The Megarians, in their first attempts to attain a severer logic, were
making knowledge impossible (compare Theaet.). They were asserting 'the
one good under many names,' and, like the Cynics, seem to have denied
predication, while the Cynics themselves were depriving virtue of all which
made virtue desirable in the eyes of Socrates and Plato. And besides
these, we find mention in the later writings of Plato, especially in the
Theaetetus, Sophist, and Laws, of certain impenetrable godless persons, who
will not believe what they 'cannot hold in their hands'; and cannot be
approached in argument, because they cannot argue (Theat; Soph.). No
school of Greek philosophers exactly answers to these persons, in whom
Plato may perhaps have blended some features of the Atomists with the
vulgar materialistic tendencies of mankind in general (compare Introduction
to the Sophist).

And not only was there a conflict of opinions, but the stage which the mind
had reached presented other difficulties hardly intelligible to us, who
live in a different cycle of human thought. All times of mental progress
are times of confusion; we only see, or rather seem to see things clearly,
when they have been long fixed and defined. In the age of Plato, the
limits of the world of imagination and of pure abstraction, of the old
world and the new, were not yet fixed. The Greeks, in the fourth century
before Christ, had no words for 'subject' and 'object,' and no distinct
conception of them; yet they were always hovering about the question
involved in them. The analysis of sense, and the analysis of thought, were
equally difficult to them; and hopelessly confused by the attempt to solve
them, not through an appeal to facts, but by the help of general theories
respecting the nature of the universe.

Plato, in his Theaetetus, gathers up the sceptical tendencies of his age,
and compares them. But he does not seek to reconstruct out of them a