Skepticism, Externalism, and Closure

The skeptic challenges our ability to know (or justifiably believe) that the experience of seeming to remember on which we base our memory-claims is in fact a reliable guide to the past. How can we be sure that seeming memory experiences are representations of the past rather than, say, products of our imagination? As was shown in the previous chapter, skepticism about memory knowledge assumes internalism about justification. At the end of section 6.4, I suggested rejecting internalism and proposed an externalist response to skepticism about memory knowledge. The main aim of this chapter is to elaborate on the externalist response.

As was explained in section 6.1, internalism about justification is the view that all of the factors required for a belief to be justified must be accessible to the subject merely by reflecting and thus internal to his mind. Externalism about justification, on the other hand, is simply the denial of internalism, holding that some of the justifying factors may be external to the subject’s cognitive perspective. A belief is justified if it has the property of being truth-effective. No more than this is necessary for justification. Whether the subject takes his belief to be truth-effective doesn’t add anything to the belief’s epistemic status. Since externalism is the denial of internalism and since there is no third position besides internalism and externalism, any argument against internalism is an indirect argument for externalism. My arguments in favor of externalism about memory knowledge are, for the most part, indirect ones.

The most prominent recent externalist theories have been versions of reliabilism. While externalism is only a negative thesis consisting in the denial that justification and knowledge are completely internal, reliabilism is a positive thesis maintaining that what qualifies a belief as knowledge or as justified is its reliable linkage to the facts that make the belief true. The reliable linkage, which is commonly expressed by means of subjunctive conditionals, ensures that if the known proposition p were not true, the subject would not believe that p. Advocates of reliabilism argue that, a subject knows that p if he believes that p, p is true, and he would not believe that p unless p were true. The idea is that to know that p the belief must not be accidentally true. It must “track” or “indicate” the facts that make the belief true. The theory is externalist because it makes justification depend on factors that are not necessarily accessible to the knowing subject.