Introductory Note: In 1995 Dr. Mortimer Adler wrote that idealism is “the greatest of all modern philosophical mistakes” (Adler 118). I believe that Dr. Adler is correct. Today, much of postmodernism, post-structuralism, and critical theory in all its forms is the result of idealism. To echo Richard Weaver, ideas have consequences. The next few posts will examine a particular form of idealism as represented by the Anglican bishop George Berkeley (1685 – 1753). The following posts will only look at Berkeley’s subjective idealism in general terms and then follow with the classical realist response. Berkeley’s most important and specific errors will be addressed later (such as his implicit Gnosticism). For now, just keep St. Athanasius in mind — That which is not assumed is not redeemed.

When it comes to understanding what is ultimately real (metaphysics), many of the truly great authors in the Western intellectual tradition can be divided between those who hold to idealism (that reality consists of mind and its ideas), and realism (that objects of sense perception exist independently of their being known). For the idealist, the mind is ultimate in determining reality, while the realist holds that being, or reality itself, is the proper starting point for philosophical reflection. The realist asserts that the realms of both consciousness (mind) and external objects exist and belong to the overall structure of Being. In one form or another, idealists believe that the contents of the mind are all that can be really known and the mind is the arbiter and, in some ways, creator of reality. In the history of Western thought, Berkeley, Kant, and Hegel hold to forms of idealism, and Aristotle, Aquinas, and Whitehead represent realism.¹ The next few posts will explore George Berkeley’s subjective idealism in light of classical realism (understood from the perspective of Aristotle and Aquinas), and assess the merits of holding to both mind and matter as the essential structure of reality, and explores whether or not Berkeley’s metaphysical position takes into account the first principles of being.

It is helpful to understand Berkeley’s version of subjective idealism before presenting and explicating classical realism. For Berkeley, perception is not simply direct sensation, it includes all the physical senses and mental ideas, including thinking, memory, imagination, and other faculties of the mind. In other words, perception extends to ideas, thoughts, consciousness, or mind. In fact, Berkeley specifically includes thinking with perception, “But my conceiving or imagining power does not extend beyond the possibility of real existence or perception. Hence, as it is impossible for me to see or feel anything without an actual sensation of that thing, so is it impossible for me to conceive in my thoughts any sensible thing or object distinct from the sensation or perception of it” (414). He further explains, “For the existence of an idea consists in being perceived” (413). For Berkeley, every thought, imagination, and memory, constitute perception and, further, all that one really has access to is idea or mental experience. The cognitive faculties of the mind—our images (including memory, imagination, or imaginary figures such as unicorns), concepts (conceptual truths such as mathematics and the laws of logic), and physical percepts all reside in the mind, and it is mental experience that is all one can know. All reality is ultimately reducible to mind or consciousness. Perception is mental experience and all reality equates to perception, “What do we perceive besides our own ideas or sensation” (413)? Accordingly, Berkeley insists that something must be perceived by the mind in order for it to be considered real, “It is indeed an opinion strangely prevailing amongst men, that houses, mountains, rivers, and in a word all sensible objects, have an existence, natural or real, distinct from their being perceived by the understanding” (414). For Berkeley, the individual perceiver is all-determining, since every thought, idea, and object is included in Berkeley’s definition of perception. This is Berkeley’s subjective idealism because all reality ultimately depends on the personal mental experiences of the perceiver.

Berkeley further explicates this notion with his famous phrase “esse is percepi”—to be is to be perceived, “For as to what is said of the absolute existence of unthinking things without any relation to their being perceived, that seems perfectly unintelligible. Their esse is percepi, nor is it possible they should have any existence out of the minds or thinking things which perceive them” (414). For Berkeley, the idea of an external reality that exists independently of the mind, or perception is conceptually incoherent. If a thing is not perceived, it does not exist. Essentially, Berkeley’s idealism follows this line of reasoning—all perceptions, concepts, and thoughts are ideas and can only exist in the mind. Therefore, everything exists only in minds. This does not mean, however, that something does not exist, or goes out of existence if it is not perceived or is no longer perceived. As an Anglican bishop, Berkeley believes God perceives everything and is the foundation of all reality. Because God perceives something, it is real and exists in reality (as part of God’s mind) even if no other individual is around to perceive it:

Such I take this important one to be, viz., that all the choir of heaven and furniture of the earth, in a word all those bodies which compose the mighty frame of the world, have not any subsistence without a mind, that their being is to be perceived or known; that consequently so long as they are not actually perceived by me, or do not exist in my mind or that of any other created spirit, they must either have no existence at all, or else subsist in the mind of some Eternal Spirit—it being perfectly unintelligible, and involving all the absurdity of abstraction, to attribute to any single part of them an existence independent of a spirit. (414)

In this manner, Berkeley suggests, as he does throughout his Principles of Knowledge, that he really does believe in an external reality because God or an Eternal Spirit perceives all things. For Berkeley, reality of a sort is possible and he narrowly escapes solipsism, which is often the end result of subjectivism. Nonetheless, all reality is fundamentally a mental perception or experience of the mind. For Berkeley, all reality is immaterial and ultimately exists in the mind of God.

As reality is not based on external matter, but on mind or a perceiving spirit, matter itself is illusory (429, 439-440). Only the most ignorant would believe that matter actually exists (423). In fact, Berkeley rejects the notion that a material world exists apart from mind, “But why should we trouble ourselves any farther, in discussing this material substratum or support of figure and motion, and other sensible qualities? Does it not suppose they have an existence without the mind? And is not this a direct repugnancy, and altogether inconceivable” (416)? Further, “The only thing whose existence we deny is that which philosophers call Matter or corporeal substance” (419).² Berkeley posits that immaterial mind is the foundation of all reality. For Berkeley, if there is a conflict between mind and matter, the subjective and objective, or appearance and reality, all one needs to do is simply eliminate external material existence and the problem is solved. What is left is mind-dependent subjective appearance.

In the next post, we will explore why Berkeley thought it was important for something to be perceived in order to exist which is the point of contention for classical realists.

1Both idealism and realism show up in Western thought in various forms. The categorization of these thinkers is for the purpose of a general grouping while acknowledging that particular differences and emphases can be found in each individual thinker. Neither school is monochrome in its outlook.

2Italics in the original. It is not clear to which specific philosophers Berkeley is referring. However, it is likely he has something like Aristotle’s definition of substance as a combination of matter and form in view.

Works cited

Adler, Mortimer. Adler’s Philosophical Dictionary: 125 Key Terms for the Philosopher’s Lexicon. Scribner, 1995.

Berkeley, George. The Principles of Human Knowledge. Great Books of the Western World. Vol. 55. Encyclopedia Britannica, Inc., 1999.