e treatises upon Logic and Metaphysics, upon Ethics, Politics,
and Art. He wrote a treatise upon the principles of Rhetoric, another
upon Astronomy, under the title "On the Heavens," another upon
Meteorology. Several of his treatises deal with the biology of animal
life, in which he was intensely interested. They include books
entitled "On the Parts of Animals," "On the Movements of Animals," "On
the Origin of Animals," as well as his great treatise, "Researches on
Animals," which contains an enormous mass of facts collected from
every possible source. It is true that a large proportion of these
facts have turned out to be fictions, but this was inevitable in the
infancy of science. It has been calculated that Aristotle shows
himself acquainted with about five hundred different species of living
beings, though they are not, of course, classified by him in the
modern way. With these books upon animals he founded the science of
Zoology, for no one before his day had made any special study of the
subject.

It has been said that everyone has either an Aristotelian or a
Platonic type of mind. As this implies that Aristotle and Plato are
opposites, it is considerably less than a half truth. No genuine
understanding of Aristotle can endorse the opinion that his
philosophical system was the opposite of Plato's. It would be truer to
say that Aristotle was the greatest of all Platonists, since his
system is still founded upon the Idea, and is an attempt to found an
idealism free from the defects of Plato's system. It is in fact a
development of Platonism. What is the cause then of the popular notion
that {256} Aristotle was the opposite of Plato? Now the fact is that
they _were_ opposites in many important respects. But there was a
fundamental agreement between them which lies deeper than the
differences. The differences are largely superficial, the agreement is
deep-seated. Hence it is the differences that are most obvious, and it
was the differences, too, which were most obvious to Aristotle
himself. The popular opinion arises largely from the fact that
Aristotle never loses an opportunity of attacking the Platonic theory
of Ideas. He is continually at pains to emphasize the difference
between himself and Plato, but says nothing of the agreement. But no
man is a judge of his own deeper relations to his predecessors and
contemporaries. It is only in after years, when the hubbub of
controversy has settled down into the silence o