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