Descartes: Overcoming Doubt - Philosophy Pages

Finally, then, Descartes raises even more comprehensive doubts by inviting us to consider a radical hypothesis derived from one of our most treasured traditional beliefs. What if (as religion teaches) there is an omnipotent god, but that deity devotes its full attention to deceiving me? (Med. I) The problem here is not merely that I might be forced by god to believe what something which is in fact false. Descartes means to raise the far more devastating possibility that whenever I believe anything, even if it has always been true up until now, a truly omnipotent deceiver could at that very moment choose to change the world so as to render my belief false. On this supposition, it seems possible to doubt the truth of absolutely anything I might come to believe.

Although the hypothesis of a deceiving god best serves the logical structure of the Meditations as a whole, Descartes offered two alternative versions of the hypothetical doubt for the benefit of those who might take offense at even a counter-factual suggestion of impiety. It may seem more palatable to the devout to consider the possibility that I systematically deceive myself or that there is some evil demon who perpetually tortures me with my own error. The point in each case is that it is possible for every belief I entertain to be false.

Remember that the point of the entire exercise is to out-do the skeptics at their own game, to raise the broadest possible grounds for doubt, so that whatever we come to believe in the face of such challenges will indeed be that which cannot be doubted. It is worthwhile to pause here, wallowing in the depths of Cartesian doubt at the end of the First Meditation, the better to appreciate the escape he offers at the outset of Meditation Two.