Philosophy

far a merely empirical fact that mnemic causation is almost exclusively associated with matter having a certain chemical structure. But the same may be said of magnetism. As yet, we cannot deduce the magnetic properties of iron from what we know of the structure of the atom of iron, but no one doubts that they could be deduced by a person with sufficient knowledge and sufficient mathematical skill. In like manner it may be assumed that mnemic causation is theoretically deducible from the structure of living matter. If we knew enough, we might be able to infer that some other possible structure would exhibit mnemic phenomena, perhaps in an even more marked degree; if so, we might be able to construct Robots who would be more intelligent than we are. In the psychological way of defining a “mind”, it consists of all the mental events connected with a given mental event by “experience”, i.e. by mnemic causation, but this definition needs a little elaboration before it can be regarded as precise. We do not want the contraction of the pupil to count as a “mental” event; therefore a mental event will have to be one which has mnemic effects, not merely mnemic causes. In that case, however, there cannot be a last mental event in a man’s life, unless we assume that it may have mnemic effects on his body after death. Perhaps we may avoid this inconvenience by discovering the kind of event that usually has mnemic effects, though they may be prevented from occurring by special circumstances. Or we might maintain that death is gradual, even when it is what is called instantaneous; in that case the last events in a man’s life grow progressively less mental as life ebbs. Neglecting this point, which is not very important, we shall define the “experience” to which a given mental event belongs as all those mental events which can be reached from the given event by a mnemic causal chain, which may go backwards or forwards, or alternately first one and then the other. This may be conceived on the analogy of an engine shunting at a junction or where there are many points: any line that can be reached, by however many shuntings, will count as part of the same experience. We cannot be sure that all the mental events connected with one body are connected by links of mnemic causation with each other, and therefore we cannot be sure that our two definitions of one “mind” give the same result. In cases of multiple personality, some at least of the usual mnemic effects, notably recollection, are absent in the life of one personality when they have occurred in the life of the other. But probably both personalities are connected by mnemic chains with events which occurred before the dissociation took place, so that there would be only one mind according to our definition. But there are other possibilities which must be considered. It may be that each cell in the body has its own mental life, and that only selections from these mental lives go to make up the life which we regard as ours. The “unconscious” might be the mental lives of subordinate parts of the body, having occasional mnemic effects which we can notice, but in the main separate from the life of which we are “conscious”. If so, the mental events connected with one body will be more numerous than the events making up its central “mind”. These, however, are only speculative possibilities. I spoke a moment ago of the life of which we are “conscious”, and perhaps the reader has been wondering why I have not made more use of the notion of “consciousness”. The reason is that I regard it as only one kind of mnemic effect, and not one entitled to a special place. To say that I am “conscious” of an event is to say that I recollect it, at any rate for a short time after it has happened. To say that I recollect an event is to say that a certain event is occurring in me now which is connected by mnemic causation with the event recollected, and is of the sort that we call a “cognition” of that event. But events which I do not recollect may have mnemic effects upon me. This is the case, not only where we have Freudian suppression, but in all habits which were learnt long ago and have now become automatic, such as writing and speaking. The emphasis upon consciousness has made a mystery of the “unconscious”, which ought to be in no way surprising. It does not much matter which of our two definitions of a “mind” we adopt. Let us, provisionally, adopt the first definition, so that a mind is all the mental events which form part of the history of a certain living body, or perhaps we should rather say a living brain. We can now tackle the question which is to decide whether we are emergent materialists or not, namely: Is a mind a structure of material units? I think it is clear that the answer to this question is in the negative. Even if a mind consists of all the events in a brain, it does not consist of bundles of these events grouped as physics groups them, i.e. it does not lump together all the events that make up one piece of matter in the brain, and then all the events that make up another, and so on. Mnemic causation is what concerns us most in studying mind, but this seems to demand a recourse to physics, if we assume, as seems plausible, that mental mnemic causation is due to effects upon the brain. This question, however, is still an open one. If mnemic causation is ultimate, mind is emergent. If not, the question is more difficult. As we saw earlier, there certainly is knowledge in psychology which cannot ever form part of physics. But as this point is important, I shall repeat the argument in different terms. The difference between physics and psychology is analogous to that between a postman’s knowledge of letters and the knowledge of a recipient of letters. The postman knows the movements of many letters, the recipient knows the contents of a few. We may regard the light and sound waves that go about the world as letters of which the physicist may know the destination; some few of them are addressed to human beings, and when read give psychological knowledge. Of course the analogy is not perfect, because the letters with which the physicist deals are continually changing during their journeys, as if they were written in fading ink, which, also, was not quite dry all the time, but occasionally got smudged with rain. However, the analogy may pass if not pressed. It would be possible without altering the detail of previous discussions, except that of Chapter XXV, to give a different turn to the argument, and make matter a structure composed of mental units. I am not quite sure that this is the wrong view. It arises not unnaturally from the argument as to data contained in Chapter XXV. We saw that all data are mental events in the narrowest and strictest sense, since they are percepts. Consequently all verification of causal laws consists in the occurrence of expected percepts. Consequently any inference beyond percepts (actual or possible) is incapable of being empirically tested. We shall therefore be prudent if we regard the non-mental events of physics as mere auxiliary concepts, not assumed to have any reality, but only introduced to simplify the laws of percepts. Thus matter will be a construction built out of percepts, and our metaphysic will be essentially that of Berkeley. If there are no non-mental events, causal laws will be very odd; for example, a hidden dictaphone may record a conversation although it did not exist at the time, since no one was perceiving it. But although this seems odd, it is not logically impossible. And it must be conceded that it enables us to interpret physics with a smaller amount of dubious inductive and analogical inference than is required if we admit non-mental events. In spite of the logical merits of this view, I cannot bring myself to accept it, though I am not sure that my reasons for disliking it are any better than Dr. Johnson’s. I find myself constitutionally incapable of believing that the sun would not exist on a day when he was everywhere hidden by clouds, or that the meat in a pie springs into existence at the moment when the pie is opened. I know the logical answer to such objections, and qua logician I think the answer a good one. The logical argument, however, does not even tend to show that there are not non-mental events; it only tends to show that we have no right to feel sure of their existence. For my part, I find myself in fact believing in them in spite of all that can be said to persuade me that I ought to feel doubtful. There is an argument, of a sort, against the view we are considering. I have been assuming that we admit the existence of other people and their perceptions, but question only the inference from perceptions to events of a different kind. Now there is no good reason why we should not carry our logical caution a step further. I cannot verify a theory by means of another man’s perceptions, but only by means of my own. Therefore the laws of physics can only be verified by me in so far as they lead to predictions of my percepts. If then, I refuse to admit non-mental events because they are not verifiable, I ought to refuse to admit mental events in every one except myself, on the same ground. Thus I am reduced to what is called “solipsism”, i.e. the theory that I alone exist. This is a view which is hard to refute, but still harder to believe. I once received a letter from a philosopher who professed to be a solipsist, but was surprised that there were no others! Yet this philosopher was by way of believing that no one else existed. This shows that solipsism is not really believed even by those who think they are convinced of its truth. We may go a step further. The past can only be verified indirectly, by means of its effects in the future; therefore the type of logical caution we have been considering should lead us to abstain from asserting that the past really occurred: we ought to regard it as consisting of auxiliary concepts convenient in stating the laws applicable to the future. And since the future, though verifiable if and when it occurs, is as yet unverified, we ought to suspend judgment about the future also. If we are not willing to go so far as this, there seems no reason to draw the line at the precise point where it was drawn by Berkeley. On these grounds I feel no shame in admitting the existence of non-mental events such as the laws of physics lead us to infer. Nevertheless, it is important to realise that other views are tenable.