sign of difference, I have
knowledge. But have I knowledge or opinion of this difference; if I
have only opinion I have not knowledge; if I have knowledge we assume
a disputed term; for knowledge will have to be defined as right opinion
with knowledge of difference.

And so, Theaetetus, knowledge is neither perception nor true opinion,
nor yet definition accompanying true opinion. And I have shown that the
children of your brain are not worth rearing. Are you still in labour,
or have you brought all you have to say about knowledge to the birth? If
you have any more thoughts, you will be the better for having got rid of
these; or if you have none, you will be the better for not fancying that
you know what you do not know. Observe the limits of my art, which, like
my mother's, is an art of midwifery; I do not pretend to compare with
the good and wise of this and other ages.

And now I go to meet Meletus at the porch of the King Archon; but
to-morrow I shall hope to see you again, Theodorus, at this place.

...

I. The saying of Theaetetus, that 'Knowledge is sensible perception,'
may be assumed to be a current philosophical opinion of the age. 'The
ancients,' as Aristotle (De Anim.) says, citing a verse of Empedocles,
'affirmed knowledge to be the same as perception.' We may now examine
these words, first, with reference to their place in the history of
philosophy, and secondly, in relation to modern speculations.

(a) In the age of Socrates the mind was passing from the object to the
subject. The same impulse which a century before had led men to form
conceptions of the world, now led them to frame general notions of the
human faculties and feelings, such as memory, opinion, and the like. The
simplest of these is sensation, or sensible perception, by which Plato
seems to mean the generalized notion of feelings and impressions of
sense, without determining whether they are conscious or not.

The theory that 'Knowledge is sensible perception' is the antithesis of
that which derives knowledge from the mind (Theaet.), or which assumes
the existence of ideas independent of the mind (Parm.). Yet from their
extreme abstraction these theories do not represent the opposite poles
of thought in the same way that the corresponding differences would
in modern philosophy. The most ideal and the most sensational have a
tendency to pass into one another; Heracleitus, like his great successor
Hegel, has both aspects. The Eleatic i