Philosophy

by Bertrand Russell

We said a few pages ago that: Mental events are events in a region combining sensitivity and the law of learned reactions to a marked extent. For practical purposes, this means (subject to a proviso to be explained shortly) that a mental event is any event in a living brain. We explained that this does not mean that a mental event consists of matter in motion, which is what an old-fashioned physicist would regard as the sort of event that happens in a brain. Matter in motion, we have seen, is not an event in our sense, but a shorthand description of a very complicated causal process among events of a different sort. But we must say a few words in justification of our definition.

Let us consider some alternative definitions. A mental event, we might say, is one which is “experienced.” When is an event “experienced”? We might say: when it has “mnemic” effects, i.e. effects governed by the law of association. But we saw that this law applies to purely bodily events such as the contraction of the pupil, with which nothing “mental” seems to be connected. Thus if our definition is to serve, we shall have to define “experience” differently; we shall have to say that the mnemic effects must include something that can be called “knowledge.” This would suggest the definition: A mental event is anything that is remembered. But this is too narrow: we only remember a small proportion of our mental events. We might have regarded “consciousness” as the essence of mental events, but this view was examined and found inadequate in [Chapter XX]. Moreover, we do not want our definition to exclude the “unconscious”.

It is clear that the primary mental events, those about which there can be no question, are percepts. But percepts have certain peculiar causal properties, notably that they give rise to knowledge-reactions, and that they are capable of having mnemic effects which are cognitions. These causal properties, however, belong to some events which are not apparently percepts. It seems that any event in the brain may have these properties. And perhaps we were too hasty in saying that the contraction of the pupil on hearing a loud noise involves nothing “mental”. There may be other “mental” events connected with a human body besides those belonging to the central personality. I shall come back to this possibility presently. Meanwhile, I shall adhere to the above definition of a “mental” event, which, as we saw, makes mentality a matter of degree.

We can now return to the question: What is a mind? There may be mental events not forming part of the sort of group that we should call a “mind”, but there certainly are groups having that kind of unity that make us call them one mind. There are two marked characteristics of a mind: First, it is connected with a certain body; secondly, it has the unity of one “experience”. The two prima facie diverge in cases of dual or multiple personality, but I think this is more apparent than real. These two characteristics are, one physical, the other psychological. Let us consider each in turn as a possible definition of what we mean by one “mind”.

In the physical way, we begin by observing that every mental event known to us is also part of the history of a living body, and we define a “mind” as the group of mental events which form part of the history of a certain living body. The definition of a living body is chemical, and the reduction of chemistry to physics is clear in theory, though in practice the mathematics is too difficult. It is so 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: