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

DYNAMICS 47
use of a lever, and also from a consideration of
various problems connected with the weights
of bodies. It was finally put on its true basis
at the end of the sixteenth and during the
seventeenth centuries, as the preceding account shows, partly with the view of explaining the theory of falling bodies, but chiefly
in order to give a scientific theory of planetary
motions. But since those days dynamics has
taken upon itself a more ambitious task, and
now claims to be the ultimate science of which
the others are but branches. The claim
amounts to this: namely, that the various
qualities of things perceptible to the senses
are merely our peculiar mode of appreciating
changes in position on the part of things
existing in space. For example, suppose we
look at Westminster Abbey. It has been
standing there, grey and immovable, for centuries past. But, according to modern scientific theory, that greyness, which so heightens
our sense of the immobility of the building,
of itself nothing but our way of appreciating
the rapid motions of the ultimate molecules,
which form the outer surface of the building
and communicate vibrations to a substance
called the ether. Again we lay our hands on
its stones and note their cool, even temperature, so symbolic of the quiet repose of the
building. But this feeling of temperature
simply marks our sense of the transfer of