• Philosopher George Berkeley, 1685
  

In 1709, Berkeley published his first major work, An Essay towards a New Theory of Vision, in which he discussed the limitations of human vision and advanced the theory that the proper objects of sight are not material objects, but light and color. This foreshadowed his chief philosophical work A Treatise Concerning the Principles of Human Knowledge in 1710 which, after its poor reception, he rewrote in dialogue form and published under the title Three Dialogues between Hylas and Philonous in 1713.

In this book, Berkeley's views were represented by Philonous (Greek: 'lover of mind'), while Hylas (Greek: 'matter') embodies the Irish thinker’s opponents, in particular John Locke. Berkeley argued against Sir Isaac Newton's doctrine of absolute space, time and motion in De Motu (on Motion), published 1721. His arguments were a precursor to the views of Mach and Einstein. In 1732, he published Alciphron, a Christian apologetic against the free - thinkers, and in 1734, he published The Analyst, an empiricist critique of the foundations of infinitesimal calculus, which was influential in the development of mathematics.

His last major philosophical work, Siris (1744), begins by advocating the medicinal use of tar water, and then continues to discuss a wide range of topics including science, philosophy, and theology. Interest in Berkeley's work increased after World War II, because he tackled many of the issues of paramount interest to philosophy in the 20th century such as the problems of perception, the difference between primary and secondary qualities, and the importance of language.

Berkeley was born at his family home, Dysart Castle, near Thomastown, County Kilkenny, Ireland, the eldest son of William Berkeley, a cadet of the English noble family of Berkeley. He was educated at Kilkenny College and attended Trinity College, Dublin, completing a Master's degree in 1707. He remained at Trinity College after completion of his degree as a tutor and Greek lecturer.

His earliest publication was on mathematics, but the first that brought him notice was his Essay Towards a New Theory of Vision, first published in 1709. In the essay, Berkeley examines visual distance, magnitude, position and problems of sight and touch. While this work raised much controversy at the time, its conclusions are now accepted as an established part of the theory of optics.

The next publication to appear was the Treatise Concerning the Principles of Human Knowledge in 1710 which had great success and gave him a lasting reputation, though few accepted his theory that nothing exists outside the mind. This was followed in 1713 by Three Dialogues between Hylas and Philonous, in which he propounded his system of philosophy, the leading principle of which is that the world, as represented by our senses, depends for its existence on being perceived.

Shortly afterwards, Berkeley visited England, and was received into the circle of Addison, Pope and Steele. In the period between 1714 and 1720, he interspersed his academic endeavors with periods of extensive travel in Europe, including one of the most extensive Grand Tours of the length and breadth of Italy ever undertaken. In 1721, he took Holy Orders in the Church of Ireland, earning his doctorate in divinity, and once again chose to remain at Trinity College Dublin, lecturing this time in Divinity and in Hebrew. In 1724, he was made Dean of Derry.

In 1725, he began the project of founding a college in Bermuda for training ministers and missionaries in the colony, in pursuit of which he gave up his deanery with its income of £1100.

In 1728, he married Anne Forster, daughter of the Lord Chief Justice of Ireland. He then went to America on a salary of £100 per annum. He landed near Newport, Rhode Island, where he bought a plantation in Middletown, Rhode Island – the famous "Whitehall". It has been claimed that "he introduced Palladianism into America by borrowing a design from [William] Kent's Designs of Inigo Jones for the door - case of his house in Rhode Island [Whitehall]". He also brought to New England John Smibert, the British artist he "discovered" in Italy, who is generally regarded as the founding father of American portrait painting. Meanwhile, he drew up plans for the ideal city he planned to build on Bermuda. He lived at the plantation while he waited for funds for his college to arrive. The funds, however, were not forthcoming and, in 1732, he left America and returned to London.

While living in London's Saville Street, he took part in efforts to create a home for the city's abandoned children. The Foundling Hospital was founded by Royal Charter in 1739 and Berkeley is listed as one of its original governors. In 1734, he was appointed Bishop of Cloyne in Ireland, a position he was to hold until his death. Soon afterwards, he published Alciphron, or The Minute Philosopher, directed against both Shaftesbury and Bernard de Mandeville; and in 1735 – 37 The Querist.

His last two publications were Siris: Philosophical reflexions and inquiries concerning the virtues of tar - water, and divers other subjects connected together and arising from one another (1744) and Further Thoughts on Tar - water (1752). Pine tar is an effective antiseptic and disinfectant when applied to cuts on the skin, but Berkeley argued for the use of pine tar as a broad panacea for diseases. It is said that his 1744 book on the medical benefits of pine tar was the best selling book in his lifetime.

He remained at Cloyne until 1752, when he retired and went to Oxford to live with his son. He died soon afterward and was buried in Christ Church Cathedral, Oxford. His affectionate disposition and genial manners made him much loved and held in warm regard by many of his contemporaries.

The use of the concepts of “spirit” and “idea” is central in Berkeley’s philosophy. As used by him, these concepts are difficult to translate into modern terminology. His concept of “spirit” is close to the concept of “conscious subject” or of “mind”, and the concept of “idea” is close to the concept of “sensation” or “state of mind” or “conscious experience”.

Thus Berkeley denied the existence of matter as a metaphysical substance, but did not deny the existence of physical objects such as apples or mountains. ("I do not argue against the existence of any one thing that we can apprehend, either by sense or reflection. That the things I see with mine eyes and touch with my hands do exist, really exist, I make not the least question. The only thing whose existence we deny, is that which philosophers call matter or corporeal substance. And in doing of this, there is no damage done to the rest of mankind, who, I dare say, will never miss it.", Principles #35) This basic claim of Berkeley's thought is called "immaterialism" or, more commonly, subjective idealism. Incidentally, this claim is fundamentally different from the claim, sometimes inaccurately attributed to Berkeley, that to be is to be perceived (esse est percipi).

Hence, human knowledge is reduced to two elements: that of spirits and of ideas (Principles #86). In contrast to ideas, a spirit cannot be perceived. A person's spirit, which perceives ideas, is to be comprehended intuitively by inward feeling or reflection (Principles #89). For Berkeley, we have no direct 'idea' of spirits, albeit we have good reason to believe in the existence of other spirits, for their existence explains the purposeful regularities we find in experience. (“It is plain that we cannot know the existence of other spirits otherwise than by their operations, or the ideas by them excited in us”, Dialogues #145). This is the solution that Berkeley offers to the problem of other minds. Finally, the order and purposefulness of the whole of our experience of the world and especially of nature overwhelms us into believing in the existence of an extremely powerful and intelligent spirit that causes that order. According to Berkeley, reflection on the attributes of that external spirit leads us to identify it with God. Thus a material thing such as an apple consists of a collection of ideas (shape, color, taste, physical properties, etc.) which are caused in the spirits of humans by the spirit of God.

A convinced adherent of Christianity, Berkeley believed God to be present as an immediate cause of all our experiences.

He did not evade the question of the external source of the diversity of the sense data at the disposal of the human individual. He strove simply to show that the causes of sensations could not be things, because what we called things, and considered without grounds to be something different from our sensations, were built up wholly from sensations. There must consequently be some other external source of the inexhaustible diversity of sensations. The source of our sensations, Berkeley concluded, could only be God; He gave them to man, who had to see in them signs and symbols that carried God’s word.

Here is Berkeley's proof of the existence of God:

Whatever power I may have over my own thoughts, I find the ideas actually perceived by Sense have not a like dependence on my will. When in broad daylight I open my eyes, it is not in my power to choose whether I shall see or no, or to determine what particular objects shall present themselves to my view; and so likewise as to the hearing and other senses; the ideas imprinted on them are not creatures of my will. There is therefore some other Will or Spirit that produces them. (Berkeley. Principles #29)

As T.I. Oizerman explained:

Berkeley’s mystic idealism (as Kant aptly christened it) claimed that nothing separated man and God (except materialist misconceptions, of course), since nature or matter did not exist as a reality independent of consciousness. The revelation of God was directly accessible to man, according to this doctrine; it was the sense - perceived world, the world of man's sensations, which came to him from on high for him to decipher and so grasp the divine purpose.

Berkeley believed that God is not the distant engineer of Newtonian machinery that in the fullness of time led to the growth of a tree in the university quadrangle. Rather, the perception of the tree is an idea that God's mind has produced in the mind, and the tree continues to exist in the quadrangle when "nobody" is there, simply because God is an infinite mind that perceives all.

The philosophy of David Hume concerning causality and objectivity is an elaboration of another aspect of Berkeley's philosophy. A.A. Luce, the most eminent Berkeley scholar of the 20th century, constantly stressed the continuity of Berkeley's philosophy. The fact that Berkeley returned to his major works throughout his life, issuing revised editions with only minor changes, also counts against any theory that attributes to him a significant volte - face.

John Locke (Berkeley's predecessor) states that we define an object by its primary and secondary qualities. He takes heat as an example of a secondary quality. If you put one hand in a bucket of cold water, and the other hand in a bucket of warm water, then put both hands in a bucket of lukewarm water, one of your hands is going to tell you that the water is cold and the other that the water is hot. Locke says that since two different objects (both your hands) perceive the water to be hot and cold, then the heat is not a quality of the water.

While Locke used this argument to distinguish primary from secondary qualities, Berkeley extends it to cover primary qualities in the same way. For example, he says that size is not a quality of an object because the size of the object depends on the distance between the observer and the object, or the size of the observer. Since an object is a different size to different observers, then size is not a quality of the object. Berkeley rejects shape with a similar argument and then asks: if neither primary qualities nor secondary qualities are of the object, then how can we say that there is anything more than the qualities we observe?

In his Essay Towards a New Theory of Vision, Berkeley frequently criticized the views of the Optic Writers, a title that seems to include Molyneux, Wallis, Malebranche and Descartes. In sections 1-51, Berkeley argued against the classical scholars of optics by holding that: spatial depth, as the distance that separates the perceiver from the perceived object is itself invisible; namely, that space is perceived by experience instead of the senses per se.

Berkeley goes on to argue that visual cues, such as the perceived extension or 'confusion' of an object, can only be used to indirectly judge distance, because the viewer learns to associate visual cues with tactile sensations. Berkeley gives the following analogy regarding indirect distance perception: one perceives distance indirectly just as one perceives a person's embarrassment indirectly. When looking at an embarrassed person, we infer indirectly that the person is embarrassed by observing the red color on the person's face. We know through experience that a red face tends to signal embarrassment, as we've learned to associate the two.

The question concerning the visibility of space was central to the Renaissance perspective tradition and its reliance on classical optics in the development of pictorial representations of spatial depth. This matter was debated by scholars since the 11th century Arab polymath and mathematician Alhazen (al-Hasan Ibn al-Haytham) affirmed in experimental contexts the visibility of space. This issue, which was raised in Berkeley's theory of vision, was treated at length in the Phenomenology of Perception of Maurice Merleau - Ponty, in the context of confirming the visual perception of spatial depth (la profondeur), and by way of refuting Berkeley's thesis.

Berkeley wrote about the perception of size in addition to that of distance. He is frequently misquoted as believing in size - distance invariance — a view held by the Optic Writers. This idea is that we scale the image size according to distance in a geometrical manner. The error may have become commonplace, because the eminent historian and psychologist E.G. Boring perpetuated it. In fact Berkeley argued that the same cues that evoke distance also evoke size, and that we do not first see size and then calculate distance. It is worth quoting Berkeley’s words on this issue (Section 53):

“What inclines men to this mistake (beside the humour of making one see by geometry) is, that the same perceptions or ideas which suggest distance, do also suggest magnitude… I say they do not first suggest distance, and then leave it to the judgement to use that as a medium, whereby to collect the magnitude; but they have as close and immediate a connexion with the magnitude as with the distance; and suggest magnitude as independently of distance, as they do distance independently of magnitude.”

"Berkeley’s works display his keen interest in natural philosophy [...] from his earliest writings (Arithmetica, 1707) to his latest (Siris, 1744). Moreover, much of his philosophy is shaped fundamentally by his engagement with the science of his time." How profound this interest was can be judged from numerous entries in Berkeley’s Philosophical Commentaries (1707 – 1708), e.g. "Mem. to Examine & accurately discuss the scholium of the 8th Definition of Mr Newton’s Principia." (#316)

In addition to his contributions to philosophy, Bishop Berkeley was also very influential in the development of mathematics, although in a rather indirect sense. "Berkeley was concerned with mathematics and its philosophical interpretation from the earliest stages of his intellectual life." Berkeley’s “Philosophical Commentaries” (1707 – 1708) witness to his interest in mathematics:

Axiom. No reasoning about things whereof we have no idea. Therefore no reasoning about Infinitesimals. (#354) Take away the signs from Arithmetic & Algebra, & pray what remains? (#767) These are sciences purely Verbal, & entirely useless but for Practise in Societys of Men. No speculative knowledge, no comparison of Ideas in them. (#768)

In 1707, Berkeley published two treatises on mathematics. In 1734, he published The Analyst, subtitled A DISCOURSE Addressed to an Infidel Mathematician, a critique of the Calculus. Florian Cajori called this treatise “the most spectacular event of the century in the history of British mathematics.” However, a recent study suggests that Berkeley misunderstood Leibnizian calculus. The mathematician in question is believed to have been either Edmond Halley, or Isaac Newton himself — though if to the latter, then the discourse was posthumously addressed, as Newton died in 1727. The Analyst represented a direct attack on the foundations and principles of Infinitesimal calculus and, in particular, the notion of fluxion or infinitesimal change, which Newton and Leibniz used to develop the calculus. Berkeley coined the phrase Ghosts of departed quantities, familiar to students of calculus. Ian Stewart's book From Here to Infinity, (chapter 6), captures the gist of his criticism.

Berkeley regarded his criticism of calculus as part of his broader campaign against the religious implications of Newtonian mechanics – as a defense of traditional Christianity against deism, which tends to distance God from His worshipers.

The difficulties raised by Berkeley were still present in the work of Cauchy whose approach to infinitesimal calculus was a combination of infinitesimals and a notion of limit, and were eventually sidestepped by Weierstrass by means of his (ε, δ) approach, which eliminated infinitesimals altogether. More recently, Abraham Robinson restored infinitesimal methods in his 1966 book Non-standard analysis by showing that they can be used rigorously.

The tract Passive Obedience (1712) is "Berkeley’s main contribution to moral and political philosophy. [...] Other important sources for Berkeley’s views on morality are Alciphron (1732), especially dialogues I-III, and the Discourse to Magistrates (1738)." Passive Obedience is notable partly for containing one of the earliest statements of rule utilitarianism.

Berkeley's Treatise Concerning the Principles of Human Knowledge was published three years before the publication of Arthur Collier's Clavis Universalis, which made assertions similar to those of Berkeley's. However, there seemed to have been no influence or communication between the two writers.

German philosopher Arthur Schopenhauer once wrote of him: "Berkeley was, therefore, the first to treat the subjective starting - point really seriously and to demonstrate irrefutably its absolute necessity. He is the father of idealism...".

George Berkeley has gone down in the handbooks as a great spokesman of British empiricism.

Today, every student of the history of philosophy is familiar with the view that there was a sort of linear development involving three great “British Empiricists”, leading from Locke through Berkeley to Hume.

Berkeley influenced many modern philosophers, especially David Hume. Thomas Reid admitted that he put forward a drastic criticism of Berkeleianism after he had been an admirer of Berkeley’s philosophical system for a long time. Berkeley’s “thought made possible the work of Hume and thus Kant, notes Alfred North Whitehead.” Some authors draw a parallel between Berkeley and Edmund Husserl.

During Berkeley’s lifetime his philosophical ideas were comparatively uninfluential. But interest in his doctrine grew from the 1870s when Alexander Campbell Fraser, “the leading Berkeley scholar of the nineteenth century,” published “The Works of George Berkeley.” A powerful impulse to serious studies in Berkeley’s philosophy was given by A.A. Luce and Thomas Edmund Jessop, “two of the twentieth century’s foremost Berkeley scholars,” thanks to whom Berkeley scholarship was raised to the rank of a special area of historico - philosophical science.

The proportion of Berkeley scholarship, in literature on the history of philosophy, is increasing. This can be judged from the most comprehensive bibliographies on George Berkeley. During the period of 1709 - 1932, about 300 writings on Berkeley were published. That amounted to 1½ publication per annum. During the course of 1932 - 79, over one thousand works were brought out, i.e., 20 works per annum. Since then, the number of publications has reached 30 per annum. In 1977 publication began in Ireland of a special journal on Berkeley’s life and thought (Berkeley Studies).

The city of Berkeley, California, was named after him, although the pronunciation has evolved to suit American English. The naming was suggested in 1866 by Frederick Billings, a trustee of the then College of California. Billings was inspired by Berkeley's Verses on the Prospect of Planting Arts and Learning in America, particularly the final stanza: "Westward the course of empire takes its way; The first four Acts already past, A fifth shall close the Drama with the day; Time's noblest offspring is the last."

A residential college and an Episcopal seminary at Yale University also bear Berkeley's name, as does the Berkeley Library at Trinity College, Dublin.

Also named for him is Berkeley Preparatory School in Tampa, Florida. This leading private school is affiliated with the Episcopal Church, has almost 1300 students from pre-kindergarten through twelfth grade, and was founded in 1960.

Berkeley is honored together with Joseph Butler with a feast day on the liturgical calendar of the Episcopal Church (USA) on June 16.