Blake Winter: Berkeley’s Arguments on Realism and Idealism

Berkeley’s Arguments on Realism and Idealism


Berkeley’s Arguments on Realism and Idealism

Blake Winter


Bertrand Russell credited Berkeley with being the first philosopher to show that the position of idealism may be held without contradiction (Russell, 1997). However, in addition to this, Berkeley also attempted to show that realism was absurd, because it required concepts which could not in fact be conceptualized (1977). From this, Berkeley concluded that idealism was not merely possible but necessary, or at least necessarily the only theory we could understand.

We will commence by defining a number of terms which will be necessary or convenient for our exposition. We will proceed to give a succinct logical version of Berkeley’s argument, in order to illustrate the precise set of assumptions which are required. We will then show that using a parallel argument the same assumptions also prove that idealism as Berkeley conceived it is also not well defined.


Let us first define realism and idealism. We will take realism to mean the ontological position that there are things which exist that are neither minds nor ideas in minds. We will take idealism to mean the ontological position that everything that exists is either a mind or an idea in a mind. We may also define solipsism to be the position that everything that exists is either me or my ideas.

A concept will be said to be concrete if it may be defined ostensibly: that is, if all its conditions may be defined by direct (positive) comparisons with collections of particulars. In other words, a concept is concrete if we may determine whether an object meets its criteria by comparing it with the minimum collection of properties held in common among some collection of ostensible particulars, but we may not use the negation of these properties, unless the negation of the property in question is something for which we also have an exemplar particular (this is what is meant by the positivity of the comparison), and nor may we use only a part of the properties which are common to these particulars. We will say that a concept which is not concrete is abstract. Note that a property may be observed, but not concrete, if all particulars have that property together with some other property so that it cannot be isolated as the minimal commonality among any collection of ostensible particulars. Let us define a concept to be thinkable if it is possible to conceptualize that concept in a meaningful fashion. A concept is unthinkable, then, if it is not thinkable.

Berkeley’s Argument Against Realism

We are finally in a position to give Berkeley’s argument. Berkeley indeed only required one assumption for his result, namely:

Assumption B: Every concept that is thinkable is concrete (Berkeley, 1977).

Although Berkeley did not explicitly phrase his assumptions this way, this assumption contains the essence of his argument (he also argued that the only observable properties are the concrete ones, which is of course essential if they are to be the only thinkable ones). We now come to our first main result.

Theorem 1: The realist concept of being cannot be concrete (Berkeley,1977).

Proof: Everything of which we are aware may be said to be. However, each thing of which we are aware involves the ‘awareness of a mind.’ This notion of ‘the awareness of a mind’ is therefore one of the (positive) properties held in common among any collection of particulars of which we are aware. Therefore it is part of any concrete concept. But the realist notion of being explicitly requires that this not be a part of its definition. QED.

Corollary 2: Under assumption B, the realist concept of being is unthinkable.

Note however that Theorem 1 does not depend upon assumption B; it holds under any set of assumptions.

This result, in any case, is what Berkeley believed that he had shown. However, the argument goes far deeper.

The Extension of the Argument To Idealism

The careful reader may have noticed that our proof of Theorem 1 in fact involved an implicit assumption, or rather, that there was something which was not well-defined. Indeed we failed to give consideration to the precise meaning of ‘awareness of some mind.’ It was this error which led Berkeley to believe that he had shown that only realist being was unthinkable, and caused him to fail to realize that his argument is in fact much stronger. Let us discover what sort of concept of being we may obtain, while restricting ourselves to simple concepts.

First, we will define a new concept. Hume and Nietzsche both argued that we cannot even conceive of the self as being (Hume, 2004; Nietzsche, 1968). All we have are these ideas, which exist for-us, but the us apart from its being for-us is not in fact thinkable. In fact, then, our only notion of the self, according to both Hume and Nietzsche, is that of this conglomerate of sensation-ideas which we have, and the only notion of being which we may have, or the only concrete notion, is the notion of ‘being an idea for-me.’ Merleau-Ponty also asserts that this is the only notion that being can have for us (2006). All of these philosophers provided a degree of argument for this, but both also allowed that we were somehow able to ‘project’ the notion of the self behind these. Therefore, it became unclear whether they actually were asserting that the notion of the self was unthinkable, or whether they were only asserting that it was never concretely encountered. In any case, we will call this conception of being the Hume-Nietzschean concept of being.

Theorem 3: The only meaning of being which is concrete is the Hume-Nietzschean version.

Proof: The proof is virtually identical to the proof of Theorem 1. Every particular of which we are aware is therefore something which is an idea for-us. Therefore the set of common properties among any collection of particulars includes ‘an idea for-us.’ But then ‘being for-us’ is in fact the only notion of being left to us that is concrete. QED.

Corollary 4: Under assumption B, only the Hume-Nietzschean concept of being is thinkable.

But note that this means that we cannot even conceive of being-for-others under assumption B. Therefore, assumption B leads us to solipsism, and not merely to solipsism but to a very limited sort of solipsism where we cannot even conceive of our own existence except in terms of our particular ideas. We have therefore shown

Theorem 5: Assumption B leads to the sort of solipsism defined in the previous paragraph being the only thinkable ontological theory.


Now that we have shown where assumption B leads, let us discuss the consequences of this fact (Theorem 5).

We may, if we wish to do so, retain assumption B and accept the form of solipsism that we are left with. Of course, by doing so we do not assert that this sort of solipsism is correct, but only that it is the only sort of thing we may think of and describe.

However, this sort of a result will seem rather unpleasant to most philosophers. It follows that we must reject assumption B in favor of some other postulate. If we reject assumption B, then there is no reason why idealism is unthinkable. However, rejecting assumption B results not merely in the possibility of idealism being thinkable, but also in the possibility of realism being thinkable. We are therefore left with the following question: is it possible to nonetheless assert that idealism is thinkable, but not realism?

The answer is, of course, yes. However, this ‘yes’ has a certain caveat, in that while it is certainly possible to make such an assertion, the price of the assertion will be high. For example, let us say that we allow ourselves a certain degree of negative comparison in order to speak of being-for-others as well as being-for-us. If we do this, it is unclear why this sort of abstraction is permissible, but the similar abstraction to the being-in-itself of realism is not permissible. Similar considerations apply to other methods of obtaining a definition for being-for-others. If we wish to also think of minds existing in-themselves, it becomes even further muddled why only minds should have this privilege. Therefore, such an assertion as a Berkelian philosopher might like make becomes a seemingly arbitrary one. Whereas assumption B has a certain elegance to it which gives it some appeal, we have now descended into ad hoc assumptions designed solely for the purpose of retaining the consequence of Theorem 1.

However, whether or not it is logically possible to remain a Berkelian idealist (in the sense of holding to idealism and also denying the thinkability of realism), a more relevant question might be whether or not this is in fact true. Obviously we cannot discover this through simple logical analysis. The question before us is two-fold. First, it asks us whether or not the concepts which are components of idealism are thinkable, and second, it asks us whether or not the concepts which are components in realism are thinkable. Now we cannot answer this question by simply asserting postulates, unless we first have verified these postulates by phenomenological investigation.

It therefore follows that the ultimate test of the thinkability of both idealism and realism, and indeed of any concept of theory, lies in the phenomenological consideration of our own conceptualizations. In the opinion of the author, obtained through phenomenological studies of his own concepts, both are in fact thinkable. However, the concepts of being-for-others and being-in-itself are not concrete, and nor are they reducible. That is, they cannot be defined by taking a collection of simpler concepts and joining them together. Indeed, they must be conceived directly, through a conceptual leap, and not through any concrete derivation. For this reason, it is impossible to communicate what being-for-others or being-in-itself are. This should not be surprising: we cannot communicate the concept of redness to another, but no one will try to assert that this is an empty concept. In fact it will be seen, without much difficulty, that we in general communicate by assuming that there are certain irreducible concepts in common between us. However, a discussion of this lies beyond the scope of this paper; some work in this area may be found in (Wittgenstein, 2001).

We may give a description of two processes of conceptualization which may lead to the realization that realism is thinkable. One method has already been hinted at. If it be granted that there is some nontrivial method by which we conceptualize the other used in idealism (where by ‘nontrivial’ we mean that it is not simply the case that this concept comes to us as if it were an inborn idea), then this same method may be applied to abstract our way to the concept of things-in-themselves. The other method depends upon the concept of causation-for-us (which some have denied, but which is discovered by us phenomenologically in the author’s opinion). By abstraction from this causation, as well as from objects-for-us, it may be easier to conceive of a causally-acting object without reference to the for-us. However, in both cases, a leap is eventually required in order to conceptualize being-in-itself. It should also be observed that merely having successfully conceived of the concept, it by no means follows that the concept is applicable to any actual entity.

It should be noted that whenever we make an abstract conceptualization, we do tend to also have a sensation-image of some particular exemplar. This, perhaps, was what led Berkeley, Hume, and the other skeptical empiricists to deny that we have abstract conceptions at all. Similarly, they looked for notions such as causation occurring without themselves, in, for example, the motion of the arm (Hume, 1999; Nietzsche, 1968). It is no wonder, then, that they failed to see an exemplar of the concept. To find exemplars of causation it is necessary to begin by looking inside the mind itself, and the relation of the mind to its sensations and ideas. However, a detailed phenomenological exploration of these matters would take us too far afield; for a more detailed discussion of the phenomenology of causation (and the associated methodological errors of the skeptics in this regard) the interested reader may consult (Whitehead, 1978). In a similar fashion, perhaps it is possible to see this concept of being-in-itself as a component within ostensible particulars (this would make it possible to have epistemic certainty that they did, in fact, exist in-themselves). Nonetheless, the concept would not be concrete, since according to realism, that concept would be exemplified by all particulars, and all observed particulars also exemplify the concept of being-seen-by-me, as we have discussed. In particular, from the definition of being-in-itself, it is quite clear that everything we apprehend exists in-itself (if that concept has meaning), since that form of existence contains that of being-for-us; therefore those things we apprehend exist in-themselves, and are-in-themselves for-us.


We set out to consider the full implications of Berkeley’s argument against the thinkability of realism (1977). We have shown that this argument in fact denies not only the thinkability of realism, but also of idealism, and in fact restricts us to the Hume-Nietzschean type of being as the only thinkable kind. It follows that any attempt to maintain Berkeley’s result must use an assumption which is weakened, but we have argued that such a weakening is quite inelegant unless it also permits the thinkability of realism.

However, the ultimate decision of this issue must depend solely upon consideration of what we phenomenologically find in our conceptualizations. This unfortunately is not the sort of study that can be logically proven from one person to another. Nonetheless, we have suggested that both realism and idealism are fully thinkable.



SUNY at Buffalo

Buffalo, New York

About the Author


Berkeley, G. The Principles of Human Knowledge. London: Collins-Fontana, 1977.

Hume, D. A Treatise of Human Nature. New York: Oxford University Press, 2004.

Hume, D. An Enquiry Concerning Human Understanding. New York: Oxford University Press, 1999.

Merleau-Ponty, M. Phenomenology of Perception. New York: Routledge Classics, 2006.

Nietzsche, F. The Will to Power. New York: Vintage Books, 1968.

Russell, B. The Problems of Philosophy. New York: Oxford University Press, 1997.

Whitehead, A. N. Process and Reality. corr. ed. New York: The Free Press, 1978.

Wittgenstein, L. Philosophical Investigations. Malden: Blackwell Publishing, 2001.