sychological analysis of knowledge has brought out the
fact of its constant dependence upon practical interests. It is the
need to perform or attain something, which is the motive that leads
to the understanding of things; and the understanding of things with
which alone we are satisfied is commonly that which helps us so to
describe our experience as to be able to control some practical
result. 'Knowledge is power'; and not only so, but in its early stages
and in most of its later developments, knowledge is _for_ power: it is
for purposes of his own that man becomes the 'interpreter of nature.'

It is to men of science rather than to philosophers that we owe the
'descriptive theory' of scientific concepts which, within the last
few years, has gone far to revolutionise the prevailing attitude of
philosophy to science. Concepts, such as 'mass,' 'energy,' and the
like, are no longer held to express realities the denial of which
would be treason to science; they are simply descriptive notions whose
truth consists in their utility: that is to say, in their ability to
comprehend all the relevant facts in a simple description. And, in the
same way, scientific principles are of the nature of postulates, whose
justification is no necessary law of thought, but must rather be
sought in the results of scientific investigation.

These three doctrines--the descriptive theory of science, the
practical nature of knowledge as it is brought out by psychological
analysis, and the special claims of the moral consciousness--have
combined to bring about a tendency strongly opposed to the older
idealist tradition, the tendency to regard practical results as the
sole test of truth.

This conception is put forward now in philosophical literature as
a new and independent point of view. The point of view is only in
process of being hardened into a theory; but, under the name
of Pragmatism, it has already become the subject of a vigorous
propaganda. With the value of this doctrine as a general theory of
reality we need not at present concern ourselves. In spite of the high
claims it makes for the theoretical significance of moral ideas, its
adherents have not as yet devoted much attention to the question of
the worth of these moral ideas and the criteria by which that worth
may be determined. Yet this surely is the fundamental question for
ethical theory. On the other hand, as against a merely theoretical
interpretation of the universe, into w