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Difficulties for a materialist view of the mind


To: Adam F.
From: Geoffrey Klempner
Subject: Difficulties for a materialist view of the mind
Date: 22 February 2008 12:20

Dear Adam,

Thank you for your email of 15 February, with your first essay for Possible World Machine, in response to the question, 'What difficulties stand in the way of a materialist view of the mind, according to which thoughts, feelings and sensations are ultimately nothing more than processes in the brain?'

Your effort hasn't been wasted. This is a good piece of work, which clearly shows that you have done some research and thought hard about the significance of the question.

The question refers to the difficulties facing materialism, so, strictly speaking the fact that there are also difficulties with dualism or idealism is not relevant to answering the question, as stated. Maybe there are difficulties with every theory of the relation between mind and body. So what?

You are right to pinpoint Descartes 'depiction of the mind as being a non-physical substance' which to a large extent (though not exclusively, as we shall see) defines the problem faced by the materialist.

The problem of qualia is best illustrated by a provocative argument put forward by David Chalmers. I can imagine the existence of a duplicate of GK on 'twin earth', who is physically indistinguishable from *this* GK in every way, except for the fact that 'all is darkness within'. In other words, GK's zombie double. At this very moment, GK's zombie double is sitting at a desk writing an email to his student, AF, or if you like, AF's zombie double.

We may assume that the entire story about how the email gets written, goes through the internet and gets to you has a physical explanation (in other words, we have ruled out Cartesian interactionism on the grounds that it is inconsistent with current physics). And yet, there seems to be something extra 'in' me, which has no role to play in explaining this sequence of physical events, but merely 'exists' in just the way Descartes said: I cannot doubt that, at this very moment, I have experiences corresponding to the physical processes taking place. For example, a constant hum, tapping sounds, patches of light in my visual field and so on.

The problem with this argument -- effectively, an argument for a version of epiphenomenal dualism -- is that it relies (in my view) on an illicit notion of 'private object', as attacked by Wittgenstein in his 'Philosophical Investigations'. There has been huge debate over this. What seems hard to argue with, however, is that by hypothesis my zombie double will act in every was as if it 'believes' that it has qualia too, which is a very strange result if not an outright refutation of the argument.

There is a very useful discussion of Frank Jackson's knowledge argument in the Fellowship dissertation by Samuel Michaelides which you can find on the Pathways site at, so I won't say any more about this.

These both concern what has been described as the 'hard' problem of consciousness, the sheer inexplicability of the reality of subjective experience.

The problem of intentionality, on the other hand, seems more tractable because we are familiar with the idea that a physical system can embody 'content'. This is the idea that the human brain is, essentially, no different from a computer running a 'program', a view advocated by Daniel Dennett. Even if there is no 'program' as such for the human brain -- a view held by 'connectionists' who see the brain as best modelled by a 'neural network' -- there might still be a broader sense in which mental content has a 'functional' basis, albeit one which cannot be decoded in the way that one can analyse the structure of a computer program.

It is agreed on all sides that there is, in fact, an 'explanatory gap' as you describe it. The question, however, is whether this explanatory gap merely reflects the contingent limits of human knowledge at the present time, or whether it has a deeper significance.

Thomas Nagel, in his now famous essay, 'What is it like to be a bat?' gives an argument for questioning physicalism which does not rely on Cartesian intuitions about 'one's own case', but rather stimulates our intuitions about how we view subjects who are very different from us, such as a bat. According to Nagel, physics is essentially limited by its adherence to the 'objective view'. Any solution to the mind-body problem can only come about through a new 'science' -- which at present we can barely envisage -- which would somehow bridge the gap between the subjective and objective.

Colin McGinn and John Searle both offer variations on this theme, McGinn arguing that the very nature of the human brain and the concepts we are able to form prevents us from comprehending the nature of the relation between mind and body, while Searle allows that science might yet come up with a solution, but hasn't done so yet, using his thought experiment of the 'Chinese Room', to reject the popular AI route espoused by Dennett.

I hope that some of these remarks will help you pursue the question further, when you have the time. It is a vast topic, which continues to generate thousands of books and articles.

All the best,