitabilem; et ideo dicitur quod Hercules in finibus huius quartae infixit columnas, in signum quod ultra eas non erat terra habitabilis nec mare permeabile.

Alia dubitatio difficilior est, quae dicta fuerit prius, quia haec opinio non potest salvare, si mundus fuerit aeternus, quo modo istae elevationes terrae possunt salvari ab aeterno,

5 cum semper ex eis fluant multae partes terrae cum fluviis ad fundum maris. lam enim ab infinito tempore deberent tales fundi marium esse repleti, et deberent elevationes terrarum esse consumptae; quod non est conveniens dicere volentibus tenere perpetuitatem mundi in statu prospero animalibus et plantis sicut nunc est.

Ideo alia fuit opinio, quae ponebat quod ad salutem animalium et plantarum Deus et 10 natura ab aeterno ordinaverunt aquam eccentricam, ita quod centrum terrae sit centrum

mundi, sed centrum aquae sit extra centrum mundi. Et sic dicunt aquam semper defluere ad locum decliviorem non respectu centri terrae vel mundi sed respectu proprii centri aquae. Et sic potest esse una pars terrae quasi quarta discooperta aquis, omnibus aliis existentibus coopertis aquis. Et sic isti salvant quod non sit nisi una quarta terrae, vel

15 quasi, discooperta et habitabilis. Sed contra istam opinionem remanent iterum duae dubitationes. Prima est, quia iste

mundus regitur a Deo, sed tamen mediante caelo si volumus loqui naturaliter. Et ideo ex parte caeli oportet assignare causam illius eccentricitatis. Non enim posset bene assignari ex parte terrae, cuius partes sunt consimiles et homogeniae; nec etiam ex parte aquae cum

0 eius partes sint etiam consimiles et homogeniae; nec ex parte caeli moti, quia illud indif- ferenter et undique volvitur circa terram et circa aquam, ideo ex parte ipsius non potest poni ratio quare centrum aquae esset extra centrum terrae magis ad unam partem quam ad aliam.

Secunda dubitatio est, quo modo montes sic possent infinito tempore salvari, cum 25 omni tempore multae partes de locis altioribus descendant ad loca inferiora, et paucae

ascendant vel portentur de locis bassis ad loca alta, maxime si velimus loqui de valde altis montibus; ideo in infinito tempore illi montes alti deberent esse consumpti.

Propter hoc est tertia opinio, quae videtur mihi probabilis, et per quam perpetuo sal- varentur omnia apparentia, ponendo quod tam terra quam aqua sunt concentricae mundo,

30 ita quod tota terra est innata congregari circa centrum mundi, et etiam omnis aqua est innata fluere ad locum decliviorem respectu centri mundi. Sed multa aqua est in visceribus terrae, et multa etiam est commixta aeri per evaporationes; ideo non oportet tantam aquam esse in mari quod excedat elevationes terrae.

Sed tunc quaeritur quo modo aeternaliter salvabuntur illae elevationes terrae. Re- 35 spondetur, si secundum Aristotelem poneretur mundus aeternus, quod ab aeterno ad salu-

tem animalium et plantarum mundus est ordinatus quod una pars terrae, quasi una quarta, est discooperta aquis et eminens super aquas; et semper manet et manebit etiam naturaliter discooperta, non obstante concentricitate et licet etiam circumscriberemus montes.

Et est talis imaginatio, quod terra in parte discooperta alteratur ab aere et a calore solis, 40 et commiscetur sibi multus aer, et sic fit illa terra rarior et levior et habens multos poros

repletos aere vel corporibus subtilibus; pars autem terrae cooperta aquis non sic alteratur ab aere et sole, ideo remanet densior et gravior. Et ideo qui divideret terram (1. si dividere- tur terra) per medium suae magnitudinis, una pars esset valde gravior quam alia, illa enim

44 pars in qua terra esset discooperta esset multo levior. Et sic apparet quod aliud est cen-

1. infixit] fixit M. 2. erat] esset M. 3. fuerit] fuit M. salvare] salvari B. 4. ab aeterno] ex terra M. 9. salutem] saltum M. 19. non] in M. sed] sed non M. 13. quarta] esse add. B. 14. terrae om. M. 15. et] etiam M. 16. opinionem om. M. quia] quod M. 19-20. cum ... homogeniae] propter eandem rationem M. 20. illud] non M. 24. est om. M. ?6. vel ... alta] e contrario M. ?7. in om. M. 29. quod] quoddam M. 31. fluere] defluere M. 41. repletos ... subtilibus] corporibus subtilibus vel ipso aere M. 4e. terram om. M. 44. qua terra] aqua Ml. discooperta] illa autem add. M.



trum magnitudinis terrae, et aliud est centrum gravitatis eius; nam centrum gravitatis I est ubi tanta est gravitas ex una parte sicut ex altera, et hoc non est in medio magnitudinis ut dictum est. Modo ultra, quia terra per suam gravitatem tendit ad medium mundi, ideo centrum gravitatis terrae est medium mundi, et non centrum suae magnitudinis, propter quod terra ex una parte est elevata supra aquam et ex alia parte est tota sub aqua. 5

Sed tune cum quaeris ultra, cum partes illius terrae elevatae fluant cum fluviis ad aliam partem ad fundum maris, quo modo potest salvari ista elevatio; respondetur quod si multae partes terrae elevatae moventur ad aliam partem ad fundum maris, tune gravificant illam partem ad quam fluunt, et tune semper in residuum quod manet discoopertum agunt sol et aer, et reddunt illam partem leviorem, et ita illa pars quae prius erat centrum 10 gravitatis non amplius erit centrum gravitatis. Ideo oportet quod totalis terra moveatur et elevetur versus plagam discoopertam; et tune ex hoc sequitur ultra, per processum tem- poris, quod partes quae sunt in centro terrae tandem venient ad superficiem terrae habitabilis, propter hoc quod continue removentur de ista terra partes quae fluunt ad partem oppositam; et sic semper salvatur elevatio terrae. 15

Sic etiam salvatur generatio altissimorum montium, quia intra terram sunt partes terrae bene dissimiles, prout experiuntur fodientes; aliquae sunt lapidosae et durae, aliae sunt magis tenerae et citius divisibiles. Cum ergo illae partes interiores terrae elevantur modo praedicto ad superficiem terrae, illae quae sunt tenerae et divisibiles per ventos et pluvias et fluvios, iterum inoventur ad profundum maris; aliae autem magis durae et 90 lapidosae non possunt sic dividi et fluere, ideo manent et continue per longissima tem- pora elevantur per totalem terrae elevationem; et ita possunt fieri montes altissimi. Et si nulli essent modo montes, adhuc per istum modum fierent in futuro; nec apparent alii modi per quos possent generari et manere tales montes. Aliqui enim ponunt quod ex motibus terrae, per exhalationes, generantur montes. Sed si hoc esset verum de aliquibus 25 parvis montibus, tamen de altissimis montibus et longissimis non possit hoc esse verum; quia ubi esset tanta exhalatio inclusa, quae tantam terram posset elevare, non apparet bene; et si esset tanta terra elevata, tamen exeunte exhalatione caderet iterum in foveam suam.

Et sic patet quaestio. 30

COLUMBIA UNIVERSITY.

1. eius om. M. ?. altera] alia M. 4. est medium] fit in centro B. 5. supra] extra M. 9. discoopertum] indiscoopertum B. 10. erat] fuit M. 11. erit] manet M. 18. ergo] igitur M. 20. magis] nimis M. 21. et fluere] nec fluere M. 22-23. Et ... montes] Et simili modo essent montes M1. 24. tales] tanti M. Q6. possit. . . esse] esset M. 28. terra om. M. exhalatione] sua add. M. 30. Et ... quaestio om. B.


Article Contentsp. 415p. 416p. 417p. 418p. 419p. 420p. 421p. 422p. 423p. 424p. 425

Issue Table of ContentsSpeculum, Vol. 16, No. 4 (Oct., 1941), pp. 389-512Front MatterBishop Benno II of Osnabrck[pp. 389-403]The Historical Background of the King of Tars [pp. 404-414]John Buridan on the Habitability of the Earth [pp. 415-425]The One Hundred and Three Names of Noah's Wife [pp. 426-452]De Opere Lemoviceno [pp. 453-458]Some Legends Concerning Eleanor of Aquitaine [pp. 459-468]The Tropology of Mediaeval Dedication Rites [pp. 469-479]Passages from the Coutume de Bretagne [pp. 480-484]The Dates of Three Letters of Petrarch [pp. 485-486]The Date of John the Scot's Annotationes in Marcianum [pp. 487-488]A Note on the Vision of a Certain English Prior [pp. 488-489]ReviewsReview: untitled [pp. 490-491]Review: untitled [pp. 491-492]Review: untitled [pp. 492-493]Review: untitled [pp. 494-496]Review: untitled [pp. 496-497]Review: untitled [pp. 497-499]Review: untitled [pp. 499-501]Review: untitled [pp. 501-503]Review: untitled [pp. 504-505]Review: untitled [pp. 505-506]Review: untitled [pp. 506-507]

Bibliography of Periodical Literature [pp. 508-510]Books Received [pp. 510-511]Communication [pp. 511]Announcement [pp. 512]Back Matter

enrnst a. moody-john buridan on the habitability of the earth

Documents

conditionsjohn buridan

tradition of buridan

documentary mention

jstor terms

jstor archive

terms conditions of

distinguished career

nicholas of oresme