by     Reginald O. Kapp



THERE are, I have just shown, two diametrically opposed views of the nature of reality. To a set of questions to which the answers yes or no are the only possible alternatives, adherents of the one school would answer "yes" those of the other school "no". For want of better words I have called the two schools, respectively, monism and dualism. With the help of a definition of matter that is wide enough one can state the basic belief of the opposed schools correctly and fairly in a few simple words. Here are the two doctrines in plain antithesis:

According to monism both the behaviour and the structure of living bodies depend only on the unaided action of matter on matter. According to the opposed dualist school both the behaviour and the structure of living bodies depend partly on the action of matter on matter and partly also on the action of non-material influences on matter.

The immediate task is to find a definition of matter such that the above statements may be a fair presentation of the views of the two opposed schools.

The purpose of a definition is to ensure that the word defined shall be understood in the same sense by all concerned. This is a practical purpose. It means that a good definition should be a servant and not a master; it should help to clarify discussion, it should not dominate it. To serve this practical purpose a definition does not always need to be quite watertight. It may have to be in philosophy, where very rigorous standards are aimed at. But in science a small hole in a definition does not matter provided nothing unwanted is likely to slip through the hole. It is perfectly true that many working definitions used by scientists are such that anyone who exerted sufficient ingenuity could show that the definition included something that it was meant to exclude, or excluded something that it was meant to include. But so long as no one is going to be misled by the imperfections no misunderstanding can arise. Though it aims at accuracy, a definition that is to serve scientists must yet stop short of pedantry. Anyone who has served on a scientific nomenclature committee knows this full well. The members of such a committee soon learn that a definition gives better service if it is simple and clear, even if it has some tiny holes in it, than if, in the interest of pedantic accuracy, it has been made lengthy and obscure.

This has to be pointed out because I must not start on what I spoke of metaphorically in the last chapter as pillar shaking until I have made it clear to all who would assist in that destructive task what I shall mean when I use the word matter. And as I am only too well aware that many definitions of matter have been provided by philosophers, only to have the holes in them demonstrated by other philosophers, I must guard against attempts to divert attention from facts to definitions. I have often listened to some interesting discussion that was spoiled by the perverted ingenuity of those who like to deflect the course of a line of reasoning to an over-meticulous examination of the meaning of the terms used.

Be it remembered, therefore, that definitions are only needed when their absence might lead to a misunderstanding; that they need only be precise enough to serve this purpose; that their contribution to a line of reasoning is, at best, sterile; that definitions impose a strain on the understanding. Be it also remembered that definitions do not create problems; only facts do this. And be it lastly remembered that definitions do not solve problems or explain them away, though preoccupation with definitions may cause problems to be forgotten. If all this be remembered no harm will be done if I find a definition of matter that is no more watertight than those that have been proposed and rejected in the past. It need, in fact, be no more watertight than those definitions that are to be found in glossaries of technical terms.

One sometimes distinguishes between matter and energy or between matter and radiation. Then the word matter is understood to mean only ponderable substance. It is used in too narrow a sense for our present purpose. Those who support what in the last chapter I have called monism and say that the behaviour and structure of living bodies depend only on material circumstances, are not so naive as to mean that these things depend only on ponderable substance. When they say that mind and life are merely attributes of the material substance that forms the living body they mean attributes not only of ponderable substance but also of energy, of short wave radiation, of long wave radiation, of magnetic, electrostatic and gravitational fields, of electrons, protons, mesons and all other concepts that have a place in physical science. If the monistic school is to be fairly represented, then a definition of matter must include all these things.

To say that matter is everything observable by physical means might serve. But an ambiguity is introduced with the word observable. This word may be understood to apply only to direct observation or both to direct and indirect observation. If it is applied only to direct observation the suggested definition will prove too narrow; if it is applied both to direct and indirect observation the definition may prove too wide. To say that matter is everything observable by physical means would not often lead to misunderstanding; but it would do so sometimes. The holes in this definition are too large even for the reduced standard that will suffice for our practical purpose.

So let us consider the kind of observation that a physicist makes whenever he is observing something material. What characteristic is never absent from such an observation?

The physicist is using his organs of sense perception, aided very likely by scientific instruments. He is feeling something, or looking at something, or listening to something, or tasting or smelling something. Now one absolutely universal fact about an observation of this type is that the thing observed transmits a signal to the instrument of observation. I am using the word signal in its technical sense as used by physicists. When they speak of a signal they mean the cause of a change in the instrument used for the observation. The change may be of any kind; the instruments needed for its detection may be quite ordinary or very scientific and complicated.

That a thing cannot be observed if it does not send out a signal is obvious enough, too obvious to need elaboration. But it is the obviously true that best serves the purpose of a definition. So it might meet our present requirement to define matter as anything that can transmit a signal. I am confident that, for physicists, this definition would always include the same things and exclude the same things. But it might not do so for those who are less well acquainted with the nature of a signal. A layman might, mistakenly, think that some things were included that a physicist would know to be excluded. To give a very crude example, there are people who believe in ghosts. They say that the ghosts are non-material and they also say that these self-same ghosts make their presence known by signs that would be covered by the technical term "signal". Some further explanation is clearly needed if confusion is to be avoided.

Every observation requires that a change shall occur in the instrument of observation. If the instrument is the eye the change is chemical and is produced by the action of light on the retina; if the instrument is the ear the change consists in vibrations of very sensitive parts of the ear; if the instrument is the nose the change is again chemical; if the instrument is a galvanometer the change is in the flow of an electric current; if the instrument is a cloud chamber, and the thing observed an electron, the change consists in the condensation of some water vapour.

As every physicist knows, a change can only occur in a thing while energy is being transmitted to or from that thing. It is this transfer of energy that is called a signal if it occurs during an observation, and this is why no observation can be made unless a signal is received by the instrument of the observation.

The signal may take on a variety of forms. It may appear as the kinetic energy of a moving body, as when a thing is detected by its impact; it may appear as energy of radiation, as when a light or wireless signal is received; it may appear as thermal energy, as when a thing is detected by the heat that it emits or absorbs; it may appear as a change in a magnetic or any other field; .there is no limit to the variety of ways in which a transfer of energy can produce a change in an instrument of observation.

So to define matter as everything that can transmit a signal is to define it as everything that can transmit energy. I prefer this latter definition as it is less susceptible to misunderstanding among laymen; but it still needs a small correction. True, I do not think that it includes anything that ought, in logic and fairness, to be excluded.

But it does not, except possibly by implication, include energy itself. And energy must of course, be included in a definition of matter that is wide enough for our purpose. After all ponderable substance can be converted into energy and is thus converted during the synthesis of helium in the sun's deep interior. So a practical working definition might be to say that matter is energy and everything that can transmit energy.

Another definition amounts to the same thing. It can be reached by the following consideration. A thing that is transmitting energy must have location. If it did not the energy would, at the moment of transmission, disappear from space. And this, according to the principle of conservation of energy, it cannot do. When the signal necessary for the physical observation is received by the instrument of observation, that signal comes from somewhere. To say that matter is energy and everything that can transmit energy is, therefore, to exclude from the definition everything that lacks location.

It is also to include everything that possesses location. For if one imagines a thing that cannot transmit energy, that thing cannot send a signal from anywhere. There is no means of saying that it has such and such a location. It might be anywhere or nowhere. And for such a thing, it is meaningless to say that it has any location at all. So a second definition that includes just what ought to be included and excludes just what ought to be excluded, is to say that matter is everything with location.

Perhaps I ought to say a word to those who would like, with the help of the quantum theory, to find a hole in the definition. I am well aware that the location of an electron cannot always be known with absolute precision. But that does not mean that the electron does not have location. To define matter as everything of which the location is completely knowable would be wrong, but to define it as everything that has location does not leave a hole large enough to let in any ambiguity. I am sure that adherents of all monistic schools believe that anything with location may help to determine the behaviour and structure of living bodies and that nothing without location could conceivably do so. They would be fairly represented as saying that the behaviour and structure of living things depend only on the action on each other of things with location.

As a definition of matter I prefer "everything that has location" to "energy and everything that can transmit energy". It is shorter, simpler, and less liable to be misunderstood. And it has the further paradoxical advantage of unattractiveness. By this I mean that it is easy with the help of this definition to demonstrate the insecurity, be it real or only apparent, of the pillars that support the dualistic roof. One cannot do so as clearly and as cogently when one uses any definition that presents the fundamental characteristics of matter in less stark and uncompromising terms. Those who like to see the roof of their dualistic home on firm supports will not like to have to speak of the non-material influences in which they believe as lacking location, as literally nowhere. The choice between material and somewhere on the one hand and non-material and nowhere on the other will, for many, not be an attractive one. But in science, it cannot be repeated too often, it is the criterion of truth and not the criterion of attractiveness by which conclusions must be judged.

So from now onwards I shall apply the term monist to all those who believe that the whole of reality has location and I shall apply the term dualist to all those who believe that a part of reality, of active reality capable of influencing the course of material events, lacks location.

I admit that to use the words monist and dualist thus is a little arbitrary. I fear that some who deny emphatically that anything without location can exist would yet not like to be called monists if only because monism is but another word for materialism. I can only apologise to these and assure them that no moral opprobrium attaches to the label monist as intended here. It is my task to develop a difficult theme as clearly and simply as possible. I need single words by which to distinguish between two opposed views of the nature of reality and these two describe those opposed views more accurately than any others that I can find.

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