Jean Hogan: When Dr Johnson kicked the stone

What did Dr. Samuel Johnson hope to accomplish by kicking a stone? Did he succeed in proving a valid point against Berkeley?

After we came out of the church, we stood talking for some time together of Bishop Berkeley’s ingenious sophistry to prove the nonexistence of matter, and that every thing in the universe is merely ideal. I observed, that though we are satisfied his doctrine is not true, it is impossible to refute it. I never shall forget the alacrity with which Johnson answered, striking his foot with mighty force against a large stone, till he rebounded from it — “I refute it thus” (Boswell 25-26).

Samuel Johnson’s dismissal of George Berkeley’s metaphysics was too quick at best, misguided at worst, and ineffective either way. In this essay I will show that Berkeley’s system is strong and flexible enough to counter most objections. Some of Berkeley’s arguments do have weaknesses, to be sure, but Johnson neither exposed nor engaged with these by simply kicking a stone.

Berkeley’s metaphysical position is usually known as “idealism” – that is, the view that reality consists exclusively of minds and their ideas – or, because of what it denies, “immaterialism”. “Materialism” is here understood as the theory that material things exist, with “material things” being mind-independent things (or substances). A mind-independent thing is something whose existence is not dependent on thinking/perceiving things, and thus would exist whether or not any thinking/perceiving things (that is, minds) existed. Berkeley’s striking contention was that no material things exist.

A point worth emphasizing at the outset is that, even though there was no material world for Berkeley, there was a physical world, a world of ordinary objects. Berkeley did not deny the existence of common objects, such as stones, trees, and apples (24-25). But on Berkeley’s account, such objects are bundles or collections of ideas.[1] An apple, say, is a combination of visual ideas – including the sensible qualities of colour and visual shape – of tangible ideas, ideas of taste, smell, and so on. Berkeley himself was most insistent on this point: There is no need to deny that stones, trees, and apples exist but only to stress that they are the very things we perceive – which is to say that they are mind-dependent ideas. Their esse (being) is percipi (to be perceived).

Thus Johnson neither did nor could disprove Berkeley’s idealism – and thereby prove the existence of matter – by kicking a stone. Indeed, Johnson’s reaction seems to be based on a misunderstanding: The word “idealism” has different meanings both inside and outside philosophy. When employed philosophically, “idealism” occasionally suggests the denial of common objects. Berkeley is sometimes – wrongly – taken to be an idealist in this sense, and Johnson was possibly under this misapprehension. Yet Berkeley was an idealist in the perfectly straight forward sense, of holding that mind constitutes the ultimate reality, and everything else that exists consists in its being perceived.
It is crucial to understand Berkeley’s use of the word “idea” in order to understand his thesis. In Berkeley’s sense of the word, an idea is anything that is immediately known, as sense-data for example are known. Berkeley proved by arguments that are largely valid that our sense-data cannot be supposed to have an existence independent of us but must be, in part at least, in the mind – in that their existence would not continue if there were no seeing or hearing or touching or smelling. Thus a particular colour we see is an idea, as is stone that we touch (or, in Johnson’s case, kick), and so on. There are also things remembered or imagined, because we have immediate acquaintance with such things at the moment of remembering or imagining. For Berkeley, all such immediate data were “ideas”. Since it was a philosophical commonplace at the time to treat the immediate objects of perception as ideas, there is nothing surprising in Berkeley’s adopting this standpoint as well.

In other words, Berkeley presupposed that each of us is aware only of the ideas (the “sensations” or “perceptions”) that are somehow or other produced in our minds. On the most common view – that taken by Rene Descartes, John Locke, et al. – ideas are produced in us by external objects, which objects we do not perceive immediately because, in words of Locke “the Mind… perceives nothing but its own Ideas” (qtd. Craig 97, Locke’s emphasis). Berkeley’s insight was that, if we differentiate the “ideas” we perceive from the “real” objects that lie hidden behind them, scepticism becomes inevitable. At best we can hypothesize the existence of real objects as the most likely causes of our ideas, but we are then vulnerable to the suggestion that there could be other causes, such as an omnipotent god. Moreover, and as materialists must admit, we could have our ideas without there being any external objects causing them. As materialists must also admit, the existence of matter does not help to explain the occurrence of our ideas. The basic problem here is set by dualism – i.e. the problem of how one substance can causally affect another substance of a fundamentally different kind; the problem of how an extended thing which affects other extended things only by mechanical impact can affect a mind (which is non-extended and non-spatial). Motivated by these difficulties with the materialist alternative, Berkeley argued that only an immaterialist account of objects can avoid scepticism about their existence and nature.

Berkeley next considered common objects: He showed that all we know immediately when we perceive a tree, say, consists of ideas – and this premise was accepted by all the modern philosophers. Berkeley proceeded to argue that there is not the slightest ground for supposing that there is anything real about the tree except what is perceived. Sense-data are the only things of whose existence our perceptions can assure us, and to be known is to be in a mind – and therefore to be mental. Berkeley concluded that nothing can ever be known except what is in some mind, and whatever is known without being in my mind must be in some other mind (or, rather, Mind).[2]

There are fallacies in Berkeley’s arguments. For example, confusion is engendered by the word “idea”. We think of an idea as essentially something in somebody’s mind, but the notion of being in the mind is ambiguous. When I speak of bearing a person in mind, I do not mean that the person themself is in my mind but that a thought of them is in my mind. When I say that the appointment I had to arrange went out of my mind, I do not mean that the appointment itself was ever in my mind, only that a thought of it was formerly in my mind and then ceased to be. And so, all Berkeley really had a right to say was that a thought of the tree must be in our minds. This confusion might seem too crass to have been really committed by any competent philosopher, but Berkeley’s view – that the tree obviously must be in the mind – seems to depend for its plausibility upon confusing the thing apprehended with the act of apprehension. Either of these might be called an idea, and either probably would have been called an idea by Berkeley.

Fallacies like that outlined above have been important in the history of philosophy. But then Johnson neither exposed nor engaged with the weaknesses in Berkeley’s argumentation by kicking a stone – a stone whose existence Berkeley would not have denied, for the distinction between real things and ideas retains its full force on his view.


1. Berkeley did not address in detail the philosophically interesting question of what does the combining. He did however make it clear that there are two sides to the process of bundling ideas into objects: 1. Co-occurrence, an objective fact about what sorts of ideas tend to accompany each other in our experience, and 2. Something we do when we decide to isolate a set of co-occurring ideas and refer to it with a certain name (An Essay 109).

2. Berkeley allows that the tree continues to exist when we shut our eyes or no human being is near it. This continued existence is due to fact that God continues to perceive it. In other words, the tree consists of ideas in the mind of God – ideas that are more or less like our ideas when we perceive the tree but differ in that they are permanent in God’s mind so long as tree continues to exist. As such, all our perceptions are a partial participation in God’s perception. It is because of this participation that different people see more or less the same tree.


Boswell, James. The Life of Samuel Johnson. Munich: BookRix, 2014.

Berkeley, George. An Essay Towards a New Theory of Vision. The Works of George Berkeley, Bishop of Cloyne. Ed. A. A. Luce and T. E. Jessop. London: Nelson. 1: 171-239.

—. Principles of Human Knowledge and Three Dialogues. Oxford: OUP, 1999.

Craig, Edward (ed.). The Shorter Routledge Encyclopedia of Philosophy. London: Routledge, 2005.

Downing, Lisa. “George Berkeley”. The Stanford Encyclopedia of Philosophy (Spring 2013), Ed. Edward N. Zalta.

© Jean Hogan 2018