The Analysis of Mind, Bertrand Russell [best desktop ebook reader .txt] 📗

mnemic phenomena, without admixture

of anything hypothetical.

 

Whenever the effect resulting from a stimulus to an organism

differs according to the past history of the organism, without

our being able actually to detect any relevant difference in its

present structure, we will speak of “mnemic causation,” provided

we can discover laws embodying the influence of the past. In

ordinary physical causation, as it appears to common sense, we

have approximate uniformities of sequence, such as “lightning is

followed by thunder,” “drunkenness is followed by headache,” and

so on. None of these sequences are theoretically invariable,

since something may intervene to disturb them. In order to obtain

invariable physical laws, we have to proceed to differential

equations, showing the direction of change at each moment, not

the integral change after a finite interval, however short. But

for the purposes of daily life many sequences are to all in tents

and purposes invariable. With the behaviour of human beings,

however, this is by no means the case. If you say to an

Englishman, “You have a smut on your nose,” he will proceed to

remove it, but there will be no such effect if you say the same

thing to a Frenchman who knows no English. The effect of words

upon the hearer is a mnemic phenomena, since it depends upon the

past experience which gave him understanding of the words. If

there are to be purely psychological causal laws, taking no

account of the brain and the rest of the body, they will have to

be of the form, not “X now causes Y now,” but—

 

“A, B, C, … in the past, together with X now, cause Y now.”

For it cannot be successfully maintained that our understanding

of a word, for example, is an actual existent content of the mind

at times when we are not thinking of the word. It is merely what

may be called a “disposition,” i.e. it is capable of being

aroused whenever we hear the word or happen to think of it. A

“disposition” is not something actual, but merely the mnemic

portion of a mnemic causal law.

 

In such a law as “A, B, C, … in the past, together with X

now, cause Y now,” we will call A, B, C, … the mnemic cause,

X the occasion or stimulus, and Y the reaction. All cases in

which experience influences behaviour are instances of mnemic

causation.

 

Believers in psychophysical parallelism hold that psychology can

theoretically be freed entirely from all dependence on physiology

or physics. That is to say, they believe that every psychical

event has a psychical cause and a physical concomitant. If there

is to be parallelism, it is easy to prove by mathematical logic

that the causation in physical and psychical matters must be of

the same sort, and it is impossible that mnemic causation should

exist in psychology but not in physics. But if psychology is to

be independent of physiology, and if physiology can be reduced to

physics, it would seem that mnemic causation is essential in

psychology. Otherwise we shall be compelled to believe that all

our knowledge, all our store of images and memories, all our

mental habits, are at all times existing in some latent mental

form, and are not merely aroused by the stimuli which lead to

their display. This is a very difficult hypothesis. It seems to

me that if, as a matter of method rather than metaphysics, we

desire to obtain as much independence for psychology as is

practically feasible, we shall do better to accept mnemic

causation in psychology protem, and therefore reject parallelism,

since there is no good ground for admitting mnemic causation in

physics.

 

It is perhaps worth while to observe that mnemic causation is

what led Bergson to deny that there is causation. at all in the

psychical sphere. He points out, very truly, that the same

stimulus, repeated, does not have the same consequences, and he

argues that this is contrary to the maxim, “same cause, same

effect.” It is only necessary, however, to take account of past

occurrences and include them with the cause, in order to

re-establish the maxim, and the possibility of psychological

causal laws. The metaphysical conception of a cause lingers in

our manner of viewing causal laws: we want to be able to FEEL a

connection between cause and effect, and to be able to imagine

the cause as “operating.” This makes us unwilling to regard

causal laws as MERELY observed uniformities of sequence; yet that

is all that science has to offer. To ask why such-and-such a kind

of sequence occurs is either to ask a meaningless question, or to

demand some more general kind of sequence which includes the one

in question. The widest empirical laws of sequence known at any

time can only be “explained” in the sense of being subsumed by

later discoveries under wider laws; but these wider laws, until

they in turn are subsumed, will remain brute facts, resting

solely upon observation, not upon some supposed inherent

rationality.

 

There is therefore no a priori objection to a causal law in which

part of the cause has ceased to exist. To argue against such a

law on the ground that what is past cannot operate now, is to

introduce the old metaphysical notion of cause, for which science

can find no place. The only reason that could be validly alleged

against mnemic causation would be that, in fact, all the

phenomena can be explained without it. They are explained without

it by Semon’s “engram,” or by any theory which regards the

results of experience as embodied in modifications of the brain

and nerves. But they are not explained, unless with extreme

artificiality, by any theory which regards the latent effects of

experience as psychical rather than physical. Those who desire to

make psychology as far as possible independent of physiology

would do well, it seems to me, if they adopted mnemic causation.

For my part, however, I have no such desire, and I shall

therefore endeavour to state the grounds which occur to me in

favour of some such view as that of the “engram.”

 

One of the first points to be urged is that mnemic phenomena are

just as much to be found in physiology as in psychology. They are

even to be found in plants, as Sir Francis Darwin pointed out

(cf. Semon, “Die Mneme,” 2nd edition, p. 28 n.). Habit is a

characteristic of the body at least as much as of the mind. We

should, therefore, be compelled to allow the intrusion of mnemic

causation, if admitted at all, into non-psychological regions,

which ought, one feels, to be subject only to causation of the

ordinary physical sort. The fact is that a great deal of what, at

first sight, distinguishes psychology from physics is found, on

examination, to be common to psychology and physiology; this

whole question of the influence of experience is a case in point.

Now it is possible, of course, to take the view advocated by

Professor J. S. Haldane, who contends that physiology is not

theoretically reducible to physics and chemistry.* But the weight

of opinion among physiologists appears to be against him on this

point; and we ought certainly to require very strong evidence

before admitting any such breach of continuity as between living

and dead matter. The argument from the existence of mnemic

phenomena in physiology must therefore be allowed a certain

weight against the hypothesis that mnemic causation is ultimate.

 

* See his “The New Physiology and Other Addresses,” Griffin,

1919, also the symposium, “Are Physical, Biological and

Psychological Categories Irreducible?” in “Life and Finite

Individuality,” edited for the Aristotelian Society, with an

Introduction. By H. Wildon Carr, Williams & Norgate, 1918.

 

The argument from the connection of brain-lesions with loss of

memory is not so strong as it looks, though it has also, some

weight. What we know is that memory, and mnemic phenomena

generally, can be disturbed or destroyed by changes in the brain.

This certainly proves that the brain plays an essential part in

the causation of memory, but does not prove that a certain state

of the brain is, by itself, a sufficient condition for the

existence of memory. Yet it is this last that has to be proved.

The theory of the engram, or any similar theory, has to maintain

that, given a body and brain in a suitable state, a man will have

a certain memory, without the need of any further conditions.

What is known, however, is only that he will not have memories if

his body and brain are not in a suitable state. That is to say,

the appropriate state of body and brain is proved to be necessary

for memory, but not to be sufficient. So far, therefore, as our

definite knowledge goes, memory may require for its causation a

past occurrence as well as a certain present state of the brain.

 

In order to prove conclusively that mnemic phenomena arise

whenever certain physiological conditions are fulfilled, we ought

to be able actually to see differences between the brain of a man

who speaks English and that of a man who speaks French, between

the brain of a man who has seen New York and can recall it, and

that of a man who has never seen that city. It may be that the

time will come when this will be possible, but at present we are

very far removed from it. At present, there is, so far as I am

aware, no good evidence that every difference between the

knowledge possessed by A and that possessed by B is paralleled by

some difference in their brains. We may believe that this is the

case, but if we do, our belief is based upon analogies and

general scientific maxims, not upon any foundation of detailed

observation. I am myself inclined, as a working hypothesis, to

adopt the belief in question, and to hold that past experience

only affects present behaviour through modifications of

physiological structure. But the evidence seems not quite

conclusive, so that I do not think we ought to forget the other

hypothesis, or to reject entirely the possibility that mnemic

causation may be the ultimate explanation of mnemic phenomena. I

say this, not because I think it LIKELY that mnemic causation is

ultimate, but merely because I think it POSSIBLE, and because it

often turns out important to the progress of science to remember

hypotheses which have previously seemed improbable.

 

LECTURE V. PSYCHOLOGICAL AND PHYSICAL CAUSAL LAWS

 

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