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cientific and cultural center in Prague after 1620. ThePrague edition of the tables remained almost un-noticed, and only a few copies were saved ; probablythe only complete copy is kept, together with thehandwritten "instruction," in the library at Danzig .Thus, Burgi's greatest discovery had no apparentinfluence on the development of science .

BIBLIOGRAPH Y

Burgi's only published work is Arithmetische and geo-metrische Progress -Tabu len, sambt griindlichem Unterricht,wie solche niltzlich in allerley Rechnungen zu gebrauchen,and verstanden werden sol (Prague, 1620),repr . in H. R.Gieswald, Justus Byrg als Mathematiker and dessen Ein-leitung zu seinen Logarithmen (Danzig, 1856).

There is neither a detailed biography nor an analysis ofBurgi's scientific work . Basic bibliographic data in thefollowing works can be of use : G . Vetter, "Dejiny mate-matickych ved v ceskych zemich od zalo2eni universityv r.1348a2 do r.1620"("History of Mathematics in theBohemian Lands From the Foundation of the Universityin 1348until 1620"),in Sbornik pro dejiny pIirodnich veda techniky (Prague), 4 (1958), 87-88; and "Kratkii obzorrazvitija matematiki v cheshtskikh zemliakh do Belo-gorskoi bitvy," in Istoriko-matematicheskie issledova-niya,11(Moscow, 1958), 49, 512; E. Voellmy, "Jost Burgiand die Logarithmen," in Beihefte zur Zeitschrifi fur Ele-mente der Matheniatik, no. 5 (1948); and E. Zinner,Deutsche and niederldndische astronomische Instrumente des11.-18. Jahrhunderts(Munich, 1956), pp. 268-276.

Luso~ Nov'l

BURIDAN, JEAN (b.Bethune, France, ca.1295; d.Paris, France, ca.1358),philosophy, logic, physics.

Although Jean Buridan was the most distinguishedand influential teacher of natural philosophy at theUniversity of Paris in the fourteenth century, littleis known of his personal life . He was born in thediocese of Arras, and went as a young cleric to studyat the University of Paris, where he was first enrolledas a student in the College of Cardinal Lemoine andlater became a member of the College of Navarre .It is probable that he obtained his master of artsdegree soon after 1320, since a document dated 2February 1328 mentions him as rector of the univer-sity in that year . Other documents, relating to bene-fices whose revenues provided his financial supportand bearing the dates 1329, 1330, 1342, and 1348,describe him as a "very distinguished man," as a"celebrated philosopher," and as "lecturing at Parison the books of natural, metaphysical, and moralphilosophy." Two passages in his own writings indicatethat at some date prior to 1334 he made a visit to

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the papal court at Avignon and, on the way, climbedMt. Ventoux in order to make some meteorologicalobservations.

In 1340 Buridan was rector of the university fora second time, and in that year he signed a statuteof the faculty of arts which censured certain mastersfor the practice of construing texts in a literal senserather than in accordance with the intentions of theauthors, warning that this practice gave rise to "intol-erable errors not only in philosophy but with respectto Sacred Scripture ." One of the articles of censurebears on a statement known to have been made byNicolaus -of Autrecourt, whose skeptical views oncausal inferences were attacked by Buridan in his ownwritings . The last documentary mention of Buridanoccurs in a statute dated 12 July 1358, where his nameappears as witness to an agreement between the Picardand English nations of the university . It is not unlikelythat he fell victim to the Black Plague, which in 1358took the lives of many of those who had managedto survive its first outbreak in 1349.

Buridan was a secular cleric rather than a memberof a religious order, and he remained on the facultyof arts to the end of his life without, apparently,seeking to obtain a degree in theology. In his lifetimehe was held in high esteem by his colleagues, students,and ecclesiastical superiors; and for nearly two cen-turies after his death his teachings in natural philoso-phy and logic were of paramount influence in theuniversities of northern and eastern Europe. A docu-ment in the archives of the University of Cologne,dated 24 December 1425, speaks of the precedingcentury as "the age of Buridan," and when GeorgeLockert, in 1516, edited one of Buridan's works, hestated that Buridan still ruled the study of physicsat Paris . In later centuries, the story of the ass whostarved to death because he could not choose betweentwo equally desirable bundles of hay was attributedto Buridan, and another story, presumably legendarybut perpetuated by the poet Francois Villon, relatedthat Buridan had been involved in scandalous rela-tions with the wife of Philip V of France and had,by the king's order, been tied in a sack and throwninto the Seine.

The extant writings of Buridan consist of the lec-tures he gave on subjects in the curriculum of thefaculty of arts at Paris . In the fourteenth century thiscurriculum was based largely on study of the treatisesof Aristotle, along with the Summulae logicales ofPeter of Spain and other medieval textbooks ofgrammar, mathematics, and astronomy. Buridancomposed his own textbook of logic, Summula dedialectica, as a "modern" revision and amplificationof the text of Peter of Spain ; he also wrote two

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treatises on advanced topics of logic, entitled Con-sequentiae and Sophismata, which are among themost interesting contributions to late medieval logic .All of his other works are in the form of commentariesand of critical books of Questions on the principaltreatises of the Aristotelian corpus . The literal com-mentaries are extant only in the unpublished manu-script versions, but the books of Questions on Aris-totle's Physics, Metaphysics, Deanima, Parvananuralia,Nicomachean ethics, and Politics were published,along with Buridan's writings in logic, after the in-vention of the printing press .

The only modern edition of a work by Buridan isthat of his Questions on Aristotle's De caelo et mundo,previously unedited, which appeared in 1942. Mostof the printed editions represent the lectures Buridangave during the last part of his teaching career,although earlier versions are to be found among theunpublished manuscript materials . Until a criticalstudy of the manuscripts is made, however, there isno sure way of determining any order of compositionfor Buridan's works, nor of tracing the developmentof his thought over the thirty-odd years of his aca-demic career.

Buridan made significant and original contributionsto logic and physics, but as a philosopher of sciencehe was historically important in two respects . First,he vindicated natural philosophy as a respectablestudy in its own right . Second, he defined the objec-tives and methodology of scientific enterprise in amanner that warranted its autonomy with respect todogmatic theology and metaphysics ; this achievementwas intimately connected with the fourteenth-centurymovement known as nominalism and with the con-troversies precipitated at the universities of Oxfordand Paris by the doctrines associated with Williamof Ockham . Buridan's own philosophical position wasthoroughly nominalistic, and indeed very similar tothat of Jean de Mirecourt, a theologian of Paris whoseteachings were condemned in 1347 by the chancellorof the university and the faculty of theology . Buridanhimself was able to escape the charges of theologicalskepticism that were directed against his fellow nomi-nalists of the theological faculty . He owed his goodfortune in part, no doubt, to his prudence and diplo-macy. Primarily, however, he could ward off criticismfor the fundamental reason that he employed thelogical and epistemological doctrines of nominalismin a methodological, rather than a metaphysical, wayin formulating the character and the evidential foun-dations of natural philosophy .

The formal logic presented in Buridan's Sunimulade dialectica is closely related, in topical structure andterminology, to the so-called terminist logic of thethirteenth century, represented by the textbooks of

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William of Sherwood and Peter of Spain . Althoughit presupposes the nominalist thesis that general termsare signs of individuals, and not of common naturesexisting in individuals, it does not exhibit any strongevidence of direct influence by the logical writingsof Ockham ; it may well have been developed inde-pendently of such influence on the basis of the modernlogic (logica moderna) already well established in thearts faculties of Oxford and Paris. The doctrine ofthe supposition of terms, basic to this logic, is usedin defining the functions of logical operators or syn-categorematic signs in determining the truth condi-tions of categorical propositions of various forms andin formulating the laws of syllogistic inference, bothassertoric and modal . Treatises on topical arguments,fallacies, and the demonstrative syllogism concludethe work.

Buridan's Sophismata, designed to constitute a ninthpart of the Summula, apparently was written muchlater in his life, for it contains criticisms of the theoryof propositional meanings, or complexe signift'cabilia,which Gregory of Rimini introduced in 1344. Thiswork presents a fully developed analysis of meaningand truth which corresponds closely to that ofOckham's Summa logicae. It goes beyond the workof Ockham, however, in presenting original and highlyadvanced treatments of the problem of the nonsub-stitutivity of terms occurring in intensional contextsand the problem of self-referential propositions rep-resented by the Liar paradox . Buridan's treatment ofthese problems exhibits a level of logical insight andskill not equaled until very recent times . His treatiseConsequentiae, which develops the whole theory ofinference on the basis of propositional logic, marksanother high point of medieval logic, the significanceof which has been appreciated only in the twentiethcentury.

Buridan's philosophy of science is formulated inhis Questions on the Metaphysics, and is applied tothe concepts and problems of natural science in hisQuestions on the Physics.The Aristotelian definitionof science as knowledge of universal and necessaryconclusions by demonstration from necessary, evident,indemonstrable premises is accepted. A sharp dis-tinction is made, however, between premises in whichthe necessity is determined by logical criteria or bystipulated meaning of the terms, and those in whichevidence rests on empirical confirmation and whichare called necessary in a conditional sense, or "onthe supposition of the common course of nature ."Only in the latter sense do the principles of the naturalsciences have evidence and necessity.

These principles are not immediately evident ; indeedwe may be in doubt concerning them for a long time .

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But they are called principles because they are inde-monstrable, and cannot be deduced from other premisesnor be proved by any formal procedure ; but they areaccepted because they have been observed to be truein many instances and to he false in none .'

The significance of this theory of scientific evidencelies in its rejection of the thesis, held by most of thescholastic commentators on Aristotle, that the princi-ples of physics are established by metaphysics andthat they are necessary in the sense that their con-tradictories are logically or metaphysically impossible .This metaphysical interpretation of Aristotelianphysics led Bishop Etienne Tempier and the facultyof theology at Paris to condemn, in 1277, doctrinestaught by members of the arts faculty as truths neces-sary to philosophy, although contradictory to dogmasof the Christian faith . By construing the principlesof the sciences of nature as inductive generalizationswhose evidence is conditional on the hypothesis ofthe common course of nature, Buridan was able toconcede the absolute possibility of supernatural in-terference with the natural causal order, and yet toexclude such supernatural cases as irrelevant to thepurposes and methodological procedures of thescientific enterprise . Nicolaus of Autrecourt, de-manding that scientific principles have absolute neces-sity and certainty, had argued that a science of naturebased on causal laws established by inductive gen-eralization had no evidence whatsoever, since it couldnot be known in any given instance whether or notGod was producing an effect without a natural cause .Buridan refers to Nicolaus' position in these words :

It has hereby been shown that very evil things are beingsaid by certain ones who seek to undermine the naturaland moral sciences because absolute evidence is notpossessed by most of their principles and conclusions,it being supernaturally possible for them to he renderedfalse . For in these sciences absolutely unconditionalevidence is not required, and it is enough if we haveconditional or hypothetical evidence of the kind de-scribed above.'

The conception of scientific enterprise formulatedby Buridan as a means of justifying its pursuit withinthe framework of the Christian doctrine of divineomnipotence is the conception within which sciencehas operated since the late seventeenth century. Tomake science compatible with Christian dogma,Buridan had to break its traditional ties with meta-physics and define its principles methodologically, interms of their value in "saving the phenomena ." Hestill encountered some theological difficulties in ap-plying this method within the domain of physics, asdid Galileo three centuries later ; but after the timeof Buridan, natural philosophy had its own legitimacy

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and ceased to be either only a handmaiden of theologyor a mere exposition of the doctrines of Aristotle .The Questions composed by Buridan on problems

raised in Aristotle's Physics and De caelo et mundoexhibit his application of these criteria of scientificmethod and evidence to the critical evaluation ofAristotle's theories and arguments and to the diverseinterpretations of them offered by Greek, Moslem,and Christian scholastic commentators . The generalscheme and conceptual framework of analysis, withinwhich Aristotle's physics and cosmology are formu-lated, is accepted by Buridan as the working hypothe-sis, so to speak, of natural philosophy. But the schemeis not sacrosanct, and Buridan not infrequently enter-tains alternative assumptions as being not only logi-cally possible but also possibly preferable in account-ing for the observed phenomena. While the authorityof Aristotle had often been challenged on the groundthat his positions contradicted Christian doctrine, ithad come, in Buridan's time, to be challenged ongrounds of inadequacy as a scientific account ofobserved facts . Buridan's major significance in thehistorical development of physics arises from just sucha challenge with respect to Aristotle's dynamic theoryof local motion and from his proposal of an alternativedynamics which came to be known as the impetustheory.

An obvious weakness of Aristotle's dynamics is itsinability to account for projectile motions, such as theupward motion of a stone thrown into the air afterit has left the hand of the thrower . According to theassumptions of Aristotelian physics, such a motion,being violent and contrary to the natural movementof the stone toward the earth, required an externalmoving cause continuously in contact with it . Sincethe only body in contact with it is the air, Aristotlesupposed that in some way the air pushes or pullssuch a body upward. This feeble explanation drewcriticism in antiquity and from medieval Moslemcommentators and gave rise to a theory that theviolent action of the thrower impresses on the stonea temporary disposition, of a qualitative sort, whichcauses it to move for a short time in the directioncontrary to its nature . This disposition was called animpressed virtue (virtus impressa), and it was held tobe self-expending and quickly used up because of itsseparation from its source . Franciscus de Marchia, aFranciscan theologian who taught at Paris around1322, gave a full presentation of this theory, and itis likely that Buridan was influenced by it .

In treating of the problem of projectile motion inhis Questions on Aristotle's Physics (VIII, question12), Buridan expounded Aristotle's theory of propul-sion by the air and rejected it with arguments similarto those that Marchia had used . His own solution was

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in some respects like that of Marchia, but in onecrucial point it was strikingly different . The tendencyof the projectile to continue moving in the directionin which it is propelled, which Buridan calls impetusrather than virtus impressa, is described as a perma-nent power of motion, which would continue un-changed if it were not opposed by the gravity of theprojectile and the resistance of the air . "This impetus,"he says in another discussion given in his Questionson the Metaphysics, "would endure forever [ad in-finitum] if it were not diminished and corrupted byan opposed resistance or by something tending to anopposed motion."3

The suggestion given here of the inertial principlefundamental to modern mechanics is striking, as aresome further uses that Buridan makes of the impetusconcept in explaining the accelerated velocity of freefall, the vibration of plucked strings, the bouncingof balls, and the everlasting rotational movementsascribed to the celestial spheres by Greek astronomy .Buridan defines impetus in a quantitative manner,as a function of the "quantity of matter" of the bodyand of the velocity of its motion ; thus, he seems toconceive of impetus as equivalent to what in classicalmechanics is called momentum, defined as the productof mass and velocity . In treating the action of gravityin the case of freely falling bodies, Buridan construesthis action as one imparting successive increments ofimpetus to the body during its fall .

It must be imagined that a heavy body acquires fromits primary mover, namely from its gravity, not merelymotion, but also, with that motion, a certain impetussuch as is able to move that body along with the naturalconstant gravity . And because the impetus is acquiredcommensurately with motion, it follows that the fasterthe motion, the greater and stronger is the impetus . Thusthe heavy body is moved initially only by its naturalgravity, and hence slowly ; but it is then moved by thatsame gravity as well as by the impetus already acquired,and thus it is ...continuously accelerated to the end .'

The effect of a force, such as gravity, is thus con-ceived of as a production of successive increments ofimpetus, or of velocity in the mass acted upon,throughout the fall.It is a short step from this to themodern definition of force as that which changes thevelocity of the body acted upon, implying the cor-relative principle that a body in uniform motion isunder the action of no force. Buridan does not quitetake this step, since he retains the Aristotelian assump-tion that a constant cause must produce a constanteffect, and ascribes the increase in velocity to theaddition of impetus as an added cause acting alongwith the gravity .

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Yet his theory obviously requires a distinctionbetween impetus as a "conserving cause" of motionand gravity as a "producing cause" of the motionconserved by the impetus ; his failure to draw theconsequence of this distinction was perhaps becausehe did not attempt a mathematical analysis involvingthe concept of instantaneous velocities added con-tinuously with time . Whether Buridan construed theacceleration as uniform with respect to time elapsed,or with respect to distance traversed, is not clear . Heprobably regarded the two functions as equivalent,a view that, however impossible from a mathematicalpoint of view, was retained into the seventeenthcentury, when Descartes and Galileo (in his letter toSarpi of 1604) sought to prove that velocity increasesin proportion to time elapsed from the premise thatvelocity increases in direct proportion to distance offall.

Buridan's concept of impetus is further distin-guished from the modern inertial concept by the factthat he construes rotational motion at uniform angularvelocity as due to a rotational impetus analogous tothe rectilinear impetus involved in projectile motion .Galileo did likewise, and was in this respect nearerto Buridan than to Newton . But Buridan makes astriking use of his impetus concept, in its rotationalsense, by arguing that since the celestial spheresposited by the astronomers encounter no externalresistance to the rotational movements and have nointernal tendency toward a place of rest (such as heavyand light bodies have), their uniform rotationalmotions are purely inertial and require no causesacting on them to maintain their motions . There is,therefore, no need to posit immaterial intelligencesas unmoved movers of the heavenly spheres, in themanner that Aristotle and his commentators supposed ."For it could be said that God, in creating the world,set each celestial orb in motion ...and, in settingthem in motion, he gave them an impetus capableof keeping them in motion without there being anyneed of his moving them any more. It was in thisway, Buridan adds, that God rested on the seventhday and committed the motions of the bodies he hadcreated to those bodies themselves.

It is clear that Buridan's impetus theory markeda significant step toward the dynamics of Galileo andNewton, and an important stage in the gradual disso-lution of Aristotelian physics and cosmology . Buridandid not, however, exploit the potentially revolutionaryimplications of his analysis of projectile motion andgravitational acceleration, or generalize his impetustheory into a theory of universal inertial mechanics .Thus, in discussing the argument of Aristotle againstthe possibility of motion in a void, Buridan accepted

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the principle that the velocity of a natural motionin a corporeal medium is determined by the ratio ofthe motive force to the resisting force of the medium,so that if there were no resisting medium, the motionwould be instantaneous . This is scarcely consistentwith the analysis of gravitational acceleration as finiteincrements of impetus given to the falling body byits gravity, and Buridan made no effort to harmonizethese two different approaches within a commontheory.

In a question bearing on the De caelo et mundo,Buridan asks whether it can be proved that the earthis at rest, with the celestial spheres rotating aroundit, as Aristotle supposed . He states that many peopleof his time held it to be probable that the earth rotateson its own axis once a day and that the stellar sphereis at rest. And he adds that it is "indisputably truethat if the facts were as this theory supposes, every-thing in the heavens would appear to us just as itnow appears.116In support of the hypothesis, heinvokes the principle that it is better to account forthe observed phenomena by fewer assumptions or bythe simplest theory, and argues that since the earthis a small body and the outer sphere is a very largeone, it is more reasonable to attribute the rotationto the earth than to suppose the enormously fasterrotation of the much larger sphere . After giving thisand other arguments in favor of the theory of diurnalrotation of the earth, Buridan makes it quite clearthat they cannot be refuted by any of the traditionalarguments purporting to prove that the earth is atrest. He says that for his part he chooses to hold thatthe earth is at rest and the heavens in motion ; andhe offers, as a "persuasion" for this view, the argumentthat a projectile thrown straight upward from theearth's surface will fall back to the same spot fromwhich it was thrown.

This argument does not seem consistent withBuridan's own impetus theory, unless he had in minda point made later by his pupil Albert of Saxony,who held that the lateral impetus shared by theprojectile with that of the surface of the rotating earthwould be insufficient to carry it over the greater arcwhich it would have to traverse, when projectedoutward from the earth's surface, in order to fall backat the same spot . Not only Albert of Saxony, but alsoanother pupil of Buridan's, Nicole Oresme, took overthis discussion of the earth's rotation ; Oresme con-cluded that it is impossible to prove either side ofthe question, since the motion is purely relative .Oresme said that he accepted the view that the earthis at rest, but only because this seemed to be assumedby the Bible . It is of interest to note that when Coper-nicus was a student at Cracow, Buridan's works in

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physics were required reading in the curriculum of thatuniversity.

While rejecting the theory of the diurnal rotationof the earth, Buridan says that the earth is not immo-bile at the center of the world, and proves it as follows :Because the dry land protruding from the ocean ismostly on one side of the earth, the center of volumeof the earth does not coincide with its center of gravity .The earth, however, is the center of the world in thesense that its center of gravity is equidistant from theinner surface of the celestial spheres . But this centerof gravity is continuously altered by the erosion ofthe dry land, which slowly gets washed into the sea ;and consequently the whole mass of the earth slowlyshifts from the wet side to the dry side in order tokeep its center of gravity at the cera,er of the universe .

Buridan's significance in the history of science liesmore in the questions he raised than in the answershe gave to them, although in some cases his answersopened up new theoretical possibilities that wereundoubtedly influential in the rise of modern me-chanics in the seventeenth century . The impetustheory was taken over by Buridan's pupils and wasmade known throughout central Europe, although ina degenerate form that fused it with the older theoryof a self-expending virtus impressa and introduced anumber of confusions and errors that Buridan himselfhad avoided . It was in this degenerate form that itwas conveyed to Galileo by his teacher Buonamici,so that Galileo had to take the step that Buridan hadtaken three centuries earlier when he discardedMarchia's theory of the self-expending impressed forcein favor of impetus as an enduring condition onlychanged or diminished by opposed forces . Buridan'sapplication of the impetus concept to the analysis offree fall, although retained and made known by Albertof Saxony, was forgotten by most of the later teachersof physics, even when they retained the concept indealing with projectile motion.

Even when Buridan's specific contributions tophysical problems were forgotten, however, the in-fluence of his conception of scientific evidence andmethod remained operative ; and it may be said thatthe idea of mechanics, in the modern sense, becameestablished in early modern times through the workof Buridan and of his contemporaries . In particular,Buridan may be credited with eliminating explana-tions in terms of final causes from the domain ofphysics, which he does very explicitly in his Questionson the Physics (II, questions 7 and 13) and in hisQuestions on the De caelo et mundo (II, question 8).The mechanistic conception of nature, construed asa methodological assumption more than as a meta-physical thesis, emerged in the fourteenth century as

BIBLIOGRAPH )'

I. ORIGINAL WORKS. Early editions of Buridan's worksinclude Quaestiones super decent libros Ethicorum Arisvotelisad Niconnacheunt (Paris, 1489, 1513, 1518; Oxford, 1637):Sophismata Buridani (Paris, 1489, 1491, 1493: best ed ., byAntonius Denidel and Nicolaus de Barra, Paris, ca. 1495),trans. by Theodore K . Scott asJohn Buridan: Sophismson Meaning and Truth (New York, 1966): Summula dedialectica, with commentary by John Dorp of Leiden(Lyons, 1490, 1493. 1495, 1510: as Perotile compendiumtotius logicaeJoannis Buridani, Venice, 1499: there are manylater editions) : Consequentiae Buridani (Paris, 1493. 1495.1499); Quaestiones super octo phvsicorurn libros Aristotelis,ed . Johannes Dullaert Gandavensis (Paris. 1509, 1516);Quaestiones et decisiones physicales insigoiunt virortan ...ed . Georgius Lockert (Paris, 1516), which containsQuaestiones in libros De anima, De sensu et sensato, Demennoria et rentiniscentia, De sornno et vigilia, De longltudineet brevitate vitae, and De iuventate et seneciute : In Meta-ph )-siren Aristotelis quaestiones argutissimae magislri Joann i .sBuridani (Paris. 1518): and Quaestiones in octo librosPoliticoruni (Paris, 1530: Oxford, 1640).

More recent editions are Quaestiones super libros quattuorDe caelo et mundo, ed . E. A. Moody (Cambridge. Mass.,1942); and "Giovanni Buridano, Tractatus de supposi-tionibus," ed . Maria Eleina Reina, inRivista critica di storiadella filosofia, 12(1957), 175-208, 323-352.

A list of manuscripts of Buridan's works, both publishedand unpublished, can be found in Edmond Faral, "JeanBuridan, Notes sur les manuscrits, les editions et Ie contenude ses oeuvres," in Archives d'histoire doctrinale et littdrairedu moven-age, 15(1946), 1-53.11. SECONDARY LITERATURE. Works on Buridan include

J . Bulliot, "Jean Buridan et le mouvement de la terre,"in Revue de philosophic.25(1914), 5-24: Marshall Clagett,The Science of Mechanics in the Middle Ages ( Madison,Wis., 1959), 505-599; E . J. Dijksterhuis,De Mechaniseringvan het Werelbild (Amsterdam, 1915): Pierre Duhem, Etudessur Leonard tie Vinci, II (Paris, 1909), 379-384, 420-423,431-438, and III (Paris. 1913), 1-259, 279-286, 350-360:

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a natural development from Buridan's philosophy ofscience . He was not an experimental scientist or amathematical physicist ; but as a philosopher of sciencehe did much to clear the way for, and to point theway to, the development of modern science in thesedirections .

NOTES

1.Qu. in Meniph.11.Qu. 2(1518). fol. 9r.

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Pierre Duhem, Lest •stdme du monde, Vols. VI-VII (Paris,1954-1958); and Edmond Faral, "Jean Buridan, maitre-es-arts de I'Universite de Paris," in Histoire littdraire dela France, 38 (1949), 462-605.The following works of Anneliese Maier should be

consulted : Die Vorlau fer Galileis im 14. Jahrhundert(Rome.1949); Zwei Grundprobleme der scholastischen Naturphilo-sophie, 2nd ed. (Rome, 1951), 201-235; MetaphisischeHintergrunde der spaischolastischen Natu philosophie(Rome, 1955), 300-335, 348 f., 384fl'.; "Die naturphiloso-phische Bedeutung der scholastischen Impetustheorie," inScholastik, 30(1955), 321-343; and Zwischen Philosophicand Mechanik (Rome, 1958), 332-339.

Also of value are works by E . A. Moody: "John Buridanon the Habitability of the Earth," in Speculun :, 16(1941),415-425; "Ockham, Buridan, and Nicholas of Autrecourt ."in Franciscan Studies, 7 (June, 1947), 113-146; "Galileoand Avempace : The Dynamics of the Leaning TowerExperiment," in Journal of the History of Idea .',12( 1951),163-193,375-422: Truth and Consequence in Medieval Logic(Amsterdam, 1953); and "Buridan and a Dilemma ofNominalism," in Harry Ausn_yn Wolfson Jubilee Volume(Jerusalem, 1965), 577-596.

Additional works concerning Buridan are Karl Prantl,Geschichte der Logik inn Abendlande, IV (Leipzig, 1870),14-38; A. N. Prior, "Some Problems of Self-reference inJohn Buridan," in Proceedings of the British Academy, 48(1962),281-296; Maria Eleina Reina, "Note sulla psicologiadi Buridano," in Arti grafiche grisetti (Milan, 1959), p. 9f'.: Maria Eleina Reina, "Il problema del linguaggio inBuridano," in Rivista critica di storia della jilosofia, 15(1959), 367-417, and15(1960), 141-165,238-264; TheodoreK. Scott, "John Buridan on the Objects of DemonstrativeScience," in Speculum, 40(1965), 654-673; (i . FedericiVescovini, "La concezione della natura di GiovanniBuridano," in La filosofia della natura nel nicdievo : Attidel III Congresso Internazionale di Filosofia Medievale(Milan, 1964): G . Federici Vescovini,Siudi sulla prospettivamedievale (Turin, 1965), 137-163: James J . Walsh, "Buridanand Seneca ." inJournal of tine History of Ideas . 27(1966),23-40: and James J . Walsh, "Nominalism and the Ethics:Some Remarks About Buridan's Commentary," in Journalof the History of Philosophy, 4 (1966), 1-13.

ERNEST A. MOODY

BURLEY, WALTER (b. England, ca. 1275; d. ca.1345?),logic, natural philosophy.

A colophon to the final version of Burley's com-mentary on the Logica vetus that is dated 1337 stipu-lates that the work was composed in its author'ssixty-second year, a factor which places Burley's birthabout 1275, possibly in one of the two towns namedBurley in Yorkshire . Although almost nothing isknown of his youth, it seems most reasonable topresume that Burley began his studies at Oxfordsometime during the last decade of the thirteenthcentury, for two works dated 1301 and 1302 already

2. Ibid., Qu. 1 (1518), fol. 9r .3 . Ibid. (1518). fol.73r.4.Qu. De caelo et nuuulo (1942),180.5. Qu.in Pln •s.V111.Qu. 12. fol. 121r.6.Qu. De caelo ei msntdo 11, Qu. 22 (1942),227.