Instances of Descartes’s Early Projectionism: the Correspondence with Ferrier

Instances of Descartes’s Early Projectionism: the Correspondence with Ferrier

Invited editor: Ovidiu BABEȘ

Abstract. This paper investigates Descartes‟s description of a lenscutting machine set forth in his early correspondence with the artisan Jean Ferrier. I argue that this episode of Descartes‟s mixed-mathematical practice goes beyond the traditional Aristotelian model of subalternation of sciences in two ways: (i) it conceives optics as not being bound only to the principles of geometry – as it should be the case for Aristotelian mixed-mathematics, and (ii) it allows for conjoining different types of mixed-mathematics in a way in which certainty is preserved. The knowledge of each of them is seen as transferable to the other. In turn, these particularities are better explained if we take Descartes to have a view on mixed-mathematics which is inspired by Proclus‟s Commentary on the First Book of Euclid’s Elements.

Keywords: Descartes, Ferrier, Proclus, division of sciences, mixed-mathematics, dioptrics

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