(born March 12, 1685, near Dysert Castle, near Thomastown?, County Kilkenny, Ire.died Jan. 14, 1753, Oxford, Eng.) Irish bishop, philosopher, and social activist. He worked principally at Trinity College, Dublin (to 1713), and as bishop of Cloyne (1734–52). He is best known for his contention that, for material objects, to be is to be perceived (Esse est percipi). His religious calling may have prompted his qualification that, even if no human perceives an object, God does, thereby ensuring the continued existence of the physical world when not perceived by any finite being. With John Locke and David Hume, he was one of the founders of modern empiricism. Unlike Locke, he did not believe that there exists any material substance external to the mind, but rather that objects exist only as collections of sensible ideas. His works include An Essay Towards a New Theory of Vision (1709), Treatise Concerning the Principles of Human Knowledge (1710), and Three Dialogues Between Hylas and Philonous (1713). He spent part of his career in America, where he advocated educating Native Americans and blacks. The city of Berkeley, Calif., U.S., is named for him.