It is important to try to understand Berkeley's exact position on what it is for someone to perceive an idea. He is frequently presented as holding that to perceive an idea is to be confronted by an object which is in some sense mind-dependent and private, and, if taken in a certain way, such a remark is not inaccurate. But the interpretation which renders it accurate needs to be specified and this is a task which awaits completion. Until it is completed, questions like ‘Can Berkeley account for everything we, as plain men, legitimately want to say?’, ‘Are his arguments against the possibility of mind-independent material substances sound?’, and ‘Is he right to hold that the ideas involved in different sense modalities are always different?’, cannot be finally resolved.

George Pitcher, in “Minds and Ideas in Berkeley”, makes a good start on the problem, but he does not consider a sufficient number of alternative analyses of ‘So and so perceives such and such an idea’. As a result he fails to pinpoint the exact analysis which Berkeley himself would favour.