456 Evolution and Modern Philosophy 
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 con- 
sidered 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 con- 
ditions. 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 suc- 
cessively 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}, 
But there is another side of the problem which is, perhaps, of 
1 The present writer, many years ago, in his Psychology (Copenhagen, 1882; Eng. 
trans]. London, 1891), criticised the evolutionistic treatment of the problem of knowledge 
from the Kantian point of view. 
