Philosophy

by Bertrand Russell

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.