Aristotelian Commentaries and Scientific Change: The Parisian Nominalists on the Cause of the Natural Motion of Inanimate Bodies

EDITH DUDLEY SYLLA

Following the lead of Pierre Duhem, historians of medieval science have long studied the work of medieval natural philosophers with an eye to seeing how it led or did not lead to the emergence of modern science in the seventeenth century. If one accepts the view of Duhem and others that quite a lot of good natural philosophy was done by fourteenth-century scholastic Aristotelians such as John Buridan, Nicole Oresme, and Albert of Saxony at Paris, and Thomas Bradwar- dine, William Heytesbury, and Richard Swineshead at Oxford, then the question may arise why it took so long for modern science to break away from scholastic Aristotelianism to produce the new physics of the likes of Galileo, Descartes, and Newton. Edward Grant has proposed that it was, in part, the commentary form that brought it about that scholastic Aristotelians absorbed a multitude of small variations on Aristotle without overturning the whole system to replace it with 2 something new and better.2 My project in this paper is to study scholastic Aristotelian commen- taries on the Physics to see the impact of their form, and of the social and institutional context in which they were written, on their content, and on how they worked as a form of scientific practice. There are obviously too many commentaries of too great a length over far too

I See John Murdoch, Pierre Duhemand the History of Late MedievalScience and Philosophy in the MedievalWest, in: Gli studi di filosofiamedievale fiaotto et novecento,eds. R. Imbach and A. Maieru, Rome 1991, 253-302. 2 Edward Grant, Aristotelianismand the Longevityof the Medieval World Viewin: History of Science, 16 (1978), 98. Grant suggests that the Aristotelian commentary form helped to cause the stagnation of science by atomizing it: burying new ideas in isolated contexts, never requiring a commentator to ask himself whether the answer he gave to one question was consistent with the moves he made in response to other questions. This paper began as a talk delivered at the History of Science annual meeting in Madison, Wisconsin, in November 1991 in a session honoring Edward Grant on the occasion of his sixty-fifth birthday. Part of my methodology was to examine this "Grant thesis." I want to thank Professor Grant for his commentary on this earlier occasion.

37 long a period to make a global study of what was going on. The Jesuits writing commentaries at the Collegio Romano, whose works, as William Wallace has shown, influenced the young Galileo, may have had different methods and have worked in a somewhat different institutional and social context than, say, Buridan and Oresme at Paris more than two centuries earlier.3 Here I can only do a case study, to be joined at a later date by further studies of different ques- tions and contexts. I chose to begin with a study of the related commentaries of John Buridan, Nicole Oresme, Albert of Saxony, and Marsilius of Inghen, often classed together as the Parisian nominalists, because they are often considered to be among the most outstanding fourteenth-century scientific thinkers and we have commentaries on the Physics by each of them. I could not, however, do a comprehensive study of all of their Physics commentaries, so, wanting to consider a topic that the authors themselves would have considered central, I chose a question that Nicoletto Vernia in his Tractatus de gravibus et levibus of ca. 1475 called the questio physica graaissima, namely the question of why heavy bodies naturally move down and light bodies up, a question which is typically 4 raised in connection with Chapter 4 of Book 8 of Aristotle's Physics.4

3 See William A. Wallace, ReinterpretingGalileo on theBasis of His Latin Manuscripts,in: ReinterpretingGalileo, ed. William A. Wallace, Washington, D.C. 1986, 3-28 (Studies in Philosophy and the History of Philosophy, vol. 15). 4 Anneliese Maier, An der Grenzevon Scholastikund Naturwissenschaft,2nd. ed., Rome 1952, 144, quoting Nicoletto Vernia, Tractatus de graUibuset leaibus, Venice 1504: "Haec questio inter omnes physicas quaestiones gravissima est." In this paper I go over ground already ably covered by Anneliese Maier in the above work, but in addi- tion to looking at opinions on the cause of elemental natural motion, I try to under- stand the scholastic Aristotelian commentary tradition as a way of doing science with certain characteristic properties. For the theoretical context within which the authors I discuss were working, Anneliese Maier provides an excellent and thorough survey, which I will not repeat here. Maier covers, for instance, 146, the distinction between motusper se and motusper accidens;between per se and ab alio; 147-48, between potentia essentialisand potentialaccidentalis; and, 149, between actus Primus and actus secundus. Edward Mahoney has recently made a preliminary study of Vernia's Tractatus de gravibuset leaibus,of which he has found an edition of 1474 or 1476, making it Vernia'ss earliest published work. See Edward Mahoney, Philosophyand ,Sciencein NicolettoVernia, and Agostino Nfo, in: Scienza e filosofia all'Università di Padova nel Quattrocento,ed. Antonino Poppi, Padua 1983, 137-42. The work appears together with Gaetano of Thiene, De Coeloet Mundo, Padua 1474?. It was later printed together with Vernia's Contraperversam Averroes opinionem de unitate intellectus,Venice 1505. In Nicolettohernia's s Annotationson John of Jandun's De anima in: Historia PhilosophiaeMedii Aeai, eds. Burkhard Mojsisch and Olaf Pluta, Amsterdam/Philadelphia 1991, 573, Edward Mahoney identifies a copy of John of Jandun's questions on the Physics(Venice 1488) found in the Biblioteca Universitaria at Padua (shelfmark Sec. XV. 665) as originally

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