Principles Of Human Knowledge - Notes

Berkeley presents here the following argument (see Winkler 1989, 138):

(1) We perceive ordinary objects (houses, mountains, etc.).

(2) We perceive only ideas.

Therefore,

(3) Ordinary objects are ideas.

The argument is valid, and premise (1) looks hard to deny. What about premise (2)? Berkeley believes that this premise is accepted by all the modern philosophers. In the Principles, Berkeley is operating within the idea-theoretic tradition of the seventeenth and eighteenth centuries. In particular, Berkeley believes that some version of this premise is accepted by his main targets, the influential philosophers Descartes and Locke.

However, Berkeley recognizes that these philosophers have an obvious response available to this argument. This response blocks Berkeley's inference to (3) by distinguishing two sorts of perception, mediate and immediate. Thus, premises (1) and (2) are replaced by the claims that (1′) we mediately perceive ordinary objects, while (2′) we immediately perceive only ideas. From these claims, of course, no idealist conclusion follows. The response reflects a representationalist theory of perception, according to which we indirectly (mediately) perceive material things, by directly (immediately) perceiving ideas, which are mind-dependent items. The ideas represent external material objects, and thereby allow us to perceive them.