Epistemology

What it asks

Almost everyone believes a great many things. Very few of those beliefs were arrived at by a method anyone could describe. Epistemology begins by asking what would have to be added to a belief to make it knowledge — and by noticing that a belief can be true by luck, which does not feel like knowing at all.

The traditional answer, extracted from Plato's Theaetetus and repeated for two thousand years, is that knowledge is justified true belief: you know something if you believe it, it is true, and you have good reason for believing it. That definition survived until 1963, when Edmund Gettier published a three-page paper describing cases where all three conditions are met and it is still plainly not knowledge. The literature responding to those three pages is now enormous.

The recurring problems

Four problems recur.

Scepticism. If any of your beliefs could be false, how do you rule out the possibility that most of them are? The sceptical argument is easy to state and unreasonably hard to answer, and much of the branch consists of attempts.

The regress. A belief is justified by another belief, which needs justification in turn. Either the chain runs forever, or it circles, or it stops somewhere — and each option has a school built around defending it.

Sources. Perception, memory, testimony, reason and introspection all deliver beliefs. None of them is perfectly reliable, and they sometimes contradict each other.

The value question. Why is knowledge better than true belief? If the belief is true either way, the extra ingredient has to earn its keep.

How it developed

The questions are ancient; the name is not. Plato treated knowledge as the possession of an account, not merely a correct opinion. The sceptical schools of the Hellenistic world made the difficulty their whole subject. Descartes reopened it in the seventeenth century by doubting everything in order to find one thing that could not be doubted, and set the modern agenda in doing so: from then on the problem was how a mind gets outside itself to a world.

The empiricist answer — that knowledge is built from experience — and the rationalist answer — that some of it is not — divided the next two centuries. Kant's response, that the mind supplies the structure experience arrives in, reframed the dispute rather than settling it.

The twentieth century turned technical. Gettier's counterexamples broke the standard definition; reliabilism proposed that what matters is not the reasons a believer can give but whether the process producing the belief actually works; and the field split into competing repairs that are still being argued.

The positions within it

The rival answers within this branch belong to the Schools section rather than here. Empiricism and rationalism divide over the sources of knowledge; foundationalism, coherentism and infinitism over the regress; internalism and externalism over whether justification must be accessible to the believer. Pragmatism cuts across all of them by asking what the dispute is for.

Where it stands now

Two shifts define recent work. Social epistemology treats knowing as something communities do rather than individuals — testimony, expertise, disagreement and trust became central rather than peripheral. And formal epistemology brought probability into a field that had run on certainty, replacing the question of whether a belief is justified with the question of how confident it is reasonable to be.

Neither has retired the old problems. The sceptic has not been answered, only worked around.