Abstract

In 1697, the publication of a letter from Leibniz to Bourguet in the Journal des Sçavants prompted a vigorous reply from the Cartesien Pierre-Sylvain Regis, leading to a public exchange between the two philosophers. The controversy ended with a contribution by Regis who seemingly got the final word. The exchange mainly focused on Descartes’s Principles of philosophy, III, art. 47, a text where Descartes held that the world would eventually take all the possible forms it is capable of. While Leibniz maintained that this claim had inescapable Spinozistic consequences, Regis defended Descartes against the accusation. Each position relied on its own distinct conception of the world’s infinity. This chapter follows this controversy step by step. I show in particular that Leibniz, although he did not write it, had a forceful reply to Regis’s final published objections ready at hand, based on his rehabilitation of the notion of actual infinity.