fferentiation
and process. Such problems can be only abstractly sundered, and the
distinctive character of any metaphysical system will usually consist in
some theory determining their relation. Philosophy returns to these
metaphysical problems with its thought enriched and its method
complicated, after becoming thoroughly alive to the problems of
epistemology, logic, and ethics.

[Sidenote: Epistemology Seeks to Understand the Possibility of
Knowledge.]

Sect. 66. _Epistemology is the theory of the possibility of knowledge_,
and issues from criticism and scepticism. If we revert again to the
history of Greek philosophy, we find a first period of enterprising
speculation giving place to a second period of hesitancy and doubt. This
phase of thought occurs simultaneously with the brilliantly humanistic
age of Pericles, and it is undoubtedly true that energy is withdrawn
from speculation largely for the sake of expending it in the more lively
and engaging pursuits of politics and art. But there are patent reasons
within the sphere of philosophy itself for entailment of activity and
taking of stock. For three centuries men have taken their philosophical
powers for granted, and used them without questioning them. Repeated
attacks upon the problem of reality have resulted in no consensus of
opinion, but only in a disagreement among the wise men themselves. A
great variety of mere theories has been substituted for the old
unanimity of religious tradition and practical life. It is natural under
these circumstances to infer that in philosophy man has overreached
himself. He would more profitably busy himself with affairs that belong
to his own sphere, and find a basis for life in his immediate relations
with his fellows. The sophists, learned in tradition, and skilled in
disputation, but for the most part entirely lacking in originality, are
the new prophets. As teachers of rhetoric and morals, they represent the
practical and secular spirit of their age; while in their avoidance of
speculation, and their critical justification of that course, they
express its sceptical philosophy.

[Sidenote: Scepticism, Dogmatism, and Agnosticism.]

Sect. 67. In their self-justification certain of the sophists attached
themselves to a definite doctrine maintained by those of their
predecessors and contemporaries who were atomists, or followers of that
same Leucippus whom we have quoted. This doctrine was the result of an
attempt to constr