George Berkeley

George Berkeley (1685–1753), Anglo-Irish philosopher and Bishop of Cloyne, developed the metaphysical system known as immaterialism or subjective idealism, encapsulated in the dictum esse est percipi (to be is to be perceived). Educated at Trinity College Dublin, he published his major philosophical works in his twenties: An Essay towards a New Theory of Vision (1709), A Treatise concerning the Principles of Human Knowledge (1710), and Three Dialogues between Hylas and Philonous (1713). Berkeley argued that matter, conceived as mind-independent substance, is incoherent; what exist are minds (spirits) and their ideas. The orderly persistence of the sensible world requires a universal perceiver—God—whose continuous perception sustains reality. This makes his idealism a vehicle for natural theology: the existence and reliability of the natural order is direct evidence of an omnipresent divine mind. In Alciphron (1732), composed during his stay in Rhode Island, he defended Christianity against freethinkers such as Shaftesbury, Mandeville, and the deists, addressing religious language, moral motivation, and the design argument. His later Siris (1744) joined medical, scientific, and Neoplatonic concerns. Berkeley was sharply criticized by contemporaries who charged him with skepticism or with collapsing the external world; Samuel Johnson's stone-kicking refutation became proverbial. Hume engaged his arguments critically, while Kant distinguished his own transcendental idealism from Berkeley's. His theistic immaterialism remains a touchstone in debates on perception, idealism, and arguments from the conditions of experience to God.