An introduction to mathematics, by A. N. Whitehead.

172 INTRODUCTION TO MATHEMATICS
number of periodic waves in a vibrating ether,
and the steady sound to similar waves in a
vibrating air. It is not our purpose here to
explain the theory of light or the theory of
sound. We have said enough to make it
evident that one of the first steps necessary
to make mathematics a fit instrument for the
investigation of Nature is that it should be
able to express the essential periodicity of
things. If we have grasped this, we can
understand the importance of the mathematical conceptions which we have next to
consider, namely, periodic functions.