Lecture V - Psychological and Physical Causal Laws

Lecture V - Psychological and Physical Causal Laws [Bertrand Russell's essay/lecture: The Analysis of Mind]

The traditional conception of cause and effect is one which

modern science shows to be fundamentally erroneous, and requiring

to be replaced by a quite different notion, that of LAWS OF

CHANGE. In the traditional conception, a particular event A

caused a particular event B, and by this it was implied that,

given any event B, some earlier event A could be discovered which

had a relation to it, such that--

(1) Whenever A occurred, it was followed by B;

(2) In this sequence, there was something "necessary," not a mere

de facto occurrence of A first and then B.

The second point is illustrated by the old discussion as to

whether it can be said that day causes night, on the ground that

day is always followed by night. The orthodox answer was that day

could not be called the cause of night, because it would not be

followed by night if the earth's rotation were to cease, or

rather to grow so slow that one complete rotation would take a

year. A cause, it was held, must be such that under no

conceivable circumstances could it fail to be followed by its

effect.

As a matter of fact, such sequences as were sought by believers

in the traditional form of causation have not so far been found

in nature. Everything in nature is apparently in a state of

continuous change,* so that what we call one "event" turns out to

be really a process. If this event is to cause another event, the

two will have to be contiguous in time; for if there is any

interval between them, something may happen during that interval

to prevent the expected effect. Cause and effect, therefore, will

have to be temporally contiguous processes. It is difficult to

believe, at any rate where physical laws are concerned, that the

earlier part of the process which is the cause can make any

difference to the effect, so long as the later part of the

process which is the cause remains unchanged. Suppose, for

example, that a man dies of arsenic poisoning, we say that his

taking arsenic was the cause of death. But clearly the process by

which he acquired the arsenic is irrelevant: everything that

happened before he swallowed it may be ignored, since it cannot

alter the effect except in so far as it alters his condition at

the moment of taking the dose. But we may go further: swallowing

arsenic is not really the proximate cause of death, since a man

might be shot through the head immediately after taking the dose,

and then it would not be of arsenic that he would die. The

arsenic produces certain physiological changes, which take a

finite time before they end in death. The earlier parts of these

changes can be ruled out in the same way as we can rule out the

process by which the arsenic was acquired. Proceeding in this

way, we can shorten the process which we are calling the cause

more and more. Similarly we shall have to shorten the effect. It

may happen that immediately after the man's death his body is

blown to pieces by a bomb. We cannot say what will happen after

the man's death, through merely knowing that he has died as the

result of arsenic poisoning. Thus, if we are to take the cause as

one event and the effect as another, both must be shortened

indefinitely. The result is that we merely have, as the

embodiment of our causal law, a certain direction of change at

each moment. Hence we are brought to differential equations as

embodying causal laws. A physical law does not say "A will be

followed by B," but tells us what acceleration a particle will

have under given circumstances, i.e. it tells us how the

particle's motion is changing at each moment, not where the

particle will be at some future moment.

* The theory of quanta suggests that the continuity is only

apparent. If so, we shall be able theoretically to reach events

which are not processes. But in what is directly observable there

is still apparent continuity, which justifies the above remarks

for the prevent.

Laws embodied in differential equations may possibly be exact,

but cannot be known to be so. All that we can know empirically is

approximate and liable to exceptions; the exact laws that are

assumed in physics are known to be somewhere near the truth, but

are not known to be true just as they stand. The laws that we

actually know empirically have the form of the traditional causal

laws, except that they are not to be regarded as universal or

necessary. "Taking arsenic is followed by death" is a good

empirical generalization; it may have exceptions, but they will

be rare. As against the professedly exact laws of physics, such

empirical generalizations have the advantage that they deal with

observable phenomena. We cannot observe infinitesimals, whether

in time or space; we do not even know whether time and space are

infinitely divisible. Therefore rough empirical generalizations

have a definite place in science, in spite of not being exact of

universal. They are the data for more exact laws, and the grounds

for believing that they are USUALLY true are stronger than the

grounds for believing that the more exact laws are ALWAYS true.

Science starts, therefore, from generalizations of the form, "A

is usually followed by B." This is the nearest approach that can

be made to a causal law of the traditional sort. It may happen in

any particular instance that A is ALWAYS followed by B, but we

cannot know this, since we cannot foresee all the perfectly

possible circumstances that might make the sequence fail, or know

that none of them will actually occur. If, however, we know of a

very large number of cases in which A is followed by B, and few

or none in which the sequence fails, we shall in PRACTICE be

justified in saying "A causes B," provided we do not attach to

the notion of cause any of the metaphysical superstitions that

have gathered about the word.

There is another point, besides lack of universality and

necessity, which it is important to realize as regards causes in

the above sense, and that is the lack of uniqueness. It is

generally assumed that, given any event, there is some one

phenomenon which is THE cause of the event in question. This

seems to be a mere mistake. Cause, in the only sense in which it

can be practically applied, means "nearly invariable antecedent."

We cannot in practice obtain an antecedent which is QUITE

invariable, for this would require us to take account of the

whole universe, since something not taken account of may prevent

the expected effect. We cannot distinguish, among nearly

invariable antecedents, one as THE cause, and the others as

merely its concomitants: the attempt to do this depends upon a

notion of cause which is derived from will, and will (as we shall

see later) is not at all the sort of thing that it is generally

supposed to be, nor is there any reason to think that in the

physical world there is anything even remotely analogous to what

will is supposed to be. If we could find one antecedent, and only

one, that was QUITE invariable, we could call that one THE cause

without introducing any notion derived from mistaken ideas about

will. But in fact we cannot find any antecedent that we know to

be quite invariable, and we can find many that are nearly so. For

example, men leave a factory for dinner when the hooter sounds at

twelve o'clock. You may say the hooter is THE cause of their

leaving. But innumerable other hooters in other factories, which

also always sound at twelve o'clock, have just as good a right to

be called the cause. Thus every event has many nearly invariable

antecedents, and therefore many antecedents which may be called

its cause.

The laws of traditional physics, in the form in which they deal

with movements of matter or electricity, have an apparent

simplicity which somewhat conceals the empirical character of

what they assert. A piece of matter, as it is known empirically,

is not a single existing thing, but a system of existing things.

When several people simultaneously see the same table, they all

see something different; therefore "the" table, which they are

supposed all to see, must be either a hypothesis or a

construction. "The" table is to be neutral as between different

observers: it does not favour the aspect seen by one man at the

expense of that seen by another. It was natural, though to my

mind mistaken, to regard the "real" table as the common cause of

all the appearances which the table presents (as we say) to

different observers. But why should we suppose that there is some

one common cause of all these appearances? As we have just seen,

the notion of "cause" is not so reliable as to allow us to infer

the existence of something that, by its very nature, can never be

observed.

Instead of looking for an impartial source, we can secure

neutrality by the equal representation of all parties. Instead of

supposing that there is some unknown cause, the "real" table,

behind the different sensations of those who are said to be

looking at the table, we may take the whole set of these

sensations (together possibly with certain other particulars) as

actually BEING the table. That is to say, the table which is

neutral as between different observers (actual and possible) is

the set of all those particulars which would naturally be called

"aspects" of the table from different points of view. (This is a

first approximation, modified later.)

It may be said: If there is no single existent which is the

source of all these "aspects," how are they collected together?

The answer is simple: Just as they would be if there were such a

single existent. The supposed "real" table underlying its

appearances is, in any case, not itself perceived, but inferred,

and the question whether such-and-such a particular is an

"aspect" of this table is only to be settled by the connection of

the particular in question with the one or more particulars by

which the table is defined. That is to say, even if we assume a

"real" table, the particulars which are its aspects have to be

collected together by their relations to each other, not to it,

since it is merely inferred from them. We have only, therefore,

to notice how they are collected together, and we can then keep

the collection without assuming any "real" table as distinct from

the collection. When different people see what they call the same

table, they see things which are not exactly the same, owing to

difference of point of view, but which are sufficiently alike to

be described in the same words, so long as no great accuracy or

minuteness is sought. These closely similar particulars are

collected together by their similarity primarily and, more

correctly, by the fact that they are related to each other

approximately according to the laws of perspective and of

reflection and diffraction of light. I suggest, as a first

approximation, that these particulars, together with such

correlated others as are unperceived, jointly ARE the table; and

that a similar definition applies to all physical objects.*

*See "Our Knowledge of the External World" (Allen & Unwin),

chaps. iii and iv.

In order to eliminate the reference to our perceptions, which

introduces an irrelevant psychological suggestion, I will take a

different illustration, namely, stellar photography. A

photographic plate exposed on a clear night reproduces the

appearance of the portion of the sky concerned, with more or

fewer stars according to the power of the telescope that is being

used. Each separate star which is photographed produces its

separate effect on the plate, just as it would upon ourselves if

we were looking at the sky. If we assume, as science normally

does, the continuity of physical processes, we are forced to

conclude that, at the place where the plate is, and at all places

between it and a star which it photographs, SOMETHING is

happening which is specially connected with that star. In the

days when the aether was less in doubt, we should have said that

what was happening was a certain kind of transverse vibration in

the aether. But it is not necessary or desirable to be so

explicit: all that we need say is that SOMETHING happens which is

specially connected with the star in question. It must be

something specially connected with that star, since that star

produces its own special effect upon the plate. Whatever it is

must be the end of a process which starts from the star and

radiates outwards, partly on general grounds of continuity,

partly to account for the fact that light is transmitted with a

certain definite velocity. We thus arrive at the conclusion that,

if a certain star is visible at a certain place, or could be

photographed by a sufficiently sensitive plate at that place,

something is happening there which is specially connected with

that star. Therefore in every place at all times a vast multitude

of things must be happening, namely, at least one for every

physical object which can be seen or photographed from that

place. We can classify such happenings on either of two

principles:

(1) We can collect together all the happenings in one place, as

is done by photography so far as light is concerned;

(2) We can collect together all the happenings, in different

places, which are connected in the way that common sense regards

as being due to their emanating from one object.

Thus, to return to the stars, we can collect together either--

(1) All the appearances of different stars in a given place, or,

(2) All the appearances of a given star in different places.

But when I speak of "appearances," I do so only for brevity: I do

not mean anything that must "appear" to somebody, but only that

happening, whatever it may be, which is connected, at the place

in question, with a given physical object--according to the old

orthodox theory, it would be a transverse vibration in the

aether. Like the different appearances of the table to a number

of simultaneous observers, the different particulars that belong

to one physical object are to be collected together by continuity

and inherent laws of correlation, not by their supposed causal

connection with an unknown assumed existent called a piece of

matter, which would be a mere unnecessary metaphysical thing in

itself. A piece of matter, according to the definition that I

propose, is, as a first approximation,* the collection of all

those correlated particulars which would normally be regarded as

its appearances or effects in different places. Some further

elaborations are desirable, but we can ignore them for the

present. I shall return to them at the end of this lecture.

*The exact definition of a piece of matter as a construction will

be given later.

According to the view that I am suggesting, a physical object or

piece of matter is the collection of all those correlated

particulars which would be regarded by common sense as its

effects or appearances in different places. On the other hand,

all the happenings in a given place represent what common sense

would regard as the appearances of a number of different objects

as viewed from that place. All the happenings in one place may be

regarded as the view of the world from that place. I shall call

the view of the world from a given place a "perspective." A

photograph represents a perspective. On the other hand, if

photographs of the stars were taken in all points throughout

space, and in all such photographs a certain star, say Sirius,

were picked out whenever it appeared, all the different

appearances of Sirius, taken together, would represent Sirius.

For the understanding of the difference between psychology and

physics it is vital to understand these two ways of classifying

particulars, namely:

(1) According to the place where they occur;

(2) According to the system of correlated particulars in

different places to which they belong, such system being defined

as a physical object.

Given a system of particulars which is a physical object, I shall

define that one of the system which is in a given place (if any)

as the "appearance of that object in that place."

When the appearance of an object in a given place changes, it is

found that one or other of two things occurs. The two

possibilities may be illustrated by an example. You are in a room

with a man, whom you see: you may cease to see him either by

shutting your eyes or by his going out of the room. In the first

case, his appearance to other people remains unchanged; in the

second, his appearance changes from all places. In the first

case, you say that it is not he who has changed, but your eyes;

in the second, you say that he has changed. Generalizing, we

distinguish--

(1) Cases in which only certain appearances of the object change,

while others, and especially appearances from places very near to

the object, do not change;

(2) Cases where all, or almost all, the appearances of the object

undergo a connected change.

In the first case, the change is attributed to the medium between

the object and the place; in the second, it is attributed to the

object itself.*

* The application of this distinction to motion raises

complications due to relativity, but we may ignore these for our

present purposes.

It is the frequency of the latter kind of change, and the

comparatively simple nature of the laws governing the

simultaneous alterations of appearances in such cases, that have

made it possible to treat a physical object as one thing, and to

overlook the fact that it is a system of particulars. When a

number of people at a theatre watch an actor, the changes in

their several perspectives are so similar and so closely

correlated that all are popularly regarded as identical with each

other and with the changes of the actor himself. So long as all

the changes in the appearances of a body are thus correlated

there is no pressing prima facie need to break up the system of

appearances, or to realize that the body in question is not

really one thing but a set of correlated particulars. It is

especially and primarily such changes that physics deals with,

i.e. it deals primarily with processes in which the unity of a

physical object need not be broken up because all its appearances

change simultaneously according to the same law--or, if not all,

at any rate all from places sufficiently near to the object, with

in creasing accuracy as we approach the object.

The changes in appearances of an object which are due to changes

in the intervening medium will not affect, or will affect only

very slightly, the appearances from places close to the object.

If the appearances from sufficiently neighbouring places are

either wholly un changed, or changed to a diminishing extent

which has zero for its limit, it is usually found that the

changes can be accounted for by changes in objects which are

between the object in question and the places from which its

appearance has changed appreciably. Thus physics is able to

reduce the laws of most changes with which it deals to changes in

physical objects, and to state most of its fundamental laws in

terms of matter. It is only in those cases in which the unity of

the system of appearances constituting a piece of matter has to

be broken up, that the statement of what is happening cannot be

made exclusively in terms of matter. The whole of psychology, we

shall find, is included among such cases; hence their importance

for our purposes.

We can now begin to understand one of the fundamental differences

between physics and psychology. Physics treats as a unit the

whole system of appearances of a piece of matter, whereas

psychology is interested in certain of these appearances

themselves. Confining ourselves for the moment to the psychology

of perceptions, we observe that perceptions are certain of the

appearances of physical objects. From the point of view that we

have been hitherto adopting, we might define them as the

appearances of objects at places from which sense-organs and the

suitable parts of the nervous system form part of the intervening

medium. Just as a photographic plate receives a different

impression of a cluster of stars when a telescope is part of the

intervening medium, so a brain receives a different impression

when an eye and an optic nerve are part of the intervening

medium. An impression due to this sort of intervening medium is

called a perception, and is interesting to psychology on its own

account, not merely as one of the set of correlated particulars

which is the physical object of which (as we say) we are having a

perception.

We spoke earlier of two ways of classifying particulars. One way

collects together the appearances commonly regarded as a given

object from different places; this is, broadly speaking, the way

of physics, leading to the construction of physical objects as

sets of such appearances. The other way collects together the

appearances of different objects from a given place, the result

being what we call a perspective. In the particular case where

the place concerned is a human brain, the perspective belonging

to the place consists of all the perceptions of a certain man at

a given time. Thus classification by perspectives is relevant to

psychology, and is essential in defining what we mean by one

mind.

I do not wish to suggest that the way in which I have been

defining perceptions is the only possible way, or even the best

way. It is the way that arose naturally out of our present topic.

But when we approach psychology from a more introspective

standpoint, we have to distinguish sensations and perceptions, if

possible, from other mental occurrences, if any. We have also to

consider the psychological effects of sensations, as opposed to

their physical causes and correlates. These problems are quite

distinct from those with which we have been concerned in the

present lecture, and I shall not deal with them until a later

stage.

It is clear that psychology is concerned essentially with actual

particulars, not merely with systems of particulars. In this it

differs from physics, which, broadly speaking, is concerned with

the cases in which all the particulars which make up one physical

object can be treated as a single causal unit, or rather the

particulars which are sufficiently near to the object of which

they are appearances can be so treated. The laws which physics

seeks can, broadly speaking, be stated by treating such systems

of particulars as causal units. The laws which psychology seeks

cannot be so stated, since the particulars themselves are what

interests the psychologist. This is one of the fundamental

differences between physics and psychology; and to make it clear

has been the main purpose of this lecture.

I will conclude with an attempt to give a more precise definition

of a piece of matter. The appearances of a piece of matter from

different places change partly according to intrinsic laws (the

laws of perspective, in the case of visual shape), partly

according to the nature of the intervening medium--fog, blue

spectacles, telescopes, microscopes, sense-organs, etc. As we

approach nearer to the object, the effect of the intervening

medium grows less. In a generalized sense, all the intrinsic laws

of change of appearance may be called "laws of perspective."

Given any appearance of an object, we can construct

hypothetically a certain system of appearances to which the

appearance in question would belong if the laws of perspective

alone were concerned. If we construct this hypothetical system

for each appearance of the object in turn, the system

corresponding to a given appearance x will be independent of any

distortion due to the medium beyond x, and will only embody such

distortion as is due to the medium between x and the object.

Thus, as the appearance by which our hypothetical system is

defined is moved nearer and nearer to the object, the

hypothetical system of appearances defined by its means embodies

less and less of the effect of the medium. The different sets of

appearances resulting from moving x nearer and nearer to the

object will approach to a limiting set, and this limiting set

will be that system of appearances which the object would present

if the laws of perspective alone were operative and the medium

exercised no distorting effect. This limiting set of appearances

may be defined, for purposes of physics, as the piece of matter

concerned.

___

End of Lecture V - Psychological and Physical Causal Laws [Bertrand Russell's essay/lecture: The Analysis of Mind]

Read next: Lecture VI- Introspection

Read previous: Lecture IV - Influence of Past History on Present Occurrences in Living Organisms

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