10 - What does it take to “have” a reason?

Summary

If I believe, for no good reason, that P and I infer (correctly) from this that Q, I don't think we want to say that I “have” P as evidence for Q. Only things that I believe (or could believe) rationally, or perhaps, with justification, count as part of the evidence that I have. It seems to me that this is a good reason to include an epistemic acceptability constraint on evidence possessed.

It is a truism that adopting an unjustified belief does not put you in a better evidential position with respect to believing its consequences. This truism has led many philosophers to assume that there must, at a minimum, be a justification condition (or perhaps a knowledge condition) on what it takes to count as having evidence. This is the best (or only) possible explanation of the truism, these philosophers have believed. This chapter explores an alternative explanation for the truism. According to the alternative explanation, unjustified beliefs do not put you in a better evidential position with respect to believing their consequences because evidence you have in virtue of having an unjustified belief is guaranteed to be defeated. Since lack of justification for a belief guarantees its defeat, I will suggest, we don't need to postulate a special justification condition (much less a knowledge condition) on what it takes to count as having evidence.