chapter five

DESCARTES, BASSO, AND TOLETUS: THREE KINDS OF CORPUSCULARIANS

There is a general consensus that one of the more important changes in seventeenth century philosophy is the movement from what is various- ly called scholasticism, naturalism, or animism (what the Aristotelians hold) to what is variously called the mechanical philosophy, corpuscu- larianism, or atomism (what the moderns hold): “of central importance to the history of the physical sciences in the seventeenth century and beyond was the revival of the ancient atomistic doctrines of Democri- tus, Epicurus, and Lucretius.”1 This revival is understood as the attempt to explain the characteristic behavior of bodies in terms of the size, shape, and motion of the small particles that make them up; it is usually accom- panied with the elimination of sensory qualities such as heat and cold, color, and taste. Given that atomism was rejected by Aristotle, the emer- gence of the mechanical philosophy appears to entail the rejection of scholastic philosophy. Historians and philosophers do seem to agree on these points: Throughout the scientific circles of western Europe during the first half of the seventeenth century we can observe what appears to be a sponta- neous movement toward a mechanical conception of nature in reaction to Renaissance naturalism. Suggested in Galileo and Kepler, it assumed full proportions in the writing of such men as Mersenne, Gassendi, and Hobbes, not to mention less well known philosophers. [One can add Descartes, Boyle and Newton to the list].2 Even the latest history of the “scientific revolution” accepts this phe- nomenon and its accompanying demarcation into two camps, the Aris- totelians and the moderns, in order to argue that

1 Garber , p. . 2 Westfall, , pp. –. Westfall argues (from a Newtonian perspective) that the conjunction of mechanism and corpuscularianism was detrimental to the scientific revolution, which needed to detach corpuscularian matter theory from mechanical or mathematical theory of motion (chap. ).  chapter five

the superior intelligibility, and therefore the explanatory power, of the mechanical philosophy was more limited than its proponents claimed. Adherents’ conviction that mechanical accounts were globally superior to alternatives, and more intelligible, has to be explained in historical rather than abstractly philosophical terms.3 Indeed, it has been argued that the central philosophical and method- ological problems of early modern philosophy were not posed by Gali- leo’s mechanics or Copernican astronomy, but by the so-called corpus- cular or mechanical philosophy: One of the most persistent, and philosophically disturbing, features of most sciences of the th century was the radical observational inacces- sibility of the entities postulated by their theories. As numerous scholars have shown, it was the epistemological features of this type of theory which occasioned much of the philosophizing of the th and th centuries.4 Now, it happens that Descartes would not have fully agreed with these characterizations. In Principles IV, article , “The philosophy of Dem- ocritus differs from my own just as much as it does from the standard view of Aristotle and others,”5 Descartes explains the relations between his philosophy and those of Aristotle and Democritus in a symmetrical fashion. In the preceding article, Descartes had already claimed that there are particles in each body that are so small they cannot be perceived by the senses. That claim is the only point of agreement between his phi- losophy and that of Democritus: “It is true that Democritus also imag- ined certain small bodies having various sizes, shapes and motions, and supposed that all bodies that can be perceived by the senses arose from the conglomeration and mutual interaction of these corpuscles.”Surpris- ingly, Descartes also presents the claim as a point of agreement between his philosophy as that of Aristotle. Descartes first puts aside the possi- ble objection that the rejection of Democritus’ philosophy might have been based on the fact that it “deals with certain particles so minute as to elude the senses, and assigns various sizes, shapes and motions to them.” According to him, “no one can doubt that there are in fact many such

3 Shapin , p. . 4 Laudan , “A Revisionist Note on the Methodological Significance of Galilean Mechanics,” p. . 5 Of course, the Principles has to be put into context as a teaching text, a work which Descartes hopes might be used in the schools; for that reason, Descartes is surely minimizing the differences between himself and Aristotle and maximizing the differences between himself and Democritus in the Principles. See Ariew .