Among philosophical problems the problem of knowledge has in the last
century occupied a foremost place. It is natural, then, to ask how
Darwin and the hypothesis whose most eminent representative he is, stand
to this problem.
Darwin started an hypothesis. But every hypothesis is won by inference
from certain presuppositions, and every inference is based on
the general principles of human thought. The evolution hypothesis
presupposes, then, human thought and its principles. And not only
the abstract logical principles are thus presupposed. The evolution
hypothesis purports to be not only a formal arrangement of phenomena,
but to express also the law of a real process. It supposes, then,
that the real data--all that in our knowledge which we do not produce
ourselves, but which we in the main simply receive--are subjected
to laws which are at least analogous to the logical relations of our
thoughts; in other words, it assumes the validity of the principle of
causality. If organic species could arise without cause there would
be no use in framing hypotheses. Only if we assume the principle of
causality, is there a problem to solve.
Though Darwinism has had a great influence on philosophy considered as
a striving after a scientific view of the world, yet here is a point of
view--the epistemological--where philosophy is not only independent but
reaches beyond any result of natural science. Perhaps it will be said:
the powers and functions of organic beings only persist (perhaps also
only arise) when they correspond sufficiently to the conditions under
which the struggle of life is to go on. Human thought itself is, then, a
variation (or a mutation) which has been able to persist and to
survive. Is not, then, the problem of knowledge solved by the evolution
hypothesis? Spencer had given an affirmative answer to this question
before the appearance of "The Origin of Species". For the individual, he
said, there is an a priori, original, basis (or Anlage) for all mental
life; but in the species all powers have developed in reciprocity with
external conditions. Knowledge is here considered from the practical
point of view, as a weapon in the struggle for life, as an "organon"
which has been continuously in use for generations. In recent years the
economic or pragmatic epistemology, as developed by Avenarius and Mach
in Germany, and by James in America, points in the same direction.
Science, it is said, only maintains those principles and presuppositions
which are necessary to the simplest and clearest orientation in
the world of experience. All assumptions which cannot be applied to
experience and to practical work, will successively be eliminated.
In these views a striking and important application is made of the idea
of struggle for life to the development of human thought. Thought must,
as all other things in the world, struggle for life. But this whole
consideration belongs to psychology, not to the theory of knowledge
(epistemology), which is concerned only with the validity of knowledge,
not with its historical origin. Every hypothesis to explain the
origin of knowledge must submit to cross-examination by the theory of
knowledge, because it works with the fundamental forms and principles
of human thought. We cannot go further back than these forms and
principles, which it is the aim of epistemology to ascertain and for
which no further reason can be given. (The present writer, many years
ago, in his "Psychology" (Copenhagen, 1882; English translation London,
1891), criticised the evolutionistic treatment of the problem of
knowledge from the Kantian point of view.)
But there is another side of the problem which is, perhaps, of more
importance and which epistemology generally overlooks. If new variations
can arise, not only in organic but perhaps also in inorganic nature, new
tasks are placed before the human mind. The question is, then, if it has
forms in which there is room for the new matter? We are here touching
a possibility which the great master of epistemology did not bring to
light. Kant supposed confidently that no other matter of knowledge could
stream forth from the dark source which he called "the thing-in-itself,"
than such as could be synthesised in our existing forms of knowledge.
He mentions the possibility of other forms than the human, and warns us
against the dogmatic assumption that the human conception of existence
should be absolutely adequate. But he seems to be quite sure that the
thing-in-itself works constantly, and consequently always gives us only
what our powers can master. This assumption was a consequence of Kant's
rationalistic tendency, but one for which no warrant can be given.
Evolutionism and systematism are opposing tendencies which can never
be absolutely harmonised one with the other. Evolution may at any time
break some form which the system-monger regards as finally established.
Darwin himself felt a great difference in looking at variation as an
evolutionist and as a systematist. When he was working at his evolution
theory, he was very glad to find variations; but they were a hindrance
to him when he worked as a systematist, in preparing his work on
Cirripedia. He says in a letter: "I had thought the same parts of the
same species more resemble (than they do anyhow in Cirripedia) objects
cast in the same mould. Systematic work would be easy were it not
for this confounded variation, which, however, is pleasant to me as a
speculatist, though odious to me as a systematist." ("Life and Letters",
Vol. II. page 37.) He could indeed be angry with variations even as
an evolutionist; but then only because he could not explain them, not
because he could not classify them. "If, as I must think, external
conditions produce little DIRECT effect, what the devil determines each
particular variation?" (Ibid. page 232.) What Darwin experienced in
his particular domain holds good of all knowledge. All knowledge is
systematic, in so far as it strives to put phenomena in quite definite
relations, one to another. But the systematisation can never be
complete. And here Darwin has contributed much to widen the world for
us. He has shown us forces and tendencies in nature which make absolute
systems impossible, at the same time that they give us new objects and
problems. There is still a place for what Lessing called "the unceasing
striving after truth," while "absolute truth" (in the sense of a closed
system) is unattainable so long as life and experience are going on.
There is here a special remark to be made. As we have seen above, recent
research has shown that natural selection or struggle for life is no
explanation of variations. Hugo de Vries distinguishes between partial
and embryonal variations, or between variations and mutations, only the
last-named being heritable, and therefore of importance for the origin
of new species. But the existence of variations is not only of interest
for the problem of the origin of species; it has also a more general
interest. An individual does not lose its importance for knowledge,
because its qualities are not heritable. On the contrary, in higher
beings at least, individual peculiarities will become more and more
independent objects of interest. Knowledge takes account of the
biographies not only of species, but also of individuals: it seeks to
find the law of development of the single individual. (The new science
of Ecology occupies an intermediate position between the biography of
species and the biography of individuals. Compare "Congress of Arts and
Science", St Louis, Vol. V. 1906 (the Reports of Drude and Robinson)
and the work of my colleague E. Warming.) As Leibniz said long ago,
individuality consists in the law of the changes of a being. "La loi du
changement fait l'individualite de chaque substance." Here is a world
which is almost new for science, which till now has mainly occupied
itself with general laws and forms. But these are ultimately only means
to understand the individual phenomena, in whose nature and history
a manifold of laws and forms always cooperate. The importance of this
remark will appear in the sequel.