ABSTRACT
This chapter considers Berkeley’s positive arguments for idealism and his criticism of John Locke. It might be argued that ‘idea’ in Locke’s day had the narrower meaning of being an image, but this is no defence of Berkeley. Berkeley has three main arguments to support his idealism: an argument from common sense; an a priori argument, which he takes to be the central one; and an argument based on the impossibility of matter causing ideas. Berkeley’s argument is a reduction to absurdity: the realist hypothesis implies a contradiction and so is false. Given the truth of idealism and that the rocks and craters on the moon are real, some spirit must have the ideas that compose them and this spirit is God, according to Berkeley. To be an empiricist is to hold that experience is the only source of justification of claims of real existence, and leaves the explicit definition of ‘real existence’ to metaphysics.
