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Born 1685, Thomaston, near Kilkenny, Ireland

Died: 1753, Oxford, England

Major Works: An Essay towards a New Theory of Vision (1709), A Treatise concerning the Principles of Human Knowledge (1710), Three Dialogues between Hylas and Philonous (1713)

Major Ideas

To be is to be perceived. (A physical thing exists only when it is perceived through the use of the senses.)

Physical things are complexes of ideas (sensations).

Since no idea or sensation exists outside the mind, no physical thing exists outside the mind.

The primary qualities (solidity, extension, shape, motion) are as subjective as are the secondary qualities (color, sound, odor, taste, and texture).

The only kind of substance is spiritual substance: namely, that which perceives and thinks.

God accounts for the uniformity of nature and its continued existence when no finite mind perceives it; God causes the perceiving subject to have the ideas that constitute the external world.

George Berkeley is famous as history's most ingenious defender of philosophical idealism--the view that nothing exists other than God, finite spirits, and their ideas. The world that we think we encounter, a physical universe that existed long before there were any creatures to perceive it, is only an intellectual construction, according to Berkeley.

The argument for his theory proceeds step by step from the premise that there is a world we know, a world of trees, mountains, books, and letters on a page, to the conclusion that since all we know in the experience of these objects is our sensations of them, the objects themselves are nothing but collections of sensations or, as he called them, "sense qualities," such as blueness, hardness, smoothness, and so forth. Such qualities exist only in the mind; hence, "material objects--what we nowadays call "physical" objects--exist only in the mind. For any physical thing to be, to exist, then, it must be perceived.

Berkeley developed this intriguing theory, defended at length in both his Treatise Concerning the Principles of Human Knowledge and in the Dialogues between Hylas and Philonous, after having come to believe, as a result of his studies of vision, that the perception of the spatial features of things--their shape, magnitude, and movements--was derived from and entirely dependent upon fundamental experiences provided by seeing and touching. We do not immediately perceive such qualities (solidity, extension, shape, and motion) but only mediately or by reference to certain visual and tactual sensations. Analysis of the learning situation shows us, Berkeley concluded, that the "primary" qualities that Locke claimed are objective are just as subjective as are such "secondary" qualities as color and touch, on which we depend for our knowledge of spatial qualities.

Berkeley was educated at Kilkenny School and at Trinity College, Dublin. He became interested in philosophy and, in particular, in the problem of perception and its objects--a problem already presented to him through the work of Locke and Descartes. He became a fellow of Trinity College in 1707 and a short time later became an Anglican priest. His work on the theory of vision was published in 1709, when he was twenty-four. The other two attempts to win assent to his basic theory that material things must be perceived to exist and that they exist only in mind--namely, the Treatise Concerning the Principles of Human Knowledge and the Dialogues between Hylas and Philonous--were published within the next four years. Thus, his most important work in philosophy was completed by the time he was twenty-eight.

Berkeley was subsequently presented at court by his cousin, Lord Berkeley; he became a senior lecturer at Trinity College and, later, dean of Derry.

Berkeley then conceived the idea of founding a college in Bermuda and after receiving a charter from George I, he married Anne Forster and in 1728 sailed to Rhode Island, where he took up residence in Newport. However, when in 1731 the funds promised by England for the college in Bermuda were not forthcoming, he and his wife returned to England.

He was made bishop of Cloyne in 1734 and for the next twenty years devoted himself to improving the social conditions in his diocese. His last published book was Sins: A Chain of Philosophical Reflexions and Inquiries Concerning the Virtues of Tar-Water, and Divers Other Subjects (1744). Tar-water, derived from the pitch of pine trees, was touted by Berkeley as practically a cure-all, and the "divers other subjects" he mentions in his title included such matters as studies of the Trinity, free will, space and time, and God's essential nature.

Despite his eccentricities, Berkeley was a careful thinker and a brilliant writer. The Principles is a subtly developed argument for his central theory, and the Dialogues is a lively and imaginative presentation of the opposing views of materialism (represented by Hylas) and Berkeley's metaphysical idealism or immaterialism (represented by Philonous).

Although few readers have been persuaded by Berkeley and few philosophers, in his time or later, have been enthusiastic followers, his reputation remains strong because of the degree to which he made credible the claim that empirical knowledge is grounded in sense experience and that there is no knowledgeable way of going beyond such experience. Of course, Berkeley himself attempted to go beyond such experience by arguing for God as the cause of our sense-ideas, but he was no more successful in that enterprise than his materialist opponents were in establishing their own metaphysical position. Ironically, despite Berkeley's philosophical and literary genius, the victors turned out to be the skeptics--culminating in Hume--against whom Berkeley had built his case: in making sense experience fundamental, Berkeley created an empirical philosophy that skepticism was able to exploit.

Treatise Concerning the Principles of Human Knowledge

Berkeley's Treatise Concerning the Principles of Human Knowledge is both an argument against the proposition that there are "abstract ideas" and an argument for the proposition that "esse is percipi" (to be is to be perceived). These two ideas are, of course, related: If all knowledge depends on sensations, then no knowledge can be derived from ideas that are presumed to be wholly abstract and without sense content.

In the introduction to the Principles, Berkeley argues that a principal cause of difficulties and errors in philosophy has been the notion that there are abstract ideas. It has been supposed that it is possible to draw from the experience of a number of particular things some common feature that is the focus of an abstract idea. Berkeley points out that he does not deny that there are "general" ideas, only that there are "abstract general ideas." He maintains that a word becomes general by being made the sign of several particular ideas, not of an abstract idea.

The cause of the mistaken view that there are abstract general ideas is, Berkeley claims, language. Were it not for language with its terms of general signification, there would be no likelihood of anyone's holding the opinion that there are abstract ideas. But reflection on language is sufficient to show to anyone who faces the facts honestly that a general term acts as a sign of a number of particular matters, not of an abstract feature common to them all.

Berkeley begins the main text of the Principles with the claim that the "objects of human knowledge" are either "ideas actually imprinted on the senses, or else such as are perceived by attending to the passions and operations of the mind, or lastly, ideas formed by help of memory and imagination." From the outset, then, he emphasized his central point--that the mind knows only "ideas" and thus cannot know a world of material objects beyond ideas.

He uses the term "ideas" to include what we would call sensations, as in the sentence "By sight I have the ideas of light and colors ...," and again, "Smelling furnishes me. with odors, the palate with tastes, and hearing conveys sounds to the mind ..." Finally, be claims forthrightly that groups of such ideas furnished by the senses "come to be marked by one name, and so to be reputed as one thing And he offers a clear example: "A certain color taste smell figure, and consistence having been observed to go together, are accounted one distinct thing signified by the name 'apple.'..." Other examples of collections of sense-ideas that constitute what he calls "sensible things" are a stone, a tree, and a book.

Berkeley then claims that, in addition to sensible things, there is that which perceives them, that which wills, imagines and remembers: "what I call 'mind,' 'spirit soul or 'myself.'"

Then, having pointed out that no one supposes that thoughts, passions or products of the imagination exist "without (outside) the mind, he argues that the same is true of sensations and the objects constituted by them Sensible things exist only in the mind and cannot exist elsewhere. "Their esse is percipi," he writes nor is it possible they should have existence out of the minds or thinking things which perceive them."

Berkeley concedes that people commonly believe that such objects as houses, mountains, and rivers have an existence distinct from their being perceived but he insists, such a belief involves a contradiction Objects such as houses and mountains are things we perceive by sense" and since the only objects of sense perception are sensations ("our own ideas ) and since sensations could certainly not exist unperceived, then it would be contradictory to say for example, that a house, which is a set of sensations and thus could not exist unperceived, may exist unperceived.

The author goes on to argue that since the being of a sensible thing consists in its being perceived, and since only spirits (minds) perceive, "there is not any other substance than spirit, or that which perceives."

Nor,, Berkeley continues, can the ideas be copies or resemblances of objects presumed to exist independently of perception for "an idea can be like nothing but an idea."

He rejects Locke's distinction between primary qualities (extension, figure, motion, solidity, etc.) and secondary qualities (sensible qualities-colors, tastes, and so forth). Since the only ideas we have of such features as extension and solidity are ideas built from sense-ideas, Berkeley argues, these derived features, like the other sense qualities, must be perceived in order to be: Neither the primary nor the so-called secondary qualities can exist outside the mind.

Although Berkeley argues that the idea of material substance (objects existing independently of perception) is contradictory, he takes some time to point out that even if there were any such substance existing without relation to any mind or spirit, then precisely because of that independence, we would never be able to know such a substance. Its existence, then, would make no difference. This, together with the fact that it makes no sense to suppose any such substance, makes the case against the materialist complete. (Berkeley's argument here has a pragmatic cast that foreshadows the philosophical method of William James.)

Berkeley then develops his idea of spirit; more precisely, he argues that no idea of spirit is possible, in that spirit is not like sense-objects, not a set of ideas, but "that which acts" -that which perceives, wills, remembers, and so forth. Spirit cannot itself be perceived, Berkeley argues; it can be known only by "the effects it produces."

Having concluded that we cannot know even ourselves and certainly not other spirits except "by their operations, or the ideas by them excited in us," Berkeley goes on to argue that the works of nature (themselves ideas) would be unaccountable were it not for the presumption that there is some spirit other than a human spirit that causes them. The wonders of nature make evident the wonders of the spirit that realizes them; the order and regularity of nature, together with its harmony and beauty, are evidence of a spirit recognized as being "one, eternal, infinitely wise, good, and perfect Berkeley thus contends that "God is known as certainly and immediately as any other mind or spirit whatsoever distinct from ourselves."

By attributing the continuity of nature and its very existence to God, who enables finite spirits to have the ideas that for them constitute the things of this world, Berkeley builds his case for immaterialism as opposed to materialism.

It is this feature of Berkeley's thought that has been fixed in the popular mind by the famous Ronald Knox limerick:

There was a young man who said, "God

Must think it exceedingly odd

If he finds that this tree

Continues to be

When there's no one about in the Quad."

And the reply:

Dear Sir: Your astonishment's odd:

I am always about in the Quad.

And that's why the tree

Will continue to be,

Since observed by yours faithfully,


Three Dialogues between Hylas and Philonous

When Berkeley found that his Principles was not persuading the thinkers of his time--in fact, it was largely ignored and was more laughed at than read--he wrote the Dialogues, hoping that the give-and-take of disputational discussion would be more effective than a straightforward essay in making both his negative argument (against abstract ideas and materialism) and his positive argument (that only ideas and the spirits that have them exist and that ideas must be perceived in order to be) clear and persuasive.

The basic argument in the Dialogues is the same, but it is developed in a very entertaining way in the course of an imaginary dialogue between Hylas (literally, the materialist) and Philonous (literally, the lover of reason, the immaterialist). The latter is, of course, Berkeley's spokesman.

Out of a series of questions and responses comes an argument by Philonous that we here represent as a chain argument:

1. Sensible things (objects of sense) are such things as apples, wooden things, fires, stones, iron, letters on a page, and so forth.

2. We know things of these kinds, sensible things.

3. Whatever is knowable by us is perceivable by the senses.

4. Anything perceivable by the senses is immediately (that is, not by the use of reason) perceivable.

5. Anything immediately perceivable (such as colors, sounds, pains, odors) is a sense quality.

6. Sense qualities (such as blueness, hotness, bitterness) are sensations.

7. Sensations are ideas ("imprinted on the senses").

8. Ideas are only within the mind.

9. Whatever is within the mind is perceived.


Conclusion: Sensible things are perceived.

Note that it follows from this argument that apples, fires, trees, stones, mountains--those objects we apprehend through the use of the senses--are perceived, that is, are not simply perceivable but are actually gasped by a perceiver in sense experience. That is the radical conclusion common to both the Principles and the Dialogues.

Hylas, supposing himself to be talking about material (physical) objects that he presumes exist independently of sense experience, finds it possible to assent to propositions 1 through 5. We do know apples, trees, and so forth, through becoming aware of their sense qualities (or properties, characteristics) such as redness, sweetness, smoothness, and so forth.

But clever Philonous asks Hylas whether the heat of a fire, which is surely a sense quality, is sometimes a "very great pain," as when one puts one's hand in the fire.

And Hylas agrees that the heat of a fire may be a very great pain.

But, Philonous points out, pressing on with the argument, a pain is a sensation only within the mind: For a pain to be, it must be perceived (felt).

Accordingly, the heat, when it is a very great pain, is also only within the mind; the heat, like any pain, can be (exist) only when it is known as a sensation.

What is true of some sensations is true of them all, he then forces Hylas to admit: For them to be, they must be perceived.

And so the conclusion is forced upon Hylas: The material, physical things of this world, the things we know in the course of experience, are sensations and, hence, such that for them to be, they must be perceived.

(There are two ways of describing Hylas's mistake, if, indeed, one treats Hylas--Berkeley's invention--as if he were an actual person: Either Hylas failed to realize that throughout the argument Philonous was talking about what might be called "the World of our experience," the "interior world," the world we know as we know the world of our dreams, or Hylas failed to realize that Philonous, after having used the term "sense quality" in such a way that Hylas took him to mean a causal property, the capacity of an external physical object to cause a sensation, used the very same term in such a way that Hylas took him to mean a sensation. Hylas was thus confused and taken in by a switch in the use of the key term "sense quality"--and of corresponding terms, such as "heat.")

Although the Dialogues is lengthy, the three dialogues making up an extended work amounting to a book, its central message is that incorporated in the summary above. (It is worth reading as a whole, however, both for the refinements of argument and to make possible a full appreciation of the author's philosophical ingenuity and perceptiveness.)

Further Reading

Dancy, Jonathan Berkeley: An Introduction. Oxford and New York: Blackwell, 1987. An introduction (both demanding and rewarding) to the Principles and the Dialogues, designed for students and other interested "amateurs." Dancy is careful to point out where his interpretations differ from those of other critics.

Foster, John, and Howard Robinson. Essays on Berkeley: A Tercentennial Celebration. Oxford: Clarendon Press 1985. Twelve philosophical critics from British and American universities, including J. O. Urmson of Oxford, offer fresh discussions of Berkeley s central ideas.

Gaustad, Edwin S. George Berkeley in America. New Haven and London: Yale University Press, 1979. Gaustad professor of history at the University of California Riverside, here presents a thorough and philosophically literate account of Berkeley's stay in the United States.

McGreal, Ian P. Analyzing Philosophical Arguments. San Francisco: Chandler, 1967. Includes an analysis of Berkeley's argument, drawn from the Principles and the Dialogues, involving a summary and a premise-by-premise critique. The emphasis is on Berkeley's persuasive uses of key terms.

Pitcher, George. Berkeley. London, Henley, and Boston: Routledge & Kegan Paul, 1977. One in a series of books in The Arguments of the Philosophers series edited by Ted Honderich of University College, London, Pitcher's careful and extensive account of Berkeley's ideas is both analytic and critical.

Urmson, J. 0. Berkeley. Oxford and New York: Oxford University Press, 1982. A distinguished Oxford scholar's refreshingly brief but perceptive account of Berkeley's philosophy. Urmson finds fault with Berkeley's basic premises but regards him as "one of the most gifted and readable of philosophers..."
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Publication:Great Thinkers of the Western World
Article Type:Biography
Date:Jan 1, 1999
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