DESCARTES'S procedure in the Meditations on First Philosophy is extraordinary. In order to discover the fundamental principles of philosophy, he puts forward the dream argument and the deceiving God argument as reasons for doubt, and he vows to suspend judgment about everything to which those radical skeptical considerations apply. It is hard to imagine a present-day investigation of basic philosophical principles beginning in this way—say, Derek Parfit's Reasons and Persons or John Searle's Intentionality. Of course, there are many reasons why this is so. A few present-day philosophers are dissatisfied with all of the available ways of trying to rescue some sort of knowledge from radical skeptical attack. And many philosophers today would not expect that by showing how to answer the skeptic we would uncover fundamental principles of philosophy; they would expect that once the skeptic had been answered, our claims to knowledge would be much as they were before we raised the radical skeptical worries.
Descartes sees the problems and prospects of philosophy very differently from the way we do. In this introduction, I want to sketch a context that will allow us to develop a sympathetic appreciation of Descartes's extraordinary way of proceeding in the Meditations.
As a preliminary, I want to remind readers of a sequence of discoveries that Descartes claims to make in the Meditations. (I will be examining most of these steps in detail in the chapters to follow.) In the First Meditation, Descartes briefly raises ordinary grounds for doubting beliefs, but he gives his attention mainly to radical grounds for doubt. First he offers the dream argument (and a similar “lunacy” argument), which calls into doubt even the most evident of the beliefs we get from our senses—for example, my present belief that my hand is in front of me. Then he gives us the deceiving God argument (and a similar argument designed for atheists), which calls into doubt not just sense-based beliefs but also beliefs about what we grasp “clearly and distinctly,” like the belief that two plus three equals five. Descartes resolves to suspend judgment about all of the beliefs to which these radical arguments apply, and at the beginning