George Berkeley was one of the three most famous British Empiricists. (The other two are John Locke and David Hume.) Berkeley is best known for his early works on vision (An Essay towards a New Theory of Vision, 1709) and metaphysics (A Treatise concerning the Principles of Human Knowledge, 1710; Three Dialogues between Hylas and Philonous, 1713).
Berkeley’s empirical theory of vision challenged the then-standard account of distance vision, an account which requires tacit geometrical calculations. His alternative account focuses on visual and tactual objects. Berkeley argues that the visual perception of distance is explained by the correlation of ideas of sight and touch. This associative approach does away with appeals to geometrical calculation while explaining monocular vision and the moon illusion, anomalies that had plagued the geometric account.
Berkeley claimed that abstract ideas are the source of all philosophical perplexity and illusion. In his Introduction to the Principles of Human Knowledge he argued that, as Locke described abstract ideas (Berkeley considered Locke’s the best account of abstraction), (1) they cannot, in fact, be formed, (2) they are not needed for communication or knowledge, and (3) they are inconsistent and therefore inconceivable.
In the Principles and the Three Dialogues Berkeley defends two metaphysical theses: idealism (the claim that everything that exists either is a mind or depends on a mind for its existence) and immaterialism (the claim that matter does not exist). His contention that all physical objects are composed of ideas is encapsulated in his motto esse is percipi (to be is to be perceived).
Although Berkeley’s early works were idealistic, he says little in them regarding the nature of one’s knowledge of the mind. Much of what can be gleaned regarding Berkeley’s account of mind is derived from the remarks on “notions” that were added to the 1734 editions of the Principles and the Three Dialogues.
Berkeley was a priest of the Church of Ireland. In the 1720s, his religious interests came to the fore. He was named Dean of Derry in 1724. He attempted to found a college in Bermuda, spending several years in Rhode Island waiting for the British government to provide the funding it had promised. When it became clear that the funding would not be provided, he returned to London. There he published Alciphron (a defense of Christianity), criticisms of Newton’s theory of infinitesimals, The Theory of Vision Vindicated, and revised editions of the Principles, and the Three Dialogues. He was named Bishop of Cloyne in 1734 and lived in Cloyne until his retirement in 1752. He was a good bishop, seeking the welfare of Protestants and Catholics alike. His Querist(1735-1737) presents arguments for the reform of the Irish economy. His last philosophical work, Siris (1744), includes a discussion of the medicinal virtues of tar water, followed by properly philosophical discussions that many scholars see as a departure from his earlier idealism.