 Certainty is often explicated in terms of indubitability. This has been done in a variety of ways (see, e.g., Goodman 1952; Unger 1978, p. 328). One prominent account of certainty is suggested by Descartes’s presentation of his famous Archimedean point, the cogito (I am thinking, therefore I exist). In the Second Meditation, Descartes reviews the extensive doubts of the First Meditation before saying that even if “there is a deceiver of supreme power and cunning who is deliberately and constantly deceiving me,” still “he will never bring it about that I am nothing so long as I am something” (PW 2, p. 17). Descartes then concludes that the proposition that he himself exists is true whenever he considers it. It is often thought that the cogito has a unique epistemic status in virtue of its ability to resist even the “hyperbolic” doubts raised in the First Meditation (see Markie 1992 and Broughton 2002). However, even if Descartes took this view of the certainty of the cogito, he did not accept the general claim that certainty is grounded in indubitability. In the Third Meditation, Descartes says that he is certain that he is a thinking thing, and he explains the certainty of this “first item of knowledge” (it is unclear whether he regards it as distinct from the cogito) as resulting from the fact that it is a clear and distinct perception (PW 2, p. 24). (Matters are complicated, however, by the fact that Descartes also says in the Third Meditation that certainty depends on knowing that God exists and is not a deceiver.)