Mind Association

Zombies, Schizophrenics, and Purely Physical ObjectsAuthor(s): Don LockeSource: Mind, New Series, Vol. 85, No. 337 (Jan., 1976), pp. 97-99Published by: Oxford University Press on behalf of the Mind AssociationStable URL: http://www.jstor.org/stable/2253259 .

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Zombies, Schizophrenics, and Purely Physical Objects

DON LOCKE

Strolling one day through the pages of Mind I came across a curious individual called Dan (see R. Kirk, 'Sentience and Behaviour', Mind LXXXIII, January 1974). When I administered him a playful kick on the shins he grunted, doubled over, rubbed his leg-and then hissed through clenched teeth, 'I really don't know why I'm doing this; honestly I didn't feel a thing. I never feel pains at all these days, though I continue to react as if I did. What on earth is wrong with me?'. Here, I thought, is a case for my friendly neighbourhood Materialist.

'Some people will tell you', the Materialist said, 'that Dan provides a counter-instance to Materialist theories of mind, and even to the Principle of Sufficient Reason. But if it is allowed that all human be- haviour is fully explicable in physico-chemical terms, as we believe, then naturally both aspects of Dan's behaviour-both his pain-behaviour and his anti-pain behaviour, so to speak-will be so explicable. And this explanation could turn out to be of either of two kinds. It might be that his brain is found to manifest the neural activity which characteristically mediates between pain-causes and pain-reactions, but also manifests in addition unusual patterns of neural activity which are responsible for his perplexing anti-pain behaviour. In that case the correct diagnosis of Dan's complaint is not, as he claims, that he has ceased to feel pains, but that he is in a state of pain-schizophrenia, where he at once feels pains and yet also sincerely denies that he does'.

'But that means', I interrupted, 'that if Dan progresses in the way outlined by Dr. Kirk, so that this curious ambivalence extends step by step over all the varieties of sensory experience, but accompanied by a gradual decrease in his willingness, or even ability, to protest that he is not seeing, hearing, etc., until in the end he is to all external appear- ances exactly like a normal person once more; then the correct interpreta- tion is not, as Kirk would have it, that Dan has now become a Zombie, lacking sentience altogether, but that Dan is now a normal person once more, recovered from his strange schizophrenia'.

'Of course', replied the Materialist. 'What other interpretation would be plausible, when the extra, abnormal neural activity which once caused his abnormal behaviour has now disappeared, and his brain has returned to the normal state of normal people? And even if the case history then repeats itself in the reverse order, the appropriate diagnosis would still be a recurrence of the schizophrenia, not a return from Zombiehood to normal sentience'.

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98 DON LOCKE:

'Well', I said, unconvinced, 'Kirk certainly makes it seem more plausible to suggest that Dan has reached and returned from a state of complete Zombiehood-as Dan himself insists'.

'We can't believe everything schizophrenics tell us', the Materialist said patiently, 'and in any case there is a second possible account of what is going on inside Dan's skull during these dramatic developments. For it may be that it is the pain-behaviour, rather than the anti-pain behaviour, which is brought about by unusual brain-states replacing the usual neural activity which intervenes between pain-causes and pain-reactions. In that case the appropriate diagnosis would be that Dan really does feel no pain, just as he insists he does not, and the plausible interpretation of his case history is indeed that he is advancing to, and then recovering from, a state of complete Zombiehood. At one point Dan does lack sentience, precisely because his brain lacks the neural activity which we Materialists identify as sentience; his behaviour has other causes. And the reason why the diagnosis of Zombiehood is more plausible than the diagnosis of schizophrenia is that the case history described by Dr. Kirk looks as if it will have this second, not the first, explanation. But a priori we cannot be absolutely sure what the correct explanation will be'.

I could see there might be difficulties here for the casual analysis of mental states, difficulties dramatised by Kirk's hypothesis of a Brain Team which takes over the normal functions of the brain, but that seemed to me to raise other issues, so I simply muttered, as I turned away, 'But given the incredible complexity, variety and adaptability of the brain, can we really isolate neural patterns into normal and unusual? We are talking as if there is one specific and easily identifiable brain state responsible for each identifiable bit of behaviour, but we know it isn't really like that. So isn't it likely that there is no way of isolating a particular bit of neural activity which characteristically mediates between pain-causes and pain-reactions-indeed no such characteristic bit of neural activity to isolate-and hence no way of making the distinction between the two neurological diagnoses of Dan's problem?'. But, as I half expected, the Materialist did not hear me.

II

In a second paper, 'Zombies v. Materialists' (Aristotelian Society, Supplementary Volume XLVIII, 1974), Kirk has again appealed to the possibility of Zombies, in order to demonstrate that the Materialist, despite his constant assertions to the contrary, is committed to there being an entailment, and not merely a contingent connection, between so-called physical states, in particular brain-states, on the one hand, and so-called mental states on the other. Indeed Kirk seems to think that those materialists who appeal to a causal analysis of mind (he cites David Lewis) are already committed to this Entailment Thesis, but this appears to be a misunderstanding. Their argument is that something's being an experience or mental state is entailed by its having the appro- priate causal role, but nothing entails that the state actually having that

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PURELY PHYSICAL OBJECTS 99 causal role must be a physical, or brain, state; that remains a contingent, empirical matter. So although Kirk goes on to argue that the Entailment Thesis is false, the mere demonstration that the Materialist is committed to it would be a sufficient refutation of all extant forms of Materialism.

Kirk's argument is that the Entailment Thesis follows from the typically Materialist claim that man is nothing but a physical object. For if the connection between physical states and mental states were only a contingent one, then it would be logically possible that there be a being possessing all the physical states we possess, but lacking our mental states-a Zombie, in short. Beyond question such a Zombie would be nothing but a physical object, but since he (or it) lacks properties which we possess it seems equally undeniable that we, being more than Zombies, must also be more than purely physical objects. The only way to block this inference, and so retain the claim that man is nothing but a physical object, is to deny the logical possibility of Zombies, by insisting that the relevant physical states actually entail the relevant mental states.

Now first of all it is clear that the Materialist is committed to the logical possibility of Zomi-bies, inasmuch as he allows the logical possibility that human beings might be more than purely physical objects, might even possess Cartesian souls. So if anything has to go it will be not the contingent connection between the physical and the mental, but the claim-obscure enough, in all conscience-that man is nothing but a physical object. But the Materialist can still insist that man is in fact, though not in logic, nothing but a physical object, so long as he denies, as he does, the empirical possibility of mere Zombies. That is, he can concede that it is indeed logically possible that a being which was nothing but a physical object would be something less than a man, while still insisting that any actual being which possessed the relevant physical properties would also, as a matter of hard empirical fact, possess the so-called mental properties. Thus, as things actually are, a being which was nothing but a physical object would lack nothing that human beings possess, inasmuch as there are no properties possessed by men whose presence is not physically guaranteed, though not logically entailed, by the presence of purely physical properties. Certainly if human beings were different from what they are-if they were Cartesian, for example then men would be what Zombies are not, but as things are a putative Zombie would turn out to be a sentient human being; there would be in fact no difference between the two.

This reply, like the first, seems to me to succeed, at least as a reply to Kirk. But it also, like the first, rests on an assumption which perhaps invalidates the whole discussion. This is the assumption, questioned by D. H. Mellor ('Materialism and Phenomenal Qualities', Aristotelian Society, Supplementary Volume XLVII, I973), that a clear and useful distinction can be drawn between physical and non-physical properties in the first place. Until this is cleared up Materialism remains a more obscure thesis than I was once inclined to think that it was.

UNIVERSITY OF WARWICK

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