To: John D.
From: Geoffrey Klempner
Subject: Kant's second 'Refutation of Idealism'
Date: 6 September 2007 11:34

Dear John,

Thank you for your email of 30 August, with your essay for the Metaphysics program in response to the question, 'Give a careful account of the argument of Kant's Second 'Refutation of Idealism'.

This is not a bad piece of work. You are puzzled by things that you should be puzzled by. However, I am not sure whether reading this account I would be persuaded to embrace the conclusion that Kant intends. Perhaps you yourself are not fully persuaded.

I remember as a graduate student studying Kant, coming to the conclusion that Kant did not fully grasp the force of his own argument. (For the sake of balance, I have to say that my supervisor at the time, P.F. Strawson, did not fully agree with me.)

Apart from Berkeleian idealism and Cartesian 'problematic idealism' there is a third target which Kant does not even bother to name, but which (I would argue) is the real target: namely, naive subjectivism, the view that all that exists, is a stream of experiences which I am experiencing. Not only can I not prove that anything else exists (as Descartes tries to do), I can't even *make sense* of the idea of an entity or object which is not an experience of mine.

Berkeley's solution is to make experience or 'ideas' something which exists independently of me, in the mind of God. That is how he establishes a notion of objectivity without recourse to the idea of 'matter'.

Kant's objection to Berkeley is that the very ideas of 'matter' and 'space' are constitutive of experience. It is not an accident that I seem to perceive objects in space (even though, according to Berkeley I am really looking at the inside of God's mind). There is no other form that experience can take. The real error of Berkeley, as it turns out later, is his attempt to picture 'things in themselves' on the analogy with things we experience ('ideas' in God's mind are like our 'ideas').

This is the clue to something that puzzled you, Kant's remark that 'This idea of permanence is not itself derived from external experience.' The point of the Transcendental Deduction is to establish that the ideas of causality and permanence cannot be derived empirically from experience (as Locke thought) but rather are an a priori condition for the possibility of experience. In other words, if our minds did not operate with the notions of causality and permanence, then we would not be capable of experience anything at all.

But why? Surely, I can imagine a stream of experiences, spread out in time, where nothing is permanent, nothing causes anything or is caused by anything? What's wrong with that? That is what the naive subjectivist believes. I know an experience when I have it. There's nothing more to say.

Kant's answer is that I have no right to use the word 'I'. To say that I have an experience X followed by an experience Y assumes that one and the same 'I' has experiences X and Y. This is how the time order is established. But there is no basis for making such a claim. Things would be just as they are now if experience Y ('my' present experience, along with an apparent memory of previous experiences) is the only thing that has ever existed in the history of the universe.

The Refutation of Idealism solves this riddle by linking self-knowledge to knowledge of the world around me. The two stand or fall together: either I have knowledge of the world around me, and of myself as one of the entities that traverse a path through the world, or I have neither knowledge of the world around me, nor of my own self.

You can see how Kant (correctly) interprets this as a response to Descartes. Descartes believed that knowledge of the external world can be established only by first proving the existence of a non-deceiving God. What he fails to reckon with is that knowledge of the external world is already presupposed in the certainty of the cogito.

However, the real target, as I indicated above, is the subjectivist who refuses to go even as far as Descartes. While Descartes is prepared to accept that an external world 'might' exist (depending on whether he is being deceived or not), the subjectivist declares that the very idea of anything existing outside my own mind is self-contradictory and absurd.

One aspect of Kant's Refutation which you don't mention, but which I think you should have been puzzled by is Kant's concession that I might, after all, be dreaming that I am writing this email to you. According to Kant, whether I am dreaming or not is a matter of inductive judgement, based on the coherence of my present experience with past memories etc. etc. If Daleks were to appear in my study threatening to exterminate me, or if I seemed to wake up in a pod in the Matrix world, I might revise that judgement. But in that case, how is this knowledge? No matter how coherent my experience appears, everything can still be overturned in the next moment.

This worry is not Descartes' worry that there might not exist an external world of objects in space *at all*, but rather scepticism about how things actually are in the physical world. But that's still a pretty scary thing to be sceptical about.

All the best,

Geoffrey