Philosophy of Psychology

What it asks

Psychology explains behaviour by appeal to things nobody can see - beliefs, desires, memory, attention, intelligence, personality. Every one of those is inferred from what people do and say, and every one is defined partly by how it is measured.

So two questions run through everything. Are these real kinds, carving the mind at genuine joints, or useful summaries that could have been drawn otherwise? And what does a psychological explanation explain, given that a full neural story could in principle be told instead?

The recurring problems

Construct validity. A test measures something. Whether that something is the trait it is named after is a separate question, answered largely by more tests using the same assumptions. The circle is not vicious but it is not innocent either.

Levels of explanation. A behaviour can be explained by a reason, a cognitive process, or a neural mechanism. Whether these compete, complement each other, or reduce one to another determines what psychology is FOR, and there is no agreement.

Folk psychology. Ordinary explanation in terms of belief and desire is remarkably successful. Whether that success shows the categories are roughly right, or merely that they are useful, divides the field - and eliminative materialists argue that folk psychology is a false theory that mature science will replace.

Replication. A large proportion of published findings do not reproduce. That is a methodological crisis with philosophical content, because it exposes what was being assumed about evidence, publication and inference.

How it developed

Psychology separated from philosophy in the late nineteenth century, and the separation was never clean - introspection was its first method, and the objection that introspective reports are unverifiable is a philosophical one.

Behaviourism resolved the difficulty by restricting the subject matter to what could be observed. It produced real results and could not accommodate language, which is what ended it.

The cognitive revolution reinstated inner states as explanatory, on the model of information processing. Fodor's argument for modularity in 1983, that some mental systems are fast, automatic and sealed off from what one believes, gave the new framework a testable structure.

The Churchlands pressed the opposite case from 1981: that belief and desire belong to a folk theory as doomed as folk physics, and that neuroscience will not vindicate them but replace them. Few accept the conclusion; the argument has never been comfortably answered.

The replication crisis from around 2011 changed the field's self-understanding more than any argument, and made philosophy of psychology unusually practical.

The positions within it

Reductionism and explanatory pluralism; eliminative materialism; functionalism; modularity and its critics; behaviourism in its historical form. All are in the Schools section.

Where it stands now

Most of the live work is methodological rather than metaphysical: on measurement, on what a psychological construct is, on whether the field's statistical practice supports its claims.

That is an unusual position for a philosophy of science to be in, and a healthy one. The most-cited philosophical work in this area is now read by working psychologists, which is not true of most branches.