Common Sense and Skeptical Reflection
IN THE LAST TWO CHAPTERS, I have described Descartes as structuring reasons for suspense of judgment and reasons for doubt in ways that mark significant departures from the ancient skeptics. I want now to consider how Descartes puts philosophical reflection into relation to prephilosophical common sense. I will again argue that he departs in significant ways from the ancient skeptics, but I will also argue that his way of conceiving this relation is equally remote from our own, and that in at least one important respect he is more like the ancients than he is like us.
Recall that there are two rather different dialectical situations in which relations between common sense and skeptical reflection might have emerged in ancient skepticism. One is the Academic skeptics' reactions to the Stoic doctrine of assent to “cognitive impressions.” The Stoics claimed that each of us has many cognitive impressions, typically sense impressions of a particular sort, and that these cognitive impressions are in one way or another the basis for everything that we can know. A cognitive impression is one that “ arises from what is and  is stamped and impressed exactly in accordance with what is,  of such a kind as could not arise from what is not.”1 The Stoics held that the wise person withholds assent unless he is presented with a proposition suitably related to a cognitive impression. So if a Stoic could be persuaded that no impressions meet all three clauses of the definition, then he would hold that the wise person will withhold assent from every proposition. What the Academic skeptics argued was that no putative cognitive impression is “of such a kind as could not arise from what is not.” The Academics had____________________