Ports of Call  


The Cogito -- "I am thinking, therefore I exist."

The evil demon hypothesis is an extraordinarily powerful skeptical hypothesis. Arguably, nothing like it can be found in earlier skeptical literature. We have already seen that this hypothesis can call into question everything which could not be doubted on the dream hypothesis. So, is there anything which can withstand the overwhelming power of such an evil demon? As it turns out, remarkably enough there is. Descartes finally considers whether the demon can deceive him into thinking that he exists when in fact he does not exist. Upon considering this, Descartes concludes that he cannot be deceived into thinking that he does not exist when in fact he does, for unless something existed there would be nothing to deceive! So, he has found one truth which he can know with absolute certainty! This represents the end point of what I shall call the first application of the method of doubt and the method of analysis. Note that once again Descartes has partitioned claims based on the understanding into two classes, those that can be called into doubt, and those which quite simply cannot.

The truths of mathematics
These can now be called into doubt -- they might all be false.
2 + 2 = 4
Truths which cannot fail to be true

I think, therefore I exist
Truths derived from the understanding

Descartes' achievement in isolating a truth he cannot doubt by use of this method is to defeat the universal skeptical claims that nothing is known except that one knows nothing, the claim of the Academic skeptic. It also defeats the claim that nothing is known and one does not even know that, the claim of the Pyhronian skeptic. As one can imagine, philosophers have raised various objections to this claim to certainty. At this point, however, it is simply worth pausing to admire Descartes' cleverness in defeating the skeptics.

Still, to defeat such universal skepticism, while an admirable achievement, is the easiest objective. For one need find only one or two truths which can be known for certain to defeat universal skepticism. This is hardly the end of skepticism, however, since many other more limited skeptical arguments remain to be defeated. So you know that you exist and are a thinking thing. If you can still doubt that God does not exist, that 17 + 8 = 25, that the moon exists some two hundred thousand miles from Earth, you have not gotten very far with skepticism. Still, Descartes is quite optimistic. He says: "Archimedes required only one fixed and immovable point to move the whole world from its place, and I too can hope for great things if I can find even one small thing which is certain and indubitable!" (Pg.6) Descartes has now achieved that goal. In the next unit, we will see how Descartes tries to make progress beyond the bare knowledge that he exists!


BACK   6 of 6   NEXT