Wednesday, April 23, 2008

Descartes, skepticism, and Bouwsma

Our reading of the Meditations suggests that Descartes's intellectually courageous strategy for refuting skepticsm ultimately fails. He begins by giving skepticism everything it could ask for, up to and including an evil genius, and then attempts to refute it through the application of clear and distinct reasoning to the cogito, the necessary existence of God, and the consequent knowability of the material world. The cogito is his Archimedean point, and God serves as lever by means of which he thinks he can, with care and difficulty, know the world. As we have seen, however, clarity and distinctness are slipperier than they appear, the arguments for God are dubious at best, and the skeptic is far from vanquished. Moreover, along the way Descartes's method yields an invidious and unsustainable metaphysical distinction between mind and body, of which we are justly skeptical.

So has the skeptic won the day? It seems that if like Descartes we grant the skeptic the most extreme hypothetical possibilities for being misled, including an evil genius, we forfeit the possibility of knowledge (whether apodictically certain or even probable). But is such an evil genius actually conceivable? Bouwsma tells a compelling story about why it is not, that the skeptic is not entitled to worry about global deception by an all-powerful deceiver, even as an abstract possibility. If Bouwsma is correct, then Descartes need not have yielded so much ground to the skeptic in the first place.

Thursday, April 3, 2008

The Tortoise and Achilles

Here is a link to a famous dialogue by Lewis Caroll (aka E.R. Dodson, Cambridge logician and mathematician). I read it as a comic but graphic example of the ultimate undefeatability of a certain sort of skepticism.

Wednesday, April 2, 2008

Landesman's twelfth chapter nicely poses the impasse between Moore and the Skeptic. It becomes clear that the difficulty of adjudicating the dispute turns on the ambiguity of the ground-rules: On whom should the burden of proof fall? Must Moore prove that he knows his premise, here are two hands, or must the Skeptic prove that he does not know it?

By analogy, consider a court of law. A criminal defendant is not required to prove her innocence; rather the prosecution must show, beyond reasonable doubt, that the defendant is guilty, otherwise she goes free. But our problem is compounded. Not only must we determine in advance (and in some principled way) whether Moore or the Skeptic plays the role of prosecutor or defendant, we must determine whether this is a criminal, a civil, or some other kind of trial, and who precisely is qualified to sit on the jury. In a civil trial the prosecutor (or more properly plaintiff) must merely convince the jury that a preponderance of evidence, more than half of it, is against the defendant. The criminal standard is beyond reasonable doubt, meaning all but completely certain. Perhaps what we could call an epistemic trial demands a still higher standard, that of no possible doubt.

Perhaps we can stretch this metaphor, considering the alternative burdens and standards of proof, and find some clarity about the matter.