Sophia on the web

A Resource Guide for Philosophy Students

Created by Jennifer Leslie Torgerson, MA

This page last modified: October 14, 2012

copyright, 1997 - present


School of Athens


George Berkeley

1685 1753 CE





Baird and Kaufmann. Philosophical Classics: From Plato to Nietzsche, 2nd Edition. (Upper Saddle River, NJ: Prentice Hall, 1997 [1994]).


Frederick Copleston, A History of Philosophy: Book Two. (New York, NY: Doubleday, 1985 [1944]).


__________, A History of Western Philosophy: Hobbes to Hume, 2nd Edition. (San Diego, CA: Harcourt Brace, 1980 [1952]).


Daniel Kolak. The Mayfield Anthology of Western Philosophy. (Mountain View, CA: Mayfield Publishing, 1998).


Louis P. Pojman. Classics of Philosophy. (New York, NY: Oxford University Press, 1998).


T. V. Smith and Marjorie Grene. Philosophers Speak for Themselves: Berkeley, Hume, and Kant. (Chicago, IL: University of Chicago Press, 1957 [1940]).



The principle works of Berkeley


A Defense of Free Thinking in Mathematics (1735)

A Word to the Wise (1749)

Alciphon or the Minute Philosopher (1732)

An Essay towards preventing the Ruin of Great Britain (1721)

De motu (1721)

Essay Towards a New Theory of Vision (1709)

Farther Thoughts on Tar-water (1752)

Passive Obedience (1712)

Siris (1744)

The Analyst or a Discourse addressed to an Infidel Mathematician (1734)

The Notebooks (of 1707 and 1708)

The Querist (1735-37)

The Theory of Vision or Visual Language showing immediate Presence and Providence of a Deity Vindicated and Explained (1733)

Three Dialogues Between Hylas and Philonous (1713)

Treatise Concerning the Principles of Human Knowledge (1710, part 1)

George Berkeley and Subjective Idealism

What is idealism? Idealism (or more correctly "idea-ism") is sometimes called mentalism or immaterialism. Idealism (of the subjective kind) is the theory that the universe is an embodiment of the mind. Idealism is best defined as the view that all reality is immaterial, or idea.  Metaphysical idealism assumes an epistemological idealism. [i.e. solipsism: (solus = alone, ipse = self) the theory that nothing can be known but mind and its mental content, which can be seen as a solipsism.  Solipsism is the reductio ad absurdum of subjectivity.] According to idealists, matter, or the physical does not exist.

There are two types of idealism that will discussed in class: subjective idealism and objective idealism.

subjective idealism: The view that reality is our experience of things. "To be is to be perceived" (Esse est percipi) according to Bishop George Berkeley (1685- 1753), an Irish philosopher of Irish descent. Berkeley wrote several works, but the most important is Three Dialogues between Hylas and Philonous (1713), which was his third work, completed when he was 28. Berkeley meant by esse est percipi that nothing but minds and ideas exist. To say that an idea exists means, according to him, that it is being perceived by some mind. For ideas, Esse est percipi: to be is to be perceived. Minds themselves, however, are not similarly dependent for their existence on being perceived. Minds are perceivers. To give Berkeley's full meaning we must say: To be is to be perceived (ideas) or to be a perceiver. All that is real is a conscious mind or some perception or idea held by such a mind. How, Berkeley asks, could we speak of anything that was other than an idea or mind? The mind exists as it is thought in the mind of God. Berkeley was also known for holding the position that there is no material substance, hence Berkeley is also, and prefers to be, called an immaterialist.

This is a subjective idealism. The subjectivist holds that there can be no object, as well as no perception of it, without a knower; that the subject (mind or knower) in some way creates its object (what we call matter, or things that are known); and that all that is real is a conscious mind or a perception by such a mind. To say that a thing exists is to say that it is perceived. What would anything or could anything be apart from its being known, no one could think or say. What we think and see is mind-dependent, and the world is mental dependent.  Even so, Berkeley was an empiricist, since all knowledge is acquired after being perceived by the senses.

Berkeley accepted the psychology of John Locke (1632- 1704), who said that our knowledge deals only with ideas.  (Don't forget that Locke, like Berkeley, was an empiricist).  Locke accepted the existence of spiritual substance, ideas, and material substance. Locke distinguished between the primary qualities of matter (form, extension, solidity, motion, number, and so on) and secondary qualities (colors, sounds, tastes, odors, and the like). The secondary qualities, according to Locke, are not in the material substance; they are in the mind or they are the way in which the primary qualities affect the mind or knower, and they vary from person to person. Berkeley went further than Locke and attempted to show that the primary qualities, as well as the secondary qualities, do not exist apart from minds. Berkeley, therefore, called both primary and secondary qualities "ideas" and concluded that what we refer to as a material object is simply a collection of ideas. Berkeley insisted that the arguments used by Locke to prove the subjectivity of the secondary qualities also demonstrate the subjectivity of the primary qualities.

5 proofs for subjective idealism (in summary)

1.  The discontinuity of dualism;

2.  Matter as a meaningless idea;

3. The unexperienced as unconceivable;

4.  The inseparability of primary and secondary qualities of objects;

5.  The relativity of all qualities.

Berkeley uses a reductio ad absurdum argument against extended substance (matter), by saying that extension is relative to the perceiver, and that an object would have more than one extension at the same time.  This also shows that extension is a secondary, not a primary quality of an object.  And what of substance, or that which underlies a thing?  Does it too have extension? Is it not absurd to claim that that which underlies extended things is itself not extended?  And since substance has no accidents, or qualities, but stands under them, can we know anything of substance?  Substance, if it is that which underlies, is not perceivable.  Objects could not cause effects in a mind without a mind existing.  Only ideas can be perceived.  Material things are in themselves, insensible, and exist only as perceptions.  Esse est percipi.

According to Berkeley, creation is a continual process.  There was not a singular act of creation.  God constantly maintains and sustains all that is perceived; God is the ultimate perceiver.

Objective idealism: To avoid the difficulties inherent within subjective idealistic positions, others have developed objective idealistic theories. Objective idealism is the view that the world out there is Mind (or God) communicating with our (human) minds. An example of this metaphysical objective idealistic theory is that if the Ideal Forms developed by Plato. (c. 428- c. 348 BCE). Plato did not call himself an idealist since the term was not then in use. (Especially see the dialogues: The Republic and Phaedo). Plato held that the material or phenomenal world (the world of appearances or BECOMING) is in a state of flux attempting to emulate (unsuccessfully) the Ideal Forms (the noumenal world or BEING). The Forms exist independently of the consciousness. The noumenal world of BEING is the true permanent world of reason.

Some criticisms of Subjective + Objective Idealism:

OBJECTIVE + SUBJECTIVE (1) Realists are likely to charge that idealism goes beyond all empirical evidence and that its "proofs" resort to metaphor and flights of the imagination based on the hopes and wishes of men.

SUBJECTIVE (2) When idealists claim that existence is dependent on some mind, the realists is likely to insist that "being perceived" is an accidental feature of an object, where as existence is an essential feature.

SUBJECTIVE (3) The subjectivist is accused of a misuse of the word idea when they use it both for the "concept held by the knower" and the "object known". This double use of the word 'begs the question' and assumes without proof that there is no real difference between the mind and that toward the mind's experience is directed.

The strength of idealism is that it justifies, philosophically, the notion that the individual self has meaning and dignity.