To: Christian M.
From: Geoffrey Klempner
Subject: Berkeley on abstract ideas and unperceived objects
Date: 5 September 2007 12:10

Dear Chris,

Thank you for your email of 27 August, with your response to my comments on your essay on Berkeley on primary and secondary qualities, and your two new University of London essays, 'What, according to Berkeley, is wrong with the theory of abstract ideas?' and ''What more easy to conceive a tree or house existing by itself, independent of and unperceived by any mind soever?' How does Berkeley reply to this challenge?'

There's a very useful paper by Anthony Grayling, 'Berkeley's Argument for Immaterialism' at http://www.acgrayling.com/articles.html Grayling emphasises the importance that Berkeley places on the principle that the existence of x requires that x is actually perceived.

One point worth making is that when a philosopher has a well-articulated theory, as Berkeley does, we should not assume that there is one, and only one, canonical way to argue for the theory. A philosophical argument is simply something that takes you from something you accept to something you wouldn't have accepted without argument.

Abstract ideas

Given that the rejection of abstract ideas is part of Berkeley's attack on the idea of 'matter' (although not necessarily the premise, cf. above), it should nevertheless be possible to examine the critique of abstract ideas in its own right, apart from any application that is made of it. That is what this essay question is asking for.

It's OK to give matter as one example of an abstract idea (and hence, an example of what is wrong with abstract ideas) but that's as far as you can reasonably go.

Reading your essay, I gather that for Berkeley what Locke would term an 'abstract idea' is a particular idea which is 'general in its signification'.

But what exactly is the difference between saying that I have an idea of 'cat' which can apply to any cat by ignoring particular features, e.g. size, colour, and that I have an idea of 'cat' which contains only those features which are possessed by all cats (e.g. having parents which are cats)?

Hume thought that the rejection of abstract ideas was a 'great discovery'. What is so great about it?

You mention nominalism. One possible motive is Occam's Razor. Armed with a suitable notion of 'resemblance' you don't need any other concept (a point made by Russell). But why is that an advantage? Is it possible that Berkeley didn't realize that the one 'abstract idea' that you can't get rid of is the idea of resemblance?

It is worth noting that the notion of an 'abstract idea' is not equivalent to the doctrine of 'abstractionism' (as criticized by Geach in his book 'Mental Acts'), the Lockean view that we form concepts by seeing what is common in a set of particulars. Critics of abstractionism argue that we need language - i.e. concepts/ ideas - in order to 'perceive what is common'. Is it possible that Berkeley is dimly aware of this point, but chooses the wrong way to express it?

Unperceived existence

How Berkeley immediately replies to this challenge is in his notorious argument that when we conceive of the house or the tree, we conceive of it as the object of the perception of some observer. So the notion of 'unperceived existence' is an absurdity.

Critics of Berkeley have fastened on this as an obvious fallacy, wrong taking this to show that there is nothing more to Berkeley's immaterialism than fallacious or sophistical reasoning. If I were writing this essay, I would use that as a starting point for the other, more substantial arguments that you examine.

We are both agreed (I take it) that there is much more to Berkeley's attack on matter. My view would be that the central argument (not at all apparent from Berkeley's text) is that 'eliminating matter from our ontology nothing happens'.

You need to be careful about how you bring in God. We are agreed that God is required for Berkeley's theory to be adequate, but this is something which would require further demonstration, beyond the demonstration of the incoherence of the idea of 'a tree or a house existing unperceived'.

All the best,

Geoffrey