On what we should believe (and when (and why) we should believe what we know we should not believe)

A theory of what we should believe should include a theory of what we should believe when we are uncertain about what we should believe and/or uncertain about the factors that determine what we should believe. This chapter presents a novel theory of what we should believe that gives externalists a way of responding to a suite of objections having to do with various kinds of error, ignorance, and uncertainty. This theory is inspired by recent work in ethical theory in which non-consequentialists ‘consequentialize’ their theories and then use the tools of decision-theory to give us an account of what we ought (in some derivative sense) to do when we’re uncertain about what we ought (in some primary sense) to do. Because what we ought to do is acquire knowledge and avoid ignorance, we (subjectively) ought to believe if the probability of being in a position to know is sufficiently high. This view has a number of important virtues. Among them, it gives us a unified story about how defeaters defeat, explains puzzling intuitions about the differences between lottery cases, preface cases, and cases of perceptual knowledge, and provides a general framework for thinking about subjective normativity.