I.2 Overview of the Book's Themes
I.19 We begin the book by discussing an ancient puzzle: the Regress Problem. The Regress Problem has to do in the main with the justification of belief. Recall from our discussion in Section I.1 of the nature of knowledge that most epistemologists think that knowing a proposition has to involve something in addition to simply believing a proposition that turns out to be true. (If knowledge didn't require this, there'd be no clear difference between knowledge and lucky guesses.) The idea we noted in passing is that knowing a proposition requires (at least) possessing a justified true belief where justification (of the sort relevant to knowledge, as opposed to, say, moral goodness) means something like being “backed by good reasons.” The Regress Problem takes this idea as a starting point and then shows how things can get very awkward very quickly. Just suppose, for example, that a given belief is justified only if it is supported by further beliefs. Now here's a question: must these further beliefs themselves be justified? If not, it's hard to see how the original belief would be justified. But if so, then they too must be backed by good reasons. Taking this idea to its logical conclusion indicates (bizarrely) that a belief is justified only if it's backed by an infinite number of good reasons – something it's not obvious that we actually have. Once this puzzle is set out, various solutions to it are canvassed: coherentism, infinitism, and foundationalism. As we'll see, foundationalism is shown to have certain advantages over the other two options.
I.20 On the foundationalist view, some justified beliefs are justified without requiring support from further beliefs. In some cases, as the foundationalist has it, perceptual experiences (e.g. your seeing a table in front of you) suffice to play the justification‐conferring role for some non‐inferential justified beliefs (i.e. beliefs that are both justified but not based on other justified beliefs). But does perceptual experience really have what it takes to stop the regress of justification? If so, how, exactly, does that work? Chapter 2 tries to get a grip on these issues. In the course of doing so, we delve into the matter of what kind of a thing perceptual experience is, and how the nature of perceptual experience connects to the matter of whether and how it can provide us with reasons for believing things.
I.21 Even if it turns out that perceptual experiences really are good enough to stop the regress and thus to justify beliefs non‐inferentially, it is worth asking whether that anything that justifies a justified belief must derive in some way from experience – for example, perceptual, introspective, or otherwise. The matter of whether (and if so, why; if not, why not) the answer is “yes” or “no” will be the guiding topic explored in Chapter 3, and it's one that has been divisive in epistemology from the early‐modern period onward. Proponents of a priori justification allow that at least some beliefs may be non‐experientially justified – that is, that they are such that the source of their justification is, in some relevant way, independent of experience. Beliefs whose justification (non‐trivially) derives from experience are justified a posteriori. The question of whether all justified beliefs are justified a posteriori (and whether some might be justified a priori) has marked a long‐standing distinction in philosophy between two epistemological traditions: rationalism and empiricism. Chapter 3 aims at giving readers a grounding in this.
I.22 In Chapter 4, we explore ways of using reasoning to gaining new justified beliefs and knowledge from the ones we have. It should be unsurprising that we can't gain new justified beliefs through bad reasoning (even if the beliefs bad reasoning generates happen sometimes to be true). But just how good does the reasoning have to be, exactly? At one end of the spectrum, we might think that the kind of reasoning that's needed to get us from one justified belief to another must be conditionally infallible; a given inference rule is conditionally infallible if it's impossible to reason in accordance with the rule to a mistaken belief if all of the beliefs you reason from are correct. We canvass some worries for both the necessity and sufficiency of conditionally infallible rules for extending our justification and knowledge; in the course of doing so, we engage with (among other things) deductive and inductive reasoning, Hume's problem of induction, and closure principles.
I.23 As we noted in Section I.1, epistemologists are interested in knowledge, and not merely in justification. While Chapters 1–4 concern mostly issues to do with epistemic justification (with some cursory discussions of propositional knowledge), Chapter 5 looks knowledge square in the face. In particular, Chapter 5 concerns the nature of knowledge. Recall from Section I.1 the view that knowledge = justified, true belief:
K=JTB: you know that p iff (i) p is true, (ii) you believe p, and (iii) you are justified in so believing.
As we noted, the JTB view of knowledge is no good because knowledge requires something in addition to JTB. Chapter 5 explains why this is, and introduces what are called “Gettier cases” – cases that show, pretty darn convincingly, that a person could have a justified true belief that p but still fail to know that p. What these Gettier cases suggest is that we need to figure out what else knowledge requires. Three conditions that have been proposed for dealing with Gettier cases are a causal condition, a modal condition, and an ability or virtue condition. We discuss the prospects of all three; in light of some of the problems with each, we also outline a less optimistic idea: that perhaps it was a mistake to initially attempt to provide a non‐circular informative analysis of knowledge in terms of its constituent parts.
I.24 Chapters 6 and 7 concern two sources of knowledge beyond perception: memory and testimony. These are both very important. Much of what we believe is on the basis of what others (friends, teachers, experts, etc.) tell us; and without memory we wouldn't believe or know anything we do (perceptual, testimonial, or otherwise) for long enough to act on it successfully. In Chapter 6, which concerns memory, we explore in some detail the connection between two kinds of memory, episodic and factual, and their roles in the justification of belief and retention of knowledge. In the course of doing so, we consider a number of competing views concerning the role that apparent memories play in the justification of belief. These debates interact with issues that matter for the proper formulation of foundationalism and to the internalism–externalism debate, to which we'll return in Chapter 9. One important issue that arises in connection to discussions of all potential sources of knowledge and of justification has to do with the possibility of justifying our reliance on sources. The case of memory shows in a particularly clear way the difficulty of justifying our reliance on a source, and this matters to skeptical challenges to our