Epistemology Brownbag: Marc Alspector-Kelly

Date: February 12th, 2019

Time/Location: 12:30-2:00 in Kresge 3438

Title: The Skeptical Closure Argument

Abstract: Suppose that P is a piece of pedestrian knowledge (such as “I have hands”) and that SK is a skeptical hypothesis (such as “I’m a handless brain in a vat”). A much-discussed argument for skepticism—the skeptical closure argument, or SCA—runs as follows:

(1) You don’t know ~SK.

(2) If you don’t know ~SK then you don’t know P.

(3) So you don’t know P.

The skeptic appeals to (a common rendition of) knowledge closure in support of (2): if S knows P, and knows that P implies Q, then S knows Q. But I’ll show that (3) only follows from a much less plausible version of closure and that, if a more plausible version is substituted, the resulting argument threatens very few if any of our ordinary knowledge claims. I’ll then revise the SCA in such a way that it does mobilize a plausible closure principle while still threatening most ordinary knowledge. It turns out, however, that the needed support for the premises of the revised SCA either renders the argument dialectically superfluous or undermines closure itself. The overall result is that there is no plausible argument for skepticism that mobilizes closure. I’ll also indicate why a related skeptical argument—one that appeals to what I call “front-loading”—fares no better.