Abstract: This book is an interpretation of Berkeley's immaterialism or ‘idealism’: an exposition of his arguments, an assessment of their significance, and an explanation (inevitably partial) of their content and form. In the first five chapters, I explore a range of themes that seem, on the surface, to be distant from Berkeley's denial of matter or material substance: his account of intentionality; his attack on abstract ideas; his repudiation of simple ideas; his affirmation of objective necessity; and his appeal to intelligibility in understanding cause and effect relations. In Ch. 6, I show how Berkeley's consideration of these themes shaped his defence of immaterialism. In the final three chapters, I examine some of the consequences of immaterialism and the challenges confronting it: the existence of unperceived objects; the success of modern corpuscularian science; and the nature and existence of mind or spiritual substance.

Keywords: Berkeley, causation, corpuscularianism, History of philosophy, idealism, ideas, immaterialism, intelligible, intentionality, matter, mind, necessity, perception, substance