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Gordon Kennedy

Berkeley's Idealism

In this essay I shall give the historical background to Berkeley's Idealism and then offer an argument for Idealism and suggest how an idealist could defend his theory against common objections and criticisms.

Bishop George Berkeley's Idealism or Immaterialism is the theory that the physical world exists only in the experiences minds have of it. Berkeley's Idealism restricts minds to God, human beings, animals and whatever other spirits there may commonly thought to be, and says that everything else — the intrinsically non-mental — exists only as features of the experience of these minds.

Although this would initially seem to be a bizarre view, if we look at the science and philosophy of the seventeenth century, it arises quite naturally.

The philosophy of the era derived from the 'new' science of the period. Isaac Newton was the prominent scientist of the age, and John Locke was the most notable philosopher in converting Newtonian science into a philosophy. However, the age produced many other scientists and philosophers who were responsible for forming and popularising these new ideas e.g. Galileo and Descartes.

The main theory of the day, with regard to physical science, was Atomism. Atomists believed that bodies are made from minute particles. Further, they believed that the particles and the bodies made from them, possess primary and not secondary properties. The most important exception from this viewpoint was that of Descartes. Although he rejected atomism, he did agree that bodies only really possess primary qualities. Basically what this means is that bodies in themselves possess shape, size, motion and impenetrability but not colour, sound, taste, hardness or smell. This latter group of qualities are sense dependent e.g. colour is generated in the mind through the eye. The crucial point is that since these secondary qualities are a vital component of the way we experience the world, it naturally follows that the world of experience is quite different from the world as described by science. Further, not only are these worlds different qualitatively, but they are located in different realms. If we accept that the things of which we are immediately aware possess secondary qualities and that these secondary qualities exist only 'in the mind', then what we are aware of are, 'ideas in the mind', not objects in the external world. Therefore, although these ideas of which we are aware can be held to represent, and in terms of primary qualities, resemble, objects in the world, they also constitute a 'veil of perception' which stands between the perceiver and the external world. From this we can conclude that the external world, as investigated by science, is different from the experiential or phenomenal realm.

One of the important things we must be clear about when taking about Idealism is the term 'idea' itself. As used by Berkeley and Locke the term 'idea' does not have its normal sense. We tend to think of ideas as things that are thought, and indeed ideas are considered to be close to concepts. John Locke, however, defined an idea as 'whatever is the object of the understanding when a man thinks' and he included sensations and sensory images amongst ideas. By adopting the term 'idea' for all mental objects Locke declared his intent to assimilate the intellectual and the sensory to each other, and to make the sensory the model for both. If we accept that we are directly aware of ideas in the mind and not of external things, it becomes pressing to prove that there are really any external things at all.

Descartes, in an attempt to highlight the possibility that there may be no external world, suggested that our experience might be the product of an evil demon whose intent was to deceive us. In an attempt to refute such sceptical possibilities Descartes tried to prove, a priori, the existence of a good God. Descartes argued that such a good God would not deceive us, nor allow us to be deceived, in something so fundamental as our belief in the external world. However, Descartes's proof of the existence of God was not generally accepted, even amongst theists. Although none of the major seventeenth century philosophers were sceptics, this new philosophy, having no convincing refutation of scepticism, encouraged it amongst its readers.

Allied to the fear of scepticism was the fear of materialism and atheism. The combination of Atomism and Newton's mechanistic and thus deterministic view of the world created major difficulties in understanding how it was possible for immaterial spirits such as God or the soul, to be related to the physical world. The principal difficulty was in understanding how a material and immaterial substance could causally interact. Descartes, with his proposal that the interaction of mind and body took place in the pineal gland in the brain, failed to gain much credibility. The result of this unease felt about interaction was that a materialist theory of the mind seemed preferable.

Now, common sense seems to cling on to two principles, one is that we are directly aware of physical objects and the other is that physical objects are independent of us and exist outside our minds. The dilemma produced by the 'new philosophy' makes it impossible to hold both of these principles. If we are directly aware of ideas in our minds and not of the external world, then our naive realist understanding of perception cannot be maintained. So Locke, who typified the new philosophers, abandoned Naive Realism in favour of Representative Realism. Berkeley, however, was adamant that he held on to the notion that we are directly aware of the physical world itself, while at the same time accepting that what we are aware of must be mind-dependent ideas. He concluded that the physical world consists essentially of ideas in our minds — that is esse est percipi : for material objects, to be is to be perceived. Berkeley therefore, rather than abandon direct realism, chose to modify the principle of the mind-dependence of the physical world. According to Berkeley, the mind independence of objects is not absolute, but relative. Unlike a hallucinatory object, a physical object is not dependent on the perception of any given person, and in that sense, is mind independent. But Berkeley denies that anything exists outside all minds taken together. The physical world consists of those patterns of experience that are available to all, therefore metaphysical mind-independence is not needed to guarantee objectivity. But here we have a problem — if the world is just experience, then the origin of experience can no longer be explained by the interaction of the subject and the mind-dependent world. Berkeley then thought the natural explanation was that God, instead of creating a mind-independent world which then produces experiences in us, produces the experiences directly, and these experiences are deemed to constitute the physical world. According to this model we are directly acquainted with the physical world, thus removing the barrier that made scepticism a temptation, and God is made essential to the existence of the world at every moment.

We can now show how it is possible to present Berkeley's main point as a syllogistic argument :

  1. Physical things, such as trees, dogs and tables are things perceived by sense.
  2. Things perceived by sense are ideas.
  3. Therefore, physical things are ideas.

If one objects that the first premise is false, Berkeley in reply would challenge the objector to point out one example of something that is not sensed. The only way to identify such an example is through some sensation, either by sight, touch, taste or hearing. In this way, any proffered counter example becomes an example of Berkeley's point.

If one objects that the second premise of the syllogism is false on the grounds that people sense things, not ideas, Berkeley would reply that there are no sensations without ideas and that it makes no sense to speak of some additional thing which ideas are supposed to represent or resemble. Unlike Locke, Berkeley does not believe that there is anything 'behind' ideas in a world external to the mind. There could not be. If the alleged external objects, of which ideas are supposed to be representations, exist, then they are themselves either ideas or not. If they are ideas, then Berkeley's point that everything perceived is an idea is vindicated. If they are not ideas, then they are unperceived; in particular, they would be invisible colours, intangible textured things, odourless smells and silent sounds. If someone objects that he can imagine trees or books in a closet unperceived, Berkeley would reply that this proves nothing except that there are imagined trees and books. People who think that there are unperceived objects are deceived because they do not take into account their own thinking of the allegedly unperceived object.

A criticism of Immaterialism is the question of how we deal with hallucinations and dreams. If all we ever experience is our own ideas, how can we distinguish between reality and imagination? According to Warburton the Idealist explains this by stating that 'actual ' physical objects are in fact repeated patterns of sensory information. So that it is not just the nature of an immediate experience which identifies whether it is a hallucination, a dream, or a real-life experience, but also its relation to other experiences: the general context of the experience.

The Idealist may also have to deal with the criticism that it leads directly to solipsism.The view that 'I myself alone' exist, as a mind, since everything else is only an entity in my awareness. The Idealist might respond that the logic of Idealism allows for the existence of more than one mind. Many of the things in my mind may be there through the influence of other minds. That makes more sense than saying that the things in my mind are somehow caused by things of an entirely different nature, extra-mental things. What could those mysterious extra-mental things be like? Any positive conception I could have of them would be in terms of some form of consciousness (visual, aural, tactile, and so on).Even my conception of the extra-mental is bounded by the mental. When I talk about other minds, on the other hand, at least I know what I'm talking about. (Nigel Warburton uses examples of social emotions, such as shame and embarrassment, to demonstrate that we assume that other minds exist and that to behave consistently like a solipsist would be scarcely conceivable.). Moreover, the Idealist might continue, minds don't have to be on the same level. There can be a 'Universal Mind' that causes and maintains everything that exists. Thanks to that Mind, everything that enters your mind doesn't begin to exist only when it enters your mind. It's already in the Universal Mind. And thanks to that Mind, things don't vanish out of existence when you leave the room.

In summary, the strength of Idealism is that any characterisation of the real that we can devise is bound to be a mind-constructed one: our only access to information about what the real is through the mediation of mind. Also, what seems right about Idealism is inherent in the fact that investigating the real we are clearly constrained to use our own concepts to address our own issues — that we can learn about the real only in our own terms of reference. It is logically impossible for anyone to check to see if the contrary is the case. So, although counter intuitive, Idealism is difficult to refute.


Audi, Robert (Ed). The Cambridge Dictionary of Philosophy. Cambridge University Press.(1995). pp. 72-74.

Ibid. pp. 355-356.

Ibid. pp. 437-440

Berkeley, George. Principles of Human Knowledge & Three Dialogues. Oxford World Classics.(1999).

Britannica.com. Idealism.

Mautner, Thomas (Ed).Penguin Dictionary of Philosophy, Penguin Reference.(1996). pp.66-67.

Morton, Adam. Philosophy in Practice — An Introduction to the Main Questions. Blackwell.(1996). Chapter15 pp.426-429.

Scruton, Roger. Modern Philosophy — An Introduction and Survey. Mandarin.(1994). Chapter 3. pp. 23-25.

Warburton, Nigel. Philosophy — The Basics. Routledge.(1992). Chapter 4. pp. 103-107.