Experience and the limits of understanding › Legacy and Connections

A useful next step is to compare Locke's positive account with Berkeley's objections. Begin with two questions: can an abstract idea function as Locke describes, and can an idea resemble something that is not itself an idea? Berkeley raises both problems in the *Principles*. Berkeley also disputes the separation between primary and secondary qualities. In sections 9–15 of the *Principles*, he challenges attempts to treat extension, figure, and motion as existing independently of perception while treating colors and tastes differently. This is a criticism of Locke's distinction, rather than a conclusion Locke himself accepts. Return then to Locke's own four-book sequence. A claim about where ideas originate is different from a claim about what a word means; both differ from the question of whether a proposition counts as knowledge. Keeping those questions apart makes it easier to see which part of Locke's account a criticism actually targets. The *Essay* rewards that slower reading. Its blank-paper image opens the discussion; the account of mental operations, language, and degrees of knowledge supplies the qualifications. The image should lead us into those distinctions instead of replacing them.