Ionian_, the _Italian_, the _Eleatic_, the _Athenian_, and the
_Alexandrian_. In view of their prevailing spirit and tendency, they
have been classified by Cousin as the Sensational, the Idealistic, the
Skeptical, and the Mystical. The most natural and obvious method is that
which (regarding Socrates as the father of Greek philosophy in the
truest sense) arranges all schools from the Socratic stand point, and
therefore in the chronological order of development:

I. THE PRE-SOCRATIC SCHOOLS.
II. THE SOCRATIC SCHOOLS.
III. THE POST-SOCRATIC SCHOOLS.

The history of philosophy is thus divided into three grand epochs. The
first reaching from Thales to the time of Socrates (B.C. 639-469): the
second from the birth of Socrates to the death of Aristotle (B.C.
469-322); the third from the death of Aristotle to the Christian era
(B.C. 322, A.D. 1). Greek philosophy during the first period was almost
exclusively a philosophy of nature; during the second period, a
philosophy of mind; during the last period, a philosophy of life.
Nature, man, and society complete the circle of thought. Successive
systems, of course, overlap each other, both in the order of time and as
subjects of human speculation; and the results of one epoch of thought
are transmitted to and appropriated by another; but, in a general sense,
the order of succession has been very much as here indicated. Setting
aside minor schools and merely incidental discussions, and fixing our
attention on the general aspects of each historic period, we shall
discover that the first period was eminently _Physical_, the second
_Psychological_, the last _Ethical_. Every stage of progress which
reason, on _a priori_ grounds, would suggest as the natural order of
thought, or of which the development of an individual mind would furnish
an analogy, had a corresponding realization in the development of
Grecian thought from the time of Thales to the Christian era. "Thought,"
says Cousin, "in the first trial of its strength is drawn without." The
first object which engages the attention of the child is the outer
world. He asks the "_how_" and "_why_" of all he sees. His reason urges
him to seek an explanation of the universe. So it was in the _childhood_
of philosophy. The first essays of human thought were, almost without
exception, discourses peri physeos (De rerum natura), of the nature of
things. Then the rebound of baffled reason from the impenetrable
bulwarks of th