Socios del Comité de Apoyo a los Corredores Biológicos

So then sensations differ from the beliefs with which they are associated. For the reasons given earlier they differ also from the desires to which they give rise. A hot pain in the toe and a cold pain in the toe are both such that we desire them to cease, but they differ from each other in the quality of the sensation. Two distinct patterns of auditory sensations may be equally pleasant, and so on. More obviously, sensations are distinct from thoughts, and from purposings. My having a yellow sensation is distinct from my thought that I am having a yellow sensation; if it was not, the thought would have no content; there would be nothing about which it was making a claim. And a sensation is a passive event, something that happens to an agent, not his trying to do something—and so not a purposing.

Once the distinctness of sensations from mental events of other kinds, and especially from beliefs and desires, is recognized, the temptation to give a behaviourist account of sensations should vanish. By a behaviourist account of some apparently mental event I mean an analysis of it in terms of the public behaviour which follows certain stimuli. In

The Concept of Mind Gilbert Ryle discussed the concept of intelligence.30 He argued that to say that some man is

intelligent might seem to be ascribing to him some very private mental property. But when we think about it, we realize that to say that a man is intelligent is to say that he answers difficult questions quickly, usually gets the answers right, draws our attention to problems which we had not noticed, avoids courses of conduct which will prevent him from obtaining his goals (courses which most of us would not notice were unsatisfactory). And so on. In all these ways a man's being intelligent is a matter of how he does behave publicly (‘answers’, ‘draws attention’, ‘avoids’); and how he would behave if circumstances were different (not merely does he get right the answers to actual questions; but we have reason to suppose that this is no accident, because he would have got right the answers to different questions, if they had been put). There is some initial plausibility in such a behaviourist account of intelligence. There is also some initial plausibility in a behaviourist account of belief. Is not to believe that John is my friend to ‘act as if’ he is my friend?

I do not believe that a behaviourist account of belief will work, and I will give my reasons in a later chapter. I am not even very sympathetic to a behaviourist account of intelligence. But behaviourist accounts of these mental concepts have more plausibility than a behaviourist account of sensations. Ryle, notoriously, did not give one in The Concept of

Mind.

Armstrong's attempt to get rid of sensations had as its first move his attempt, which I have argued to be unsuccessful, to show that sensations are really acquisitions of belief or inclinations to acquire a belief. Armstrong then went on to argue that beliefs are simply states of brain apt to produce certain kinds of behaviour in certain circumstances. His is not quite a behaviourist theory because it equates beliefs with the brain-states which produce certain

behaviour rather than with the behaviour itself. But the difference is not a very great one. However, once it is clear that sensations are distinct from beliefs, this kind of approach cannot even get started, and the initial implausibility of a behaviourist account of sensations stands apparent.

On a behaviourist account, for a subject to have a red image would be for him to react publicly in the sort of way in which people react to ripe strawberries and tomatoes, British pillar boxes and labour party badges, viz. to say that he has an image of the same colour as they, if he is asked and if he has the purpose of telling the truth. But of course he may not have the purpose of telling the truth on this matter (a fact which may not be revealed by his public behaviour) and so his red image may not affect his behaviour at all. And even if it does, maybe he has, relative to others, an inverted colour-sensation spectrum, of the kind which we considered earlier, and what he calls ‘red’ looks to others the way blue things look to him, and conversely. I argued earlier that this sort of thing is not empirically very likely, but it could happen, and if it did, the subject's public behaviour would be exactly the same as if his colour-sensation spectrum was normal, for he would classify objects in the same way. Or again maybe the subject is a robot without any sensations at all, but programmed to react publicly to light-waves in the same way as those who do have sensations. There is more to having a sensation than public behaviour of the kind normally caused by stimuli from objects of certain kinds.

These are old points and, I hope, obvious points. They are only likely to be obscured if you come to think that sensations are the same as beliefs, which you may begin to do if you think that they are incorrigible foundations of knowledge. That is why I have devoted quite a lot of his chapter to distinguishing between sensations and beliefs. Hard materialism, to repeat, is the doctrine that there are no mental events (the instantiation of mental properties, ones to which the subject has privileged access) but that all talk about events which are apparently mental, such as sensations, is really talk about physical events. There are two forms of hard materialism—behaviourism which claims that talk about apparent mental events is really talk about public behaviour; and mind/brain identity theory which claims that talk about apparent mental

events is really talk about brain-events. I have argued in this chapter that behaviourism is false because it cannot deal with sensations. In the next chapter I shall argue that mind/brain identity theory is false, because it, too, cannot deal with sensations.

3. Sensations and Brain-Events

I argued in the last chapter that sensations are distinct from public behaviour. A man's having a red image or feeling a pain is not his behaving in certain public ways under certain public circumstances. I now wish to argue in this chapter that sensations are distinct from brain-events. The brain consists mainly of billions of nerve-cells, neurones, which transmit to neighbouring neurones electrical charge by ‘firing’, that is undergoing a sudden change of electric potential which is transmitted across the gap between the neurones by a chemical transmitter. I shall argue that goings-on in his brain may cause and may be caused by a man's sensations, but they are not the same as them. Just as the ignition of a fuse is distinct from the explosion which it causes, so, I shall be arguing, firings of neurones are distinct from the visual sensations or pains which they cause.

Mind/brain identity theory claims otherwise. It claims that every sensation (and every other apparently mental event) is really identical to some brain-event. The last twenty five years has seen an explosion of philosophical writing elaborating and defending mind/brain identity theory, and there are many subtly different variants of the theory.31 I

shall not discuss the different variants in detail; but hope that the arguments which I shall marshal will be conclusive in showing that (whatever might be the case with beliefs, desires, or other apparently mental events), sensations are not brain-events.

For the purpose of assessing identity theory, I shall allow the identity theorist a crucial assumption—that persons are simply material objects; that there is no more stuff to persons than the

31 _{Beginning with the famous papers by U. T. Place in 1959 and J. J. C. Smart in 1962. These early papers and subsequent important papers arguing for and against identity}

theory published over the next decade are contained, among other places, in (ed.) C. V. Borst, The Mind/Brain Identity Theory, MacMillan, London, 1970 . The best-known full-length defence of identity theory (other than those which I shall discuss in detail later) is D. M. Armstrong, A Materialist Theory of Mind, Routledge and Kegan Paul, London, 1968.

matter of which they are made. It is an assumption which I shall see reason later in the book to reject, but it is one which identity theory inevitably makes. Events (see Chapter 1) consist in the instantiation of properties in substances. Physical events consist in the instantiation of physical properties. A physical property is one such that no one person is necessarily better placed to know that it is instantiated than is any other person. Brain-events, as discussed by identity theorists, are supposed to be physical events.

The question of whether sensations are identical with brain-events, then boils down to the question whether the instantiation of sensory properties (e.g. having a red image) in the material object which is a person is a different event from the instantiation of any physical brain property (e.g. having certain groups of neurones, let us call them C-fibres, fire) in that person. Just as a disc being round is a different event from its being red, and a jelly being transparent is a different event from it being circular or tasty, is my having a red image or a headache a different event from any brain- state? Are these are connected events, or just one?

Identity theory draws our attention to the fact that the same event can be described in different ways—my writing Chapter 3 of The Evolution of the Soul and Richard Swinburne writing the chapter about identity theory in the book of his Gifford Lectures. Identity theory claims that that is how it is with my being in pain and my having certain specified nerves fire;32 the same event is described in two different ways.

In order to discuss properly whether sensations are brain-events, I shall need to consider first the very general question of when two events are the same, or rather of when an event described in one way is the same event as an event described in another way. And in order to discuss that question, I need to discuss a prior question—when are two properties the same, when do two words ‘P’ and ‘Q’ pick out the same property?