ence. ¹ Mach ² says, "Every philosopher has his
own private science and every scientist his pri-
vate philosophy," intimating that both are
rather crude affairs. May we not make of these
two a blend, retaining a little of the creativeness
of science, even with some of its naïveté, and of
the breadth of philosophy, even with some of its
scepticism?

To give any sort of historical account of the
development of scientific concepts would re-
quire more space than is allotted to these pages
and a competence far surpassing my own. What
I shall attempt to present will be a kind of con-
temporaneous cross section showing the inner
structure of science. Such a presentation must
of necessity have a somewhat personal bias. I
know that I shall say many things that have
been said before, often by authors unknown to
me, but I shall console myself with the hope that
one or two of the things that I say here will, in
their turn, be said again.

I should have liked to use the word 'meta-
physics' in the title of this book, but there are

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