In their apologias, which have now become so common, men of science
never weary of pointing out that it is the method of science which
is really worthy of adoption by philosophers and that the results of
science are merely provisional. The philosopher who bases his system
upon the results reached at any given time by any given science has
ensured the ultimate downfall of his system. He is sometimes told that
the adoption of scientific methods, on the other hand, will enable him
to make sure progress. At first sight there seems to be a contradiction
here, for if the scientific method is infallible why are the results
reached by it provisional? To judge from the history of science, the
scientific method is excellent as a means of obtaining plausible
conclusions which are always wrong, but hardly as a means of reaching
the truth. The contradiction is only apparent, however, for it will
be found that there is a part of every discarded hypothesis which is
incorporated in the new theory. The discarded hypothesis proves to
have been too general; the scientific man made a mistake of the same
kind as the philosopher who uses the hypothesis as the basis of a
general system. It is now known, for instance, that Newton’s theory of
gravitation is very probably not exactly true; in most cases, however,
it remains very nearly true, and there are large regions of dynamical
astronomy which are unaffected by the alteration. The Newtonian laws
of motion, again, are not sufficient to describe the motion of bodies
moving with very large velocities, but they are very nearly true
for all ordinary velocities. That the theories which have taken the
place of those abandoned are exactly true is very improbable; they
are, however, nearer the truth. We may say, therefore, that while the
scientific method may, quite possibly, never enable us to reach the
exact truth, successive applications of it enable us to approximate
nearer and nearer to the exact truth. In this lies its chief difference
from the methods usually adopted in philosophy, which aim at obtaining,
at one blow, theories which shall never need revision. It is for this
reason that philosophy does not progress.
In what, then, does the scientific method consist? It would be
difficult to give a precise definition; it has, however, two main
characteristics, the choice of facts and the treatment of facts. It
does not seem to be generally recognised that scientific men do choose
their facts; there are many people who suppose that all facts are of
equal interest to scientific men, and that information respecting the
number of nightingales heard in Hertfordshire during a certain month,
for instance, is a contribution to scientific knowledge. It should
be obvious, however, that a mere random collection of facts is very
unlikely to aid either practice or theory. The aim of science is not to
form catalogues, but to form theories describing phenomena, and to this
end some facts are pertinent and a very great number are not. All men,
faced with a problem of any kind, choose such facts for examination
as they consider relevant. Sherlock Holmes often bewildered Watson by
pondering over facts that Watson considered irrelevant, but Watson’s
surprise was a proof that even he had a standard of relevance. The
history of any science shows that the facts first chosen were those
most likely to be repeated. Such facts obviously lead to statements
which have a greater or less degree of generality. That an unsupported
stone falls to the ground is a fact of this kind. The facts chosen
by the man of science are those that permit generalisation. For this
reason they usually differ entirely from the facts of interest to
historians. After selecting, in accordance with this principle, the
facts which are to be examined, the next step consists in establishing
relations between sets of these facts. The precise expression of these
relations is called a law of nature, to use a somewhat old-fashioned
terminology. If now all the relations between certain sets of facts
can be expressed in one general statement, that general statement is
called a scientific theory. The ultimate aim of the scientific method
is to create scientific theories. The scientific theory, however,
usually introduces an element which has not been or cannot be directly
observed, and also, as we have seen, usually proves to have been too
hasty a generalisation. Its function is to co-ordinate known phenomena
and to predict hitherto unobserved phenomena. The extent to which it
does this is the measure of its success as a scientific theory, and,
since the primary object of the scientific theory is to express the
harmonies which are found to exist in nature, we see at once that these
theories must have an æsthetic value. The measure of the success of a
scientific theory is, in fact, a measure of its æsthetic value, since
it is a measure of the extent to which it has introduced harmony in
what was before chaos.
It is in its æsthetic value that the justification of the scientific
theory is to be found, and with it the justification of the scientific
method. Since facts without laws would be of no interest, and laws
without theories would have, at most, a practical utility, we see that
the motives which guide the scientific man are, from the beginning,
manifestations of the æsthetic impulse. The reason why certain facts
and not others interest the scientific man, the reason why he makes a
choice, is because truth without beauty is as uninteresting to him as
to any other artist. In the words of Poincaré: “Le savant n’étudie pas
la nature parce que cela est utile; il l’étudie parce qu’il y prend
plaisir, et il y prend plaisir parce qu’elle est belle. Si la nature
n’était pas belle, elle ne vaudrait pas la peine d’être connue, la vie
ne vaudrait pas la peine d’être vécue.”