Three Dialogues Between Hylas and Philonous

by George Berkeley
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In Three Dialogues Between Hylas and Philonous, George Berkeley defends the view that matter does not exist, that the universe contains minds or spirits but no realm of atoms and molecules. Berkeley argues that things that are normally considered material objects—stones, trees, shoes, apples—have no existence outside the minds and experiences of conscious beings. Like an object in a dream, a stone has no existence outside consciousness. If all conscious beings were to stop perceiving some sensible object—the moon, for example—that object would cease to exist. Although Berkeley’s book owes its philosophical greatness to the many important arguments that are presented in support of the main thesis, the work is also notable for the simplicity and clarity with which the ideas are conveyed. The ideas are presented in the form of a dialogue between Hylas, a materialist, and Philonous, the representative of Berkeley’s idealism.

Perception as the Basis of Reality

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The main argument in the work centers on an examination of the set of properties of which sensible objects are composed. Berkeley first examines the properties that philosophers have called “secondary qualities” (heat, taste, sound, smell, color) and argues that these properties have no existence outside sensations and perceptions in the minds of perceivers. He then argues that the same sorts of considerations will show that what have been called the “primary qualities” of sensible objects—extension (length and width), shape, hardness, weight, motion and other characteristics—also have no existence outside the perceptions of conscious beings. In arguing that every property that a sensible object has exists only as a sensation or a property of a sensation within a mind, Berkeley is showing that the entire sensible object has no existence outside the mind. For Berkeley, a cherry is nothing over and above the sensations experienced in connection with it. “Take away the sensations of softness, redness, tartness, and you take away the cherry,” he writes.

Secondary Qualities Exist Only in the Mind

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Berkeley begins his argument by reference to heat. Intense heat, like intense cold, is pain; it is intrinsically unpleasant. Pain, like pleasure, is a kind of experience; it is something that cannot exist outside someone’s consciousness. Therefore, when someone feels intense heat or intense cold, Berkeley reasons, what he feels is in his own mind, not in some inert, unfeeling object existing outside his consciousness. To be aware of intense heat is simply to be aware of a particular kind of pain sensation.

To the objection that intense heat is a cause of pain and not itself literally “pain,” Berkeley replies that when one is perceiving intense heat, the heat of which one is aware is not distinguishable from the pain sensation of which one is aware. In perceiving the heat, the person is not aware of two things, heat and a pain sensation, but of only one thing, a painful sensation.

The temperature that an object appears to have differs under different circumstances, Berkeley proceeds. If one’s left hand is hot and one’s right hand cold and both hands are immersed in a bowl of water, the water seems cool to the left hand and warm to the right hand. From this fact, Berkeley concludes that the heat that one feels cannot be a feature of some object existing outside one’s mind. No single object could have the incompatible properties of warmth and coolness at once. Berkeley concludes that the warmth and coolness that one perceives are sensations within one’s own experience. What one thinks of as the “temperature” of the water is simply the sensation experienced in connection with the water. The sensation is in the consciousness of the person perceiving the temperature, not in an unfeeling object outside one’s consciousness.

These arguments concerning heat can be paralleled for the other secondary qualities of sensible objects. A sweet taste is a form of pleasure; a bitter taste is intrinsically unpleasant or painful. Because pleasure and pain are necessarily mental phenomena, a sweet or bitter taste, because it is a pleasure or pain, must itself be a mental phenomenon, Berkeley reasons. Furthermore, the taste that people perceive in an object varies under different conditions. A food that one finds sweet at one time may seem bitter or tasteless another time. The taste a food has when one is sick differs from its taste when one is well, Berkeley writes. What differs in the two cases, he reasons, is not the alleged external object but the experience had when tasting the food. In each case, one has different taste sensations, and these taste sensations, which are the taste of the food, exist in the mind of the person doing the tasting. Berkeley considers the fact that some people delight in the very food that others find repulsive to be further proof that the taste of a food is not a property inherent in the object that allegedly exists outside people’s minds but a sensation undergone by the people who taste the food. Similar arguments support the claim that odor or smell is a sensation within someone’s mind.

As happens with other secondary qualities, the color that an object appears to have varies under different conditions. A cloud that appears to be some shade of white under most conditions may appear red or purple when perceived at sunset, Berkeley writes. Someone who holds that color is an inherent property of the clouds will need to say that not all the colors that may be perceived in an object are the true color of the object and that some of these colors are only apparent.

How then is the true color to be distinguished from the colors that are said to be merely apparent? It might be suggested that the true color is the one the object presents when it is viewed under white light. However, this suggestion raises problems. An object presents a somewhat different color under candlelight from that which it presents under daylight, Berkeley notes. Indeed, there are many different intensities and shades of what we call “white light,” and each of these intensities and shades is as normal and common as the others. Yet each shade and intensity leads to a somewhat different color being perceived in an object.

One might reply that the true color of an object is the color that is perceived when the object is given the most close and careful inspection possible. However, this suggestion also runs into serious problems. To examine an object in the closest and most careful manner possible is to examine the object under a microscope, Berkeley writes. However, when an object is examined under a microscope, the microscope does not simply present one color to the eye, a color which one could label the true color; rather, the microscope (like the naked eye) presents numerous colors to the eye, and the particular color one sees in an object depends on the magnification one gives to the microscope. To pick out one color from the various colors which are perceived and call it the true color of the object would require a choice which has no justification.

A further problem for someone who maintains that color is a property inherent in objects exterior to minds is the fact that objects under the same conditions present different colors to different perceivers. Objects that appear yellow to people with jaundice appear other colors to people without jaundice, Berkeley writes. Furthermore, given the structural differences between the eyes of animals and those of people, it is probable that some animals perceive colors in objects that are different from those that people perceive, Berkeley reasons. To pick out any of these perceived colors and call it the true color would involve an arbitrary, unjustifiable decision. The view that an object has a true color Berkeley considers untenable in face of the above facts. From these considerations, Berkeley concludes that all colors perceived in sensible objects are simply visual sensations in the minds of those perceiving the color.

The accounts that scientists give of perception are often consistent with Berkeley’s account of secondary qualities and may even be interpreted as supporting it, Berkeley writes. Although scientists do, of course, believe in a material world existing external to consciousness that causes people to hear sounds and see colors, they often think of hearing or seeing as a matter of having certain auditory or visual sensations. Scientists say, for example, that when an object causes air to move in a certain manner and this air strikes the eardrum, a certain neurological activity is produced, and the neurological activity causes one to experience the sensation of sound. Color is seen, they say, when light rays, after being reflected off some object, enter the eye and stir the optic nerve such that a message is communicated to the brain, upon which the person experiences the sensation of color. To say, as these scientists do, that sound and color are sensations is to say that they are mental phenomena. The view that “secondary qualities” are nothing but sensations in the minds of conscious beings, although strange in relation to common sense, did not originate with Berkeley. The view had been previously defended by John Locke. Berkeley’s most radical departure from previous philosophical opinion was in his claim that all properties of sensible objects, including the primary qualities, could be shown to have no existence outside the minds of perceivers.

Primary Qualities Exist Only in the Mind

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If the existence of perceptual variation is reason to conclude that the secondary qualities do not exist outside minds, Berkeley reasoned, then philosophers have the same reason to conclude that the primary qualities also lack existence outside minds. Like the secondary qualities, the primary qualities give rise to radical perceptual variations. The extension that an object appears to have varies as the object is perceived from different positions, Berkeley explains. The visible extension that a tree has, the extension that it has in relation to the expanse of a perceiver’s field of vision, grows larger as the perceiver approaches the tree and shrinks as the perceiver moves away from the tree. When a perceiver is near, a tree may appear to be a hundred times larger than it does from a great distance. (Imagine how much larger the moon would look if one could see it from a distance of only ten miles.) It does not help to reply that the tree has the same size in feet and inches whatever one’s distance from it, for the visible extension of a foot or an inch itself is not a constant, and it too goes through the same variations as one approaches or recedes from it. A twelve-inch ruler looks large from very close but tiny when perceived from a distance. Furthermore, Berkeley argues, a sensible object may present differing visible extensions at one and the same time. The foot of a mouse, which seems tiny to a person, would seem to be of considerable extension to the mouse. An object that extends over a large portion of the field of vision of a mouse would extend over a small portion of the visual field of a person. Berkeley concludes that the extension of a sensible object is not a property of an object that exists outside consciousness but a property of a sensation in the mind of a perceiver.

The types of considerations which show that the extension of a sensible object has no existence outside a mind also show that shape, hardness, and the other primary qualities are only properties of sensations within the minds of perceivers. The shape, hardness, and motion which an object appears to have also vary from one perceiver to another and vary for a single perceiver when the object is viewed under different conditions.

One might think that the fact that objects are perceived as being at a distance from the person perceiving them proves that the objects cannot be inside the perceiver’s mind. Berkeley responds to this objection with the observation that even in dreams and hallucinations objects are experienced as being at a distance and outside the mind, yet in spite of these appearances these imagined objects do not exist outside the mind of the person imagining them. Thus it clearly is possible for an object to be experienced as being at a distance from oneself even when the object is really not outside one’s own mind.

Another reason the primary qualities must be in the mind with the secondary qualities, Berkeley writes, is that all sensible qualities coexist. When one perceives a table, the extension and shape that one perceives are joined to the color. The shape outlines the color. If the color that is perceived is in one’s mind, then so are the extension, shape, and motion that are experienced as being together with the color.

It might be supposed that when one perceives an object one has an image in one’s mind that copies or mirrors a material world existing outside one’s mind—a world that is the cause of the image. Although it is the mental image and not the material world of which a perceiver is directly aware, the image provides accurate information about the external, material world, it may be said. Berkeley finds serious problems in this view. First, if it is admitted that all the primary and secondary qualities of objects exist only within minds, then there are no properties remaining for this so-called “material substance” outside the mind to have. Talk of material substance in this context becomes meaningless. Furthermore, it is not possible, Berkeley argues, for an image that is continually undergoing radical changes (which one’s perception of sensible objects is doing) to be a copy of some set of objects that remains unchanged throughout this period (as the alleged material substance is assumed to do).

A further problem with this view, Berkeley argues, is that the model of perception that it presents leads to a severe skepticism about the alleged material world. According to this view, one who perceives a sensible object is not directly aware of the material world but only of the image in one’s mind. That this image, which is said to be a copy of a material world outside the mind, does indeed copy or resemble the object alleged to be the original could not be known. If one’s knowledge of the alleged original is derived entirely from one’s familiarity with the image that is said to be the copy, there is no independent means of checking that the “copy” is actually like the original. Indeed, because in this view people are never directly aware of the alleged material world, it follows that it is not possible even to know whether this outside, unexperienced world exists. The existence of a mental image does not itself guarantee that there is an external object causing the image, for it is logically possible for someone to have exactly the same perceptions or mental images even if no world of material objects exists.

Reality as Spirit

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If what one considers real objects are like objects in dreams and hallucinations in having no existence outside the mind, how then does Berkeley distinguish the former from the latter? Berkeley explains that the perceptions one considers real are vivid and consistent in a way that those that one does not consider real are not.

What then is the cause of people’s perceptions of sensible objects if not a world of material substance corresponding to those perceptions? Berkeley reasons that because one does not cause or coordinate one’s own sensations, one’s sensations must have a cause outside oneself, and this cause, Berkeley concludes, is an omnipresent infinite Spirit. >From the order, beauty, and design with which one’s sensations appear Berkeley concludes that the designer is wise, powerful, and good “beyond comprehension.”


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Additional Reading

Berman, David. Berkeley. New York: Routledge, 1999. An excellent biographical introduction to the thoughts of the philosopher, clearly presented and requiring no special background. Bibliography.

Berman, David. George Berkeley: Idealism and the Man. New York: Oxford University Press, 1994. This worthwhile analysis of George Berkeley’s distinctive philosophical positions focuses on his religious thought. Contains considerable information about Berkeley’s life and his considerable influence.

Bonk, Sigmund. “We See God”: George Berkeley’s Philosophical Theology. New York: Peter Lang, 1997. A good analysis focusing on Berkeley’s spiritual thoughts.

Dancy, Jonathan. Berkeley: An Introduction. New York: Basil Blackwell, 1987. Dancy provides a helpful introduction that is useful for beginning students.

Foster, John, and Howard Robinson, eds. Essays on Berkeley: A Tercentennial Celebration. New York: Oxford University Press, 1985. This collection contains important interpretations of Berkeley’s philosophy by leading scholars in the field.

Jones, W. T. A History of Western Philosophy: Hobbes to Hume. New York: Harcourt, Brace and World, 1969. Offers a clear and accessible introduction to the key theories in Berkeley’s philosophy.

Muehlman, R. G., ed. Berkeley’s Metaphysics: Structural, Interpretive, and Critical Essays. University Park: Pennsylvania University Press, 1995. A good collection of essays that analyze and criticize Berkeley’s metaphysical idealism.

Richie, A. D. George Berkeley: A Reappraisal. Manchester, England: Manchester University Press, 1967. Richie argues that the key to understanding Berkeley is found in his theory of vision.

Turbayne, Colin M. Critical and Interpretive Essays. Minneapolis: University of Minnesota Press, 1982. Turbayne’s essays explore key aspects of Berkeley’s theory of knowledge and metaphysics.

Urmson, J. O. Berkeley. Oxford: Oxford University Press, 1982. A reliable commentary on Berkeley’s thought by an influential twentieth century philosopher.

Warnock, G. J. Berkeley. London: Penguin Books, 1953. This introduction is particularly useful in its account of Berkeley’s views of science, mathematics, and language.