CHAPTER FOUR THE MECHANICAL ALTERNATIVE: PERCEPTION AND

Ainsi ie croy que nous auons cy-deuant confondu la notion de la force dont Tame agit dans le corps, auec celle dont vn corps agit dans vn autre.

Descartes to Princess Elisabeth 21 May 1643

Descartes' philosophy is best typified as a "mechanical", or "mechanistic" philosophy. I shall use both of these terms interchangeably. "", "mechanist philosophy", "mechanicism" and the like may however stand for a much broader type of philosophic or scientific reasoning.2 It will have to wait to the next chapter to define the Cartesian type of more precisely. For the time being I shall start with that part of the subject- of philosophy through which the mechanical way of thinking is most easily exemplified: perception theory.

1 Descartes, AT ΙΠ, p. 667. 2 E. J. Dijksterhuis' classic Mechanisation of the World-Picture, opens with a note in which the author explains his terminological preferences: "Het is moeilijk, een geheel bevredigende terminologie vast te stellen. Mechanisch doet te veel aan werktuigelijk in den zin van gedachteloos denken. Mechanistisch ontmoet als zodanig geen bezwaar maar vereist als correspoderend substantief mechanisme, [welk] woord echter ook voor de inwendige samenstelling van een werktuig (mechaniek) in gebruik is. Wij geven daarom de voorkeur aan het substantief mechamcisme ter aanduiding van de denkrichting en begaan dan de inconsequentie, daarnaast het adjectief mechanistisch te gebruiken en van mechanisering van het wereldbeeld te spreken." E. J. Dijksterhuis, De Mechanisering van het wereldbeeld; De Geschiedenis van het natuurwetenschappelijk denken, Amsterdam (Meulenhoff) 19896, p. 1. For Dijksterhuis however, the term mechanisation covers much more than Cartesianism or other seventeenth-century corpuscular philosophies alone. As far as our subject is concerned, the association of "mechanism" with the internal structure of artificial instruments is actually an advantage. The danger moreover that "mechanical" is too easily associated with "thoughtless", is perhaps even greater in Dutch than it is in English. 108 CHAPTER FOUR 4.1 The example of Les Météores Descartes' Météores—the second, that is, of the essays which, in 1637, were published along with the Discours de la Méthode—deals with a large number of subjects, reaching from the corporeal structure of salt to the meteorological phenomena of storms, thunder and rainbows. Besides an interesting variety of topics, however, it also presents a sharp image of Descartes' use of "mechanistic" argumentation.

4.1.1 Suppositions and mechanistic explanations An important point to notice first, is that Descartes' terminology, his sequence of topics and much of his argumentation is wholly Scholastic. As has been pointed out by Etienne Gilson, Descartes' text closely follows that of the Conimbricenses' commentary on Aristotle's Meteorology.3 In fact, resemblances between Descartes and Aristotle are often so great, that they must have been obvious to any contemporary who had studied Aristotle's views or those of his commentators.4 It is therefore all the more interesting that Descartes presents his meteorological essay as a sample of the new method which he had claimed to have developed in the preceding Discours de la Méthode. Descartes does not seek complete originality as regards his ideas on meteorological phenomena. What he does claim, is to have found "general principles of Nature" on which a correct understanding of these phenomena is supposed to depend. As it is said in the discours premier of the Météores: It is true that since the knowledge of these depends on the general principles of Nature, which, as far as I know, have not yet been well explained, I must, at the start, make use of some suppositions, just as I have done in the Dioptrics; but I shall aim to

3 Etienne Gilson, "Météores Cartésiens et Météores Scolastiques", in Etienne Gilson, Études sur le rôle de la pensée médiévale dans la formation du système cartésien, Paris (Librairie philosophique J. Vrin) 19845, pp. 102-137. 4 See e.g. the passages from Les Météores, AT VI, pp. 231 and 232 in Gilson, Index, pp. 180-181. These and other passages are also referred to in Ferdinand Alquié's edition of excerpts from the Météores, in René Descartes, Œuvres philosophiques, Textes établis, pésentés et annotés par Ferdinand Alquié, Paris (Gamier) 1963, Tome I, pp. 719-761.