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.
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.
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.
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.
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.
{{reflist|1|refs=
Uncharted Knowledge
Wisdom From Previous Realities
View as JSON for agents & LLMs