he distinction between sense and reason, must yet find
room for their identity, and must show that sense is but a lower form
of reason. This idea Aristotle thoroughly understood, and sought to
show, not merely that sense is reason, but even that the activities of
inorganic matter, such as gravitation, are so. In the result, nature,
though working through reason, is not conscious of the fact, does so
blindly and instinctively, and is compared to a creative artist, who
forms beautiful objects by instinct, or, as we should say, by
inspiration, without setting before his mind the end to be attained or
the rules to be observed in order to attain it.

{291}

In the process of nature, it is always form which impels, matter which
retards and obstructs. The entire world-movement is the effort of form
to mould matter, but, just because matter has in itself a power of
resistance, this effort does not always succeed. This is the reason
why form cannot exist without matter, because it can never wholly
overcome the clogging activity of matter, and therefore matter can
never be wholly moulded into form. And this explains, too, the
occasional occurrence in nature of freaks, monstrosities, abortions,
and unnatural births. In these the form has failed to mould the
matter. Nature has failed to attain her ends. Science, therefore,
should study the normal and natural rather than the abnormal and
monstrous. For it is in the normal that the ends of nature are to be
seen, and through them alone nature can be understood. Aristotle is
fond of using the words "natural" and "unnatural," but he uses them
always with this special meaning. That is natural which attains its
end, that in which the form successfully masters the matter.

No doctrine of physics can ignore the fundamental notions of motion,
space, and time. Aristotle, therefore, finds it necessary to consider
these. Motion is the passage of matter into form, and it is of four
kinds. The first is motion which affects the substance of a thing,
origination and decease. Secondly, change of quality. Thirdly, change
of quantity, increase and decrease. Fourthly, locomotion, change of
place. Of these, the last is the most fundamental and important.

Aristotle rejects the definition of space as the void. Empty space is
an impossibility. Hence, too, he disagrees with the view of Plato and
the Pythagoreans that {292} the elements are composed of geometrical
figures. And connected with this is his