ion; 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 theory of knowledge. The time at which such a theory could be framed
had not yet arrived. For there was no measure of experience with which
the ideas swarming in men's minds could be compared; the meaning of
the word 'science' could scarcely be explained to them, except from the
mathematical sciences, which alone offered the type of universality and
certainty. Philosophy was becoming more and more vacant and abstract,
and not only the Platonic Ideas and the Eleatic Being, but all
abstractions seemed to be at variance with sense and at war with one
another.

The want of the Greek mind in the fourth century before Christ was
not another theory of rest or motion, or Being or atoms, but rather a
philosophy which could free the mind from the power of abstractions
and alternatives, and show how far rest and how far motion, how far the
universal principle of Being and the multitudinous principle of atoms,
entered into the composition of the world; which could distinguish
between the true and false analogy, and allow the negative as well as
the positive a place in human thought. To such a philosophy Plato, in
the Theaetetus, offers many contributions. He has followed philosophy
into the region of mythology, and pointed out the similarities of
opposing phases of thought. He has also shown that extreme abstractions
are self-destructive, and, indeed, hardly distinguishable from one
another. But his intention is not to unravel the whole subject of
knowledge, if this had been possible; and several times in the course
of the dialogue he rejects explanations of knowledge which have germs of
truth in them; as, for example, 'the reso