the hero of the battle of Corinth and of the dialogue, is
a disciple of Theodorus, the great geometrician, whose science is thus
indicated to be the propaedeutic to philosophy. An interest has been
already excited about him by his approaching death, and now he is
introduced to us anew by the praises of his master Theodorus. He is a
youthful Socrates, and exhibits the same contrast of the fair soul and
the ungainly face and frame, the Silenus mask and the god within, which
are described in the Symposium. The picture which Theodorus gives of
his courage and patience and intelligence and modesty is verified in
the course of the dialogue. His courage is shown by his behaviour in the
battle, and his other qualities shine forth as the argument proceeds.
Socrates takes an evident delight in 'the wise Theaetetus,' who has more
in him than 'many bearded men'; he is quite inspired by his answers. At
first the youth is lost in wonder, and is almost too modest to speak,
but, encouraged by Socrates, he rises to the occasion, and grows full of
interest and enthusiasm about the great question. Like a youth, he has
not finally made up his mind, and is very ready to follow the lead of
Socrates, and to enter into each successive phase of the discussion
which turns up. His great dialectical talent is shown in his power of
drawing distinctions, and of foreseeing the consequences of his own
answers. The enquiry about the nature of knowledge is not new to him;
long ago he has felt the 'pang of philosophy,' and has experienced the
youthful intoxication which is depicted in the Philebus. But he
has hitherto been unable to make the transition from mathematics to
metaphysics. He can form a general conception of square and oblong
numbers, but he is unable to attain a similar expression of knowledge
in the abstract. Yet at length he begins to recognize that there are
universal conceptions of being, likeness, sameness, number, which the
mind contemplates in herself, and with the help of Socrates is conducted
from a theory of sense to a theory of ideas.

There is no reason to doubt that Theaetetus was a real person, whose
name survived in the next generation. But neither can any importance be
attached to the notices of him in Suidas and Proclus, which are probably
based on the mention of him in Plato. According to a confused statement
in Suidas, who mentions him twice over, first, as a pupil of Socrates,
and then of Plato, he is said to have written