Responses to comments on ‘The Zombie Threat to a Science of Mind’

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In this month’s issue of ‘Philosophy Now’ there are three letters giving intriguing responses my article ‘The Zombie Threat to a Science of Mind’ in last month’s issue (reprinted on this blog). Below I offer some short counter-responses.

Dave Magnall from Wilmslow Cheshire.

Dave argues that the flaw with the zombie argument is that it is set up ‘within a conceptual model that implies determinism but then neglects deterministic logic.’ My zombie twin lacks consciousness, and hence lacks free will. If it behaves just like me, this implies that I also have no free will, which Dave equates with determinism. Therefore, the thesis that zombies are possible assumes the truth of determinism. But if we are assuming determinism, then everything that happened had to happen, and hence there is no scope for talking about alternative possibilities, such as the possibility of zombies. Cool argument.

I would like to make two points in response. Firstly, Dave is assuming incompaibilism: the view that free will and determinism are incompatible. There is, however, a venerable philosophical tradition known as ‘compatibilism’ according to which human freedom is consistent with a physical world where everything that happens is determined from the big bang onwards. Secondly, determinism is the view that everything that actually happened had to happen given the laws of nature and the initial conditions of the universe. The determinist is free to entertain alternative possibilities of what might have happened if the laws of nature or the initial conditions had been different, and in this context is quite free to entertain the possibility of zombies.

Matthew Rapaport from The Internet

Matthew worries that the zombie argument begs the question (in the proper sense of this term meaning assuming what you’re trying to prove rather than the currently popular corrupt use meaning raises the question), on the grounds that asserting that zombies are possible amounts to little more than a brute denial of physicalism. Matthew says ‘The mind-brain identity view is precisely the view that zombie exact duplicates are not conceivable.’

Actually, the conceivability of zombies is not straightforwardly inconsistent with physicalism. Indeed most physicalists accept that zombies are conceivable, but deny the move from their conceivability to their possibility.  Although the conclusion that zombies are possible is pretty straightforwardly inconsistent with physicalism, there are two premises leading to that conclusion (Premise 1: Zombies are coherently conceivable, Premise 2: If X is coherently conceivable, then X is possible), and each of these premises is individually consistent with physicalism. Moreover, there is a lot to be said in favour of each of these premises, which is why the zombie argument has a lot going for it!

Sheila Lockhart from Inverness

Sheila has difficulty making sense of how her zombie twin can get around the world if it completely lacks consciousness, given that ‘Using the senses without sensation would appear to be a logical impossibility.’ I think it depends what you mean by ‘senses’. The zombie receives information from the environment through it eyes, and is mechanically set up such that this information regulates its behaviour in exactly the way visual information regulates behaviour in a normal human being. In this sense the zombie ‘sees’ the environment; call this ‘thin sight’. There is another sense of ‘sight’ – call it ‘thick sight’ – according to which something doesn’t ‘see’ unless it has visual experience; obviously a zombie doesn’t ‘see’ in the thick sense. However, the zombie needn’t worry about bumping into things, as thin sight, by definition, is just as effective at getting you about as thick sight.

Perhaps Sheila thinks that this distinction between thick sight and thin sight is confused in some way, but then I think the onus is on her to explain why. Over to you.

The Author

I am a philosopher and consciousness researcher at Durham University, UK. My research focuses on how to integrate consciousness into our scientific worldview.


  1. Emrys says

    First, I enjoyed your article on zombies last month. With respect to the letter writer, another question I’m curious about is whether one needs to assume that a philosophical zombie that lacks free will must itself be deterministically understood. Unless one assumes that physicalism entails determinism, it would seem possible to allow for some measure of indeterminism within the zombie universe. The letter writer appears to assume that since zombies lack free will, they must be determined (as you mentioned), but this need not imply, I think, that anything lacking free will must be determined, since even a random system need not guarantee free will. If so, this would be another reason to deny that philosophical zombies are incompatible with alternative possibilities. Your thoughts?

    • Yes, interesting thought. I guess Dave is assuming that something cannot have free will if it doesn’t have consciousness. A fair assumption, though not entirely uncontroversial. There are some deep questions here about what aspects of mentality are possible without consciousness. I’m inclined to believe that all thought is grounded in consciousness, and so I agree with Dave that a zombie wouldn’t have free will (you can’t be an agent if you can’t think), although this is a (growing) minority view (often referred to as belief in ‘phenomenal intentionality’).

      However, perhaps we can avoid these issues. If Dave is talking about the kind of free will libertarians believe in (often referred to as ‘agent causation’), then I think it is pretty uncontentious that notion of free will essentially involves consciousness. Compaibilists have a much weaker notion of what is required for free will, and perhaps a zombie could be free if compatibilism is true (although it depends on the issues I mention above), but then this brings us back to my original concern that Dave has not considered compatibilism.

      Glad you enjoyed the article!

  2. David Nyman says

    Hi Philip

    My own view on zombies is that they simply characterise, no more and no less, the view of the world according to physicalism, if – and here I must add an emphasis – the latter is curbed strictly within the limits of its own presuppositions. What I mean is this: it’s clear that the result, to date, of our probing of the physical world, is the now almost unquestioned view that nothing we study is not entirely comprehensible as the interaction of a limited set of “fundamental” entities and events. This is true both of fundamental physics and of the “special” sciences assumed thereby to supervene on it. Hardly anyone seriously questions this now; strong emergentism would seem to find few defenders these days, in my view, justifiably so. If you want a slogan for this, it would be bottom up all the way down. All this applies of course to the conceptual entities known as (p-)zombies, but the point that’s usually lost here is that it applies equally to our own bodies and brains, provided our examination is limited strictly to extrinsic factors. As we have just seen however, these very extrinsic factors are understood as providing a complete and causally closed account of everything “physical”. Hence we seem to be led to the conclusion that we ourselves must be zombies. Indeed, anything we seek to claim to the contrary must also be fully accountable in physicalist terms, mustn’t it? And this is just as things sit with the so-called zombie, don’t they?

    But wait, we cry, we still *know* – infallibly, surely – that we’re not zombies! Don’t we? Well, physicalism – again with the aforementioned emphasis – would, or at the very least should, on the basis of its own rigorous presuppositions, deny this. No utterance or judgement on our part can stand as evidence for such private knowledge, because, ex hypothesi, all such events are already fully accounted for in purely physical terms. Notwithstanding this, even die-hard physicalists usually baulk at this point. Wait a minute, they say, there may indeed appear to be a problem but actually there isn’t one. Phew! You see, what we confusedly think of as “the mind” is just the brain. Obvious, come to think of it, they do strike us as exactly the same, don’t they, just like, let me think, the morning and the evening star. Good, that was easy, I was worried for a bit. But perhaps doubt creeps back in. Wait a bit, that might have been going a bit too far, but maybe it’s all just an illusion. Yes, that’s it, we know about illusions, don’t we. It’s like when we think we see water but of course it’s just our parched brain’s desperation for a drink. The mind is just the brain’s illusion (well, I guess that does seem a little question-begging – just a little, mind. Can brains can have illusions? Isn’t that a bit like saying that brains have minds? (No, don’t think about it, it’s all an illusion).

    Enough already. I hope it’s becoming just a tad obvious that most of this is reads like nonsense on stilts. And the reason it becomes so nonsensical almost immediately when this sort of line is pursued is that most nobody can, seemingly, avoid straying from the presuppositions of physicalism, rigorously applied. Hence the question at issue is constantly left begging. What’s the solution? Well, in my view we don’t in fact need to stray from these principles at all. Instead let’s bite the bullet and simply accept the evidence of our eyes and with that, the seemingly inescapable inference to our most fundamental explanatory framework. The behaviour of bodies, brains and all the rest of the paraphernalia of the physical world in which they are embedded (and not excluding those we are pleased to call “our own”) is fully explicable in entirely physical terms. End of. Period.

    Ok, that’s clear now. But, if something still seems to be missing, there must be something wrong with the above. But what? It seems doubtful that it could be anything to do with the physicalist account in its own terms; that’s simply too successful. But what if it were to be those very terms themselves? It’s hard to see what could be wrong with them. But it should be pretty clear by now that they leave no space – not even a tad – for the existence of anything at all corresponding to a mind. Moreover – and this is really the kicker – Ils n’ont pas besoin de cette hypothèse. Everything works just great with no such entailment. If we’re going to find a space for both mind and physics, it seems we may have to start from a whole nother set of assumptions. But we do have a sufficient motivation don’t we? After all, it seems a heavy price to pay to lose one’s mind for the sake of one’s favourite theory.

    All this is to lead us to just such another point of departure. It’s based on the work of Bruno Marchal, about whom I’ve recently posted some information. Here’s the link to his website again: I hope you’ll find it worth your while.

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