Berkeley was the eldest son of William Berkeley, described as a “gentleman” in George's matriculation entry, and as a commissioned officer, a cornet of dragoons, in the entry of a younger brother. Brought up at Dysert Castle, Berkeley entered Kilkenny College in 1696 and Trinity College, Dublin, in 1700, where he was graduated with a B.A. degree in 1704. While awaiting a fellowship vacancy, he made a critical study of time, vision, and the hypothesis that there is no material substance. The principal influences upon his thinking were Empiricism, represented by the English philosopher John Locke, and Continental Skepticism, represented by Nicolas Malebranche and Pierre Bayle. His first publication, Arithmetica and Miscellanea Mathematica (published together in 1707), was probably a fellowship thesis.

Elected fellow of Trinity College in 1707, Berkeley began to “examine and revise” his “first arguings” in his revision notebooks. The revision was drastic and its results revolutionary. His old principle was largely superseded by his new principle; i.e., his original line of argument (epistemology) for immaterialism, based on the subjectivity (Idealism) of colour, taste, and the other sensible (realism) qualities, was replaced by a simple, profound analysis of the meaning of “to be” or “to exist.” “To be,” said of the object, means to be perceived; “to be,” said of the subject, means to perceive.

Berkeley called attention to the whole situation that exists when a person perceives something, or imagines it. He argued that, when a person imagines trees or books “and no body by to perceive them,” he is failing to appreciate the whole situation: he is “omitting” the perceiver, for imagined trees or books are necessarily imagined as perceivable. The situation for him is a two-term relation of perceiver and perceived; there is no third term; there is no “idea of ” the object, coming between perceiver and perceived.

The revision was a gradual development. At the start Berkeley held that nothing exists but “conscious things.” “On second thoughts,” he was certain of the existence of bodies and knew intuitively “the existence of other things besides ourselves.” His expressions, “in the mind” and “without the mind,” must be understood accordingly. As he wrote in his notebook, heat and colour (which philosophers had classed as secondary qualities because of their supposed subjectivity) are “as much without the mind” as figure and motion (classed as primary qualities) or as time; for both primary and secondary qualities are so in the mind as to be in the thing, and are so in the thing as to be in the mind. The mind does not become red, blue, or extended when those qualities are in it; they are not modes or attributes of mind. Colour and extension are not mental qualities for Berkeley: colour can be seen, and extension can be touched; they are “sensible ideas,” or sense-data, the direct objects of percipient mind.

Berkeley accepted possible perception as well as actual perception; i.e., he accepted the existence of what a person is not actually perceiving but might perceive if he took the appropriate steps. The opposite view was held by some philosophers, including Materialists (Materialism), who (in Berkeley's words) “are by their own principles forced” to accept it. They are forced to accept that objects actually seen and touched have only an intermittent existence, that they come into existence when perceived and pass into nothingness when no longer perceived. Berkeley treated those views with respect; he denied that they are absurd; but he did not hold them, and he explicitly denied that they follow from his principles. In effect he said to his readers, “You may hold, if you will, that objects of sense have only an ‘in-and-out' existence, that they are created and annihilated with every turn of man's attention; but do not father those views on me. I do not hold them.” In his notebook he wrote, “Existence is percipi or percipere. The horse is in the stable, the Books are in the study as before.” Horse and books, when not being actually perceived by man, are still there, still perceivable “still with relation to perception.” To a nonphilosophical friend Berkeley wrote, “I question not the existence of anything that we perceive by our senses.”

Berkeley's immaterialism is open to “gross misinterpretation,” as he said in his preface; rightly understood, it is common sense. Like most people, he accepted and built on “two heads,” “two kinds entirely distinct and heterogeneous”: (1) active mind or spirit, perceiving, thinking, and willing; and (2) passive objects of mind, viz., sensible ideas (sense-data) or imaginable ideas.

Berkeley's golden period of authorship followed the revision. In An Essay Towards a New Theory of Vision (1709), he examined visual distance, magnitude, position, and problems of sight and touch, and concluded that “the proper (or real) objects of sight” are not without the mind, though “the contrary be supposed true of tangible objects.” In his Treatise Concerning the Principles of Human Knowledge, Part I (1710), he brought all objects of sense, including tangibles, within the mind; he rejected material substance, material causes, and abstract general ideas; he affirmed spiritual substance; and he answered many objections to his theory and drew the consequences, theological and epistemological. His Three Dialogues between Hylas and Philonous (1713), by its attractive literary form and its avoidance of technicalities, reinforced the main argument of the Principles; the two books speak with one voice about immaterialism.

Berkeley was made a deacon in 1709 and ordained a priest in 1710. He held his fellowship for 17 years, acting as librarian (1709), junior dean (1710–11), and tutor and lecturer in divinity, Greek, and Hebrew.

In politics Berkeley was a Hanoverian Tory, and he defended the ethics of that position in three sermons, published as Passive Obedience (1712). Thus, with four major books in five years, the foundations of his fame were laid; and, when he first left Ireland in 1713 on a leave of absence, he was already a man of mark in the learned world; his books were reviewed on the Continent, and Gottfried Wilhelm Leibniz, the wide-ranging author of the Monadology, knew of his immaterialism and commented upon it.

Among the London wits he was an immediate success. Jonathan Swift, dean of St. Patrick's Cathedral, Dublin, presented him at court. For Sir Richard Steele, an essayist, he wrote essays in The Guardian against the freethinkers. He was in the theatre with Joseph Addison, essayist and poet, on the first night of Cato and has left a spirited description of the experience. Alexander Pope credited him with “ev'ry virtue under heav'n.” In 1713–14 he went on an embassy to Sicily as chaplain with Charles Mordaunt, 3rd earl of Peterborough, whom Berkeley called an “ambassador extraordinary.” In 1715 during the Jacobite rebellion (on behalf of the exiled Stuarts) he proved his loyalty by publishing his Advice to the Tories Who Have Taken the Oaths. He was abroad again from 1716 to 1720 in Italy, acting as tutor to George Ashe, son of the Bishop of Clogher (later, of Derry); his four travel diaries give vivid pictures of sightseeing in Rome and of tours in southern Italy. On his return he published his De motu (1721), which rejected Sir Isaac Newton's absolute space, time, and motion, gave a veiled hint of his immaterialism, and has recently earned him the title “precursor of Mach and Einstein.”

Resuming his work in Dublin, he took a full part in teaching and administration for more than three years. In 1724 he was appointed dean of Derry, and his 24 years' connection with Trinity College ended.

His American venture and ensuing years. The deanery and legacy from Hester van Homrigh (Swift's Vanessa) were seen by Berkeley as providences, furthering his “scheme of Bermuda,” in the New World. The frenzied speculation that preceded the bursting of the South Sea Bubble had shaken his faith in the Old World, and he looked in hope to the New. His Essay Towards preventing the Ruin of Great-Britain (1721) was soon succeeded by his prophetic verses on “Westward the course of empire takes its way.” Already by 1722 he had resolved to build a college in Bermuda for the education of young Americans (Indians), publishing the plan in A Proposal For the better Supplying of Churches . . . (1724). The scheme caught the public imagination; the King granted a charter; the Archbishop of Canterbury acted as trustee; subscriptions poured in; and Parliament passed a contingent grant of £20,000. But there was opposition; an alternative charity for Georgia was mooted; and the prime minister, Sir Robert Walpole, hesitated.

In 1728 Berkeley married Anne, daughter of Chief Justice Forster, a talented and well-educated woman, who defended her husband's philosophy after his death. Soon after the wedding, they sailed for America, settling at Newport, R.I., where Berkeley bought land, built a house (Whitehall), and waited. Berkeley preached often in Newport and its neighbourhood, and a philosophical study group met at Whitehall. Eventually, word came that the grant would not be paid, and Berkeley returned to London in October 1731. Several American universities, Yale in particular, benefitted by Berkeley's visit; and his correspondence with Samuel Johnson, later president of King's College (Columbia University), is of philosophical importance.

Alciphron; or, The Minute Philosopher (1732) was written at Newport, and the setting of the dialogues reflects local scenes and scenery. It is a massive defense of theism and Christianity with attacks on deists and freethinkers and discussions of visual language and analogical knowledge and of the functions of words in religious argument.

Upon his return to London in 1731, Berkeley's pen, never idle for long, became active. A writer in the Daily Post-boy commended Alciphron but attacked the appended Essay on vision. Berkeley replied with The Theory of Vision, or Visual Language . . . Vindicated and Explained (1733). This fine work brought the metaphysics (theory of being) of the Essay into line with the Principles and added his doctrine of cause, admitting defects in the premises of the original Essay. Alciphron provoked replies from the satirist Bernard de Mandeville; John Hervey, Baron Hervey of Ickworth; the statesman Henry St. John, 1st Viscount Bolingbroke; and Peter Browne, Berkeley's former teacher and provost. To Browne, Berkeley sent a long, private letter on analogy—first published in Mind (July 1969)—which constitutes an important supplement to his 4th dialogue.

In 1734 Berkeley published The Analyst; or, a Discourse Addressed to an Infidel Mathematician, which Florian Cajori (Cajori, Florian), a historian of mathematics, has called “the most spectacular event of the century in the history of British mathematics.” Besides being a contribution to mathematics, it was an argument ad hominem for religion. “He who can digest a second or third fluxion,” wrote Berkeley, “need not, methinks, be squeamish about any point in divinity.” A long and fruitful controversy followed. James Jurin, a Cambridge physician and scientist, John Walton of Dublin, and Colin Maclaurin (Maclaurin, Colin), a Scottish mathematician, took part. Berkeley answered Jurin in his lively satire A Defence of Free-Thinking in Mathematics (1735) and answered Walton in an appendix to that work and again in his Reasons For Not Replying (1735).

Berkeley was consecrated as bishop of Cloyne in Dublin in 1734. He found Trinity College flourishing: its new library was completed, and John Stearne's Doric printing house was being built. To the latter, Berkeley contributed a font of Greek type and also founded the Berkeley gold medal for Greek. His episcopate, as such, was uneventful. He took a seat in the Irish House of Lords in 1737 and, while in Dublin, published A Discourse Addressed to Magistrates and Men in Authority (1738), condemning the Blasters whose Hell-Fire Club, now in ruins, still can be seen near Dublin.

The see-house at Cloyne was a cultured home and a social centre and, during epidemics, a dispensary. On arrival, the family consisted of his wife and two sons; and two more sons and two daughters were born at Cloyne.

In 1745 Berkeley addressed open letters to his clergy and to the Roman Catholics of his diocese about the Stuart uprising. In letters to the press over his own name or through a friend, he expressed himself on several public questions, political, social, and scientific. Two major works stand out, The Querist and Siris. The Querist, published in three parts from 1735 to 1737, deals with basic economics—credit, demand, industry, and “the true idea of money”—and with special problems, such as banking, currency, luxury, and the wool trade. The final query puts the central question, “Whose fault is it if poor Ireland still continues poor?”

Siris (1744) passed through some six editions in six months. It is at once a treatise on the medicinal virtues of tar-water, its making and dosage, and a philosopher's vision of a chain of being, “a gradual evolution or ascent” from the world of sense to “the mind, her acts and faculties” and, thence, to the supernatural and God, the three in one.

In August 1752, Berkeley commissioned his brother, Dr. Robert Berkeley, as vicar-general and arranged with the bishop of Cork as to his episcopal duties and, with his wife and his children George and Julia, went to Oxford and took a house in Holywell Street, where he resided until his death. He was buried in Christ Church Chapel.