A Puzzle About the Significance of Skepticism

William S. Larkin

Society for Skeptical Studies: 3-26-04

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I. Moorean Background

A. Common Sense Propositions

B. Self-Defeating Skeptic

C. Turning the Skeptic’s Argument on its Head

D. Philosophy, Common Sense, and Analysis

II. Introduction

A. The following claims are individually plausible:

1. Skepticism is philosophically significant.

2. Skepticism is philosophically significant only if there is some skeptical argument that is bound to reveal something about either the scope or the nature of knowledge.

3. Any skeptical argument can be put into the following form:

(SK) P1: If S knows that P, then N.

P2: Not-N.

C: So S does not know that P.

B. My Thesis: The above claims are jointly inconsistent.

1. If all three claims are true, then some SK argument is bound to reveal something about either the scope or nature of knowledge.

2. Some SK argument is bound to reveal something about either the scope or nature of knowledge only if it is both dangerous and structurally compelling.

a. An SK argument is dangerous iff P ranges over some common sense propositions—ones that we ordinarily and naturally (and perhaps, unavoidably) take ourselves to know.

b. An argument is structurally compelling iff resisting the conclusion requires rejecting one of the premises.

3. No SK argument can be both dangerous and structurally compelling.

III. Argument

A. Main

P1: If some SK argument is dangerous, then it is either self-defeating or question begging.

1a: The first premise of any dangerous SK argument is justified either bottom-up or top-down.

1b: If it is justified bottom-up, then the argument is self-defeating.

1c: If it is justified top-down, then the argument begs the question.

P2: If an SK argument is either self-defeating or question begging, then it is not structurally compelling.

C: So if some SK argument is dangerous, then it is not structurally compelling.

B. For 1b

1. If the first premise of a dangerous SK argument is justified bottom-up, then that premise presupposes that some common sense proposition P is an object of knowledge.

2. If the SK argument in question is dangerous, then its conclusion implies that P is not an object of knowledge.

C. For 1c

1. If the first premise (P1) of a dangerous SK argument is justified top-down, then it is a theoretical/philosophical claim.

2. If the SK argument in question is dangerous, then the negation of its conclusion (~C) is an ordinary/common sense claim.

3. If P1 is theoretical but ~C is ordinary, then SK can be successfully Moore-shifted—i.e., MS is at least as plausible as SK.

MS: (P2 & ~C) ® ~P1

SK: (P1 & P2) ® C

4. If SK can be successfully Moore-shifted, then it begs the question. No one will accept P1 (given P2) without first rejecting ~C—i.e., without first accepting C.

IV. Objections and Replies

A. Cartesian

1. Objection

a. Reflective philosophical claims are more epistemically secure than ordinary common sense claims.

b. So, in top-down situation, P1 is more epistemically secure than ~C.

c. So, in top-down situation, MS is not as plausible as SK

2. Reply

a. Claiming that reflective philosophical claims are more epistemically secure begs the question.

b. For it presumes that there is some reason to doubt ordinary common sense claims.

c. But that is just what skeptical argument is supposed to provide.

B. Contextualist

1. Objection

a. In top-down situation, we enter into a philosophical context with relatively high epistemic standards.

b. In a context with relatively high epistemic standards P1 is more epistemically secure than ~C.

c. So, in top-down situation, MS is not as plausible as SK.

2. Reply

a. The move from claiming P1 is more secure than ~C to that MS is not as plausible as SK begs the question.

b. For it presumes that a high-standard context is more appropriate when considering a skeptical argument.

c. But a high-standard context just is a context where ordinary common sense beliefs do not count as knowledge.

d. And so objection presumes just what skeptical argument designed to establish.