Berkeley's system, whatever may be the right textbook label to apply to it, was plainly a piece of religious apologetics, the outline of a constructive natural theology, of a theistic metaphysic. From the Principles onwards he was fashioning a reasoned case for the existence of God, of a certain kind of God with a certain kind of relation to the world.

Berkeley's introductory remarks to several of his treatises verify Jessop's evaluation. Berkeley saw his task to be the defence of the central tenets of classical theism, achieved through ‘a plain demonstration of the immediate Providence of an all-seeing God, and the natural immortality of the soul...’. At the foundation of this defence, as is well known, lies the metaphysic commonly called ‘immaterialism’, which holds that, contrary to popular belief, physical objects are not enduring material substances, but rather ideas inhering in finite and infinite spirit.