The Principles, published when the author was only twenty-six, is the most systematic of all of Berkeley's expositions of his theory of knowledge: it was the direct outgrowth of the Essay Towards a New Theory of Vision (1709), which sought to ban­ish the metaphysical abstractions of Absolute Space and Extension from philosophy, and was itself mainly concerned with the aboli­tion of Abstract Matter and of the ontological and theological corollaries of that concept. The Dialogues treat of substantially the same subjects but are more familiar and elegant in form and are devoted in the main to the refutation of the most plausible popular and philosophical objections to the new doctrine. The two books mark a distinctively new epoch in philosophy and science, and together afford a comprehensive survey of Berkeley's doctrines, placing within the reach of every reader in remarkably brief compass opinions which have profoundly influenced the course of intellectual history. Works of this kind have been almost invariably distinguished by their brevity, ""I had no inclinations is Berkeley's characteristic remark, ""to trouble the world with large volumes