The defense of reason has had a long history. Descartes played a pivotal role in it, if for no other reason than that he sharply focused on the problem (look no further than the start of the Meditations on First Philosophy), firmly etched the separate domains of reason and religion, and believed that his work would quietly, but firmly, restore reason to its rightful place, not at the periphery of human thought but at its very epicenter. This chapter attempts to construct a sequence of arguments that a skeptic might pose against Descartes' defense of reason.

I begin, in section I, with a brief look at another player in this history, not given much attention by philosophers: Michel de Montaigne. Montaigne was Descartes' precursor, with views on reason that have much bearing on the work of his successor in France. In his book Descartes against the Skeptics, Edwin M. Curley argues that the proof of the existence of God is interlocked with the argument of the cogito in this way: “Descartes would hold that even the proposition ‘I exist’ is fully certain only if the rest of the argument of the Meditations goes through. We must buy all or nothing.” (C, 95) Section II is designed to demonstrate that Curley's view would land Descartes in a paradox from which it would be impossible for him to escape, and would thereby wreck his entire system. But arguing against Curley is not the primary purpose of this section.