many conservative persons in his day a dangerous one; he was regarded
as an innovator; he taught men to think and to raise questions where,
before, the traditions of the fathers had seemed a sufficient guide to
men's actions.

And, indeed, he could not do otherwise. Men had learned to reflect,
and there had come into existence at least the beginnings of what we
now sometimes rather loosely call the mental and moral sciences. In
the works of Socrates' disciple Plato (428-347 B.C.) and in those of
Plato's disciple Aristotle (384-322 B.C.), abundant justice is done to
these fields of human activity. These two, the greatest among the
Greek philosophers, differ from each other in many things, but it is
worthy of remark that they both seem to regard the whole sphere of
human knowledge as their province.

Plato is much more interested in the moral sciences than in the
physical, but he, nevertheless, feels called upon to give an account of
how the world was made and out of what sort of elements. He evidently
does not take his own account very seriously, and recognizes that he is
on uncertain ground. But he does not consider the matter beyond his
jurisdiction.

As for Aristotle, that wonderful man seems to have found it possible to
represent worthily every science known to his time, and to have marked
out several new fields for his successors to cultivate. His philosophy
covers physics, cosmology, zoölogy, logic, metaphysics, ethics,
psychology, politics and economics, rhetoric and poetics.

Thus we see that the task of the philosopher was much the same at the
period of the highest development of the Greek philosophy that it had