George Berkeley

George Berkeley was an Irish philosopher and Anglican bishop of the early eighteenth century, best known for the claim that material objects do not exist independently of the minds that perceive them. His immaterialism, summed up in the Latin phrase esse est percipi, "to be is to be perceived", was meant as a defence of common sense and religion against scepticism and atheism. Together with John Locke and David Hume, he is usually counted among the great British empiricists, philosophers who held that all knowledge comes from experience.

Berkeley was born on 12 March 1685 at Dysart Castle, near Thomastown in County Kilkenny, in the south-east of Ireland, into a family of English descent belonging to the Protestant Anglo-Irish minority. He was educated at Kilkenny College and entered Trinity College, Dublin, at the age of fifteen. Trinity's curriculum was unusually modern for its day, and there he read the new science and philosophy of the late seventeenth century, above all Isaac Newton, René Descartes, Nicolas Malebranche and Locke. He graduated in 1704, became a fellow of the college in 1707 and was ordained in the Church of Ireland soon afterwards.

From 1707 he kept private notebooks, now known as the Philosophical Commentaries, in which he worked out his ideas in short numbered entries. They show his immaterialism taking shape as a reaction against Locke and Descartes. In his twenties he published the books on which his fame rests: 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), a more popular restatement of the Principles in dialogue form.

Berkeley's starting point was Locke's view that the mind directly perceives only its own ideas, and that these ideas represent material things outside it. Berkeley argued that this picture leads straight to scepticism: if all we ever meet are ideas, we can never check whether they resemble the hidden material objects supposed to cause them. Worse, he thought the notion of matter was empty. Locke had distinguished primary qualities, such as shape and motion, which really belong to objects, from secondary qualities, such as colour and taste, which exist only in the perceiver. Berkeley replied that the two cannot be separated: no one can conceive a shape that has no colour, and so primary qualities are as mind-dependent as secondary ones.

His conclusion was that the things we see and touch, tables, trees and houses, simply are collections of ideas, and that their being consists in being perceived. Only minds, which he called spirits, and their ideas exist. This did not mean, he insisted, that a tree vanishes when no one looks at it. Our ideas of sense are not under our control, unlike the ideas of imagination, so something else must cause them. That cause is God, an infinite mind who produces the orderly sequence of ideas we call nature and in whose mind things continue to exist. The regularities studied by science are the rules by which God gives us our ideas. Berkeley thus believed that he had removed the grounds for scepticism and materialist atheism at a stroke, while leaving the ordinary person's world exactly as it was.

The theory of vision supported this picture. Berkeley argued that we do not see distance directly; we learn to judge it by associating what we see with sensations of touch and movement. Sight, in his view, is a kind of language in which God speaks to us about what we may touch. The book was an important early contribution to the psychology of perception.

Berkeley's ideas were received at first with ridicule or incomprehension. He spent the years 1713 to 1720 largely abroad, in London, where he met writers such as Jonathan Swift, Alexander Pope and Richard Steele, and on two tours of the continent, the second as tutor to a young gentleman. On the way home in 1720 he wrote De Motu, an essay on the foundations of mechanics which treated Newton's forces as useful mathematical fictions rather than real things, a view later admired by philosophers of science such as Ernst Mach.

Appointed Dean of Derry in 1724, Berkeley conceived a scheme to found a college in Bermuda to train clergy for the British colonies and to educate Native Americans. Convinced that Europe was in moral decline and that the future lay in the New World, he obtained a royal charter and a promise of £20,000 from Parliament. In 1728 he sailed with his new wife, Anne Forster, to Newport, Rhode Island, to wait for the money, which never came. While there he bought a farm, Whitehall, and owned enslaved Africans who worked on it, a fact that has drawn renewed attention in recent years. In 1731 he gave up the project and returned to Britain, leaving his farm and books to Yale College. In America he wrote Alciphron (1732), a defence of Christianity against the freethinkers of the day.

Back in London, Berkeley published The Analyst (1734), a sharp critique of the logical foundations of Newton's calculus, which argued that its infinitesimals, quantities treated as both something and nothing, were no clearer than the mysteries of religion that mathematicians mocked. The objection was taken seriously and helped push mathematicians towards more rigorous foundations.

In 1734 he became Bishop of Cloyne in County Cork and spent most of the rest of his life there. Ireland's poverty concerned him, and in The Querist (1735–1737), written entirely as a series of questions, he proposed a national bank and paper currency and asked why a fertile country should have so many hungry people. During an epidemic in the early 1740s he became an enthusiastic advocate of tar-water, a medicine made by steeping pine tar in water. His Siris (1744) moved from its supposed virtues to speculation about the nature of the universe and God, and was his best-selling book in his lifetime. In 1752 he moved to Oxford, where his son was studying, and he died there on 14 January 1753. He is buried in Christ Church Cathedral.

Few of Berkeley's readers have accepted his immaterialism, and it was long treated as a famous paradox. Samuel Johnson is said to have kicked a stone and declared "I refute it thus", missing the point that Berkeley did not deny that stones feel solid. Yet his arguments against Locke's theory of representation proved hard to answer. Hume took over his criticism of abstract ideas and his doubts about matter, but turned them against Berkeley's own belief in a God and in spiritual substances. Immanuel Kant worked hard to distinguish his own transcendental idealism from Berkeley's. In the nineteenth and twentieth centuries his ideas influenced phenomenalists such as John Stuart Mill and the logical positivists, who also tried to reduce talk of physical objects to talk of experiences.

Berkeley is now regarded as one of the key figures of early modern philosophy, a sharp critic of the new science's assumptions as well as of its mathematics. The University of California's Berkeley campus and the city around it were named after him in the 1860s, inspired by a line from his poem on the prospect of planting learning in America. In 2023 Trinity College Dublin removed his name from the library that had been called after him, citing his ownership of enslaved people and his defence of slavery.