In George Berkeley's two most important works, the Principles of Human Knowledge and Three Dialogues Between Hylas and Philonous, he argued that there is no such thing as matter: only minds and ideas exist, and physical things are nothing but collections of ideas. In defense of this idealism, he advanced a battery of challenging arguments purporting to show that the very notion of matter is self-contradictory or meaningless, and that even if it were possible for matter to exist, we could not know that it does; and he then put forward an alternative world-view that purported to refute both skepticism and atheism. Using the tools of contemporary analytic philosophy, Georges Dicker here examines both the destructive and the constructive sides of Berkeley's thought, against the background of the mainstream views that he rejected. Dicker's accessible and text-based analysis of Berkeley's arguments shows that the Principles and the Dialogues dovetail and complement each other in a seamless way, rather than being self-contained. Dicker's book avoids the incompleteness that results from studying just one of his two main works; instead, he treats the whole as a visionary response to the issues of modern philosophy- such as primary and secondary qualities, external-world skepticism, the substance-property relation, the causal roles of human agents and of God. In addition to relating Berkeley's work to his contemporaries, Dicker discusses work by today's top Berkeley scholars, and uses notions and distinctions forged by recent and contemporary analytic philosophers of perception. Berkeley's Idealism both advances Berkeley scholarship and serves as a useful guide for teachers and students.