Philosophy

the leaf is, but is an event occupying a certain volume in our brains during the time that we see the leaf. Seeing the leaf consists of the existence, in the region occupied by our brain, of a green patch causally connected with the leaf, or rather with a series of events emanating from the place in physical space where physics places the leaf. The percept is one of this series of events, differing from the others in its effects owing to the peculiarities of the region in which it occurs—or perhaps it would be more correct to say that the different effects are the peculiarities of the region. Thus “mind” and “mental” are merely approximate concepts, giving a convenient shorthand for certain approximate laws. In a completed science, the word “mind” and the word “matter” would both disappear, and would be replaced by causal laws concerning “events”, the only events known to us otherwise than in their mathematical and causal properties being percepts, which are events situated in the same region as a brain and having effects of a peculiar sort called “knowledge-reactions”. It will be seen that the view which I am advocating is neither materialism nor mentalism, but what we call “neutral monism”. It is monism in the sense that it regards the world as composed of only one kind of stuff, namely events; but it is pluralism in the sense that it admits the existence of a great multiplicity of events, each minimal event being a logically self-subsistent entity. There is, however, another question, not quite the same as this, namely the question as to the relations of psychology and physics. If we knew more, would psychology be absorbed in physics? or, conversely, would physics be absorbed in psychology? A man may be a materialist and yet hold that psychology is an independent science; this is the view taken by Dr. Broad in his important book on The Mind and its Place in Nature. He holds that a mind is a material structure, but that it has properties which could not, even theoretically, be inferred from those of its material constituents. He points out that structures very often have properties which, in the present state of our knowledge, cannot be inferred from the properties and relations of their parts. Water has many properties which we cannot infer from those of hydrogen and oxygen, even if we suppose ourselves to know the structure of the molecule of water more completely than we do as yet. Properties of a whole which cannot, even theoretically, be inferred from the properties and relations of its parts are called by Dr. Broad “emergent” properties. Thus he holds that a mind (or brain) has properties which are “emergent”, and to this extent psychology will be independent of physics and chemistry. The “emergent” properties of minds will only be discoverable by observation of minds, not by inference from the laws of physics and chemistry. This possibility is an important one, and it will be worth while to consider it. Our decision to regard a unit of matter as itself not ultimate, but an assemblage of events, somewhat alters the form of our question as to “emergent” properties. We have to ask: Is matter emergent from events? Is mind emergent from events? If the former, is mind emergent from matter, or deducible from the properties of matter, or neither? If the latter, is matter emergent from mind or deducible from the properties of mind, or neither? Of course, if neither mind nor matter is emergent from events, these latter questions do not arise. Let us coin a word, “chrono-geography”, for the science which begins with events having space-time relations and does not assume at the outset that certain strings of them can be treated as persistent material units or as minds. Then we have to ask ourselves first: can the science of matter, as it appears in physics and chemistry, be wholly reduced to chrono-geography? If no, matter is emergent from events; if yes, it is not emergent. Is matter emergent from events? In the present state of science it is difficult to give a decided answer to this question. The notion of matter, in modern physics, has become absorbed into the notion of energy. Eddington, in his Mathematical Theory of Relativity shows that, in virtue of the laws assumed concerning events, there must be something having the observed properties of matter and energy as regards conservation. This he calls the “material-energy-tensor”, and suggests that it is the reality which we sometimes call “matter” and sometimes “energy”. To this extent, matter has been shown to be not emergent. But the existence of electrons and protons (to the extent that they do exist) has not yet been deduced from the general theory of relativity, though attempts are being made and may at any moment succeed. If and when these attempts succeed, physics will cease to be in any degree independent of chrono-geography, but for the present it remains in part independent. As for chemistry, although we cannot practically reduce it all to physics, we can see how, theoretically, this could be done, and I think it is safe to assume that it is not an ultimately independent science. The question we have been asking is: could we predict, theoretically, from the laws of events that there must be material units obeying the laws which they do in fact obey, or is this a new, logically independent, fact? In theory we might be able to prove that it is not independent, but it would be very difficult to prove that it is. The present position is, broadly speaking, that the continuous properties of the physical world can be deduced from chrono-geography, but not the discontinuous facts, viz. electrons and protons and Planck’s quantum. Thus for the present materiality is practically, though perhaps not theoretically, an emergent characteristic of certain groups of events. Is mind emergent from events? This question, as yet, can hardly be even discussed intelligently, because psychology is not a sufficiently advanced science. There are, nevertheless, some points to be noted. Chrono-geography is concerned only with the abstract mathematical properties of events, and cannot conceivably, unless it is radically transformed, prove that there are visual events, or auditory events, or events of any of the kinds that we know by perception. In this sense, psychology is certainly emergent from chrono-geography and also from physics, and it is hard to see how it can ever cease to be so. The reason for this is that our knowledge of data contains features of a qualitative sort, which cannot be deduced from the merely mathematical features of the space-time events inferred from data, and yet these abstract mathematical features are all that we can legitimately infer. The above argument decides also that mind must be emergent from matter, if it is a material structure. No amount of physics can ever tell us all that we do in fact know about our own percepts. We have still to ask whether we are to regard a mind as a structure of material units or not. If we do so regard it, we are, so far as mind is concerned, emergent materialists in view of what we have just decided; this is the view favoured by Dr. Broad. If we do not so regard it, we are in no sense materialists. In favour of the materialist view, there is the fact that, so far as our experience goes, minds only emerge in connection with certain physical structures, namely living bodies, and that mental development increases with a certain kind of complexity of physical structure. We cannot set against this the argument that minds have peculiar characteristics, for this is quite consistent with emergent materialism. If we are to refute it, it must be by finding out what sort of group of events constitutes a mind. It is time to address ourselves to this question. What is a mind? It is obvious, to begin with, that a mind must be a group of mental events, since we have rejected the view that it is a single simple entity such as the ego was formerly supposed to be. Our first step, therefore, is to be clear as to what we mean by a “mental” event. 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