the first work on the Five
Solids. But no early authority cites the work, the invention of which
may have been easily suggested by the division of roots, which Plato
attributes to him, and the allusion to the backward state of solid
geometry in the Republic. At any rate, there is no occasion to recall
him to life again after the battle of Corinth, in order that we may
allow time for the completion of such a work (Muller). We may also
remark that such a supposition entirely destroys the pathetic interest
of the introduction.

Theodorus, the geometrician, had once been the friend and disciple of
Protagoras, but he is very reluctant to leave his retirement and defend
his old master. He is too old to learn Socrates' game of question and
answer, and prefers the digressions to the main argument, because he
finds them easier to follow. The mathematician, as Socrates says in the
Republic, is not capable of giving a reason in the same manner as the
dialectician, and Theodorus could not therefore have been appropriately
introduced as the chief respondent. But he may be fairly appealed to,
when the honour of his master is at stake. He is the 'guardian of his
orphans,' although this is a responsibility which he wishes to throw
upon Callias, the friend and patron of all Sophists, declaring that
he himself had early 'run away' from philosophy, and was absorbed in
mathematics. His extreme dislike to the Heraclitean fanatics, which may
be compared with the dislike of Theaetetus to the materialists, and his
ready acceptance of the noble words of Socrates, are noticeable traits
of character.

The Socrates of the Theaetetus is the same as the Socrates of the
earlier dialogues. He is the invincible disputant, now advanced in
years, of the Protagoras and Symposium; he is still pursuing his divine
mission, his 'Herculean labours,' of which he has described the origin
in the Apology; and he still hears the voice of his oracle, bidding him
receive or not receive the truant souls. There he is supposed to have
a mission to convict men of self-conceit; in the Theaetetus he has
assigned to him by God the functions of a man-midwife, who delivers men
of their thoughts, and under this character he is present throughout the
dialogue. He is the true prophet who has an insight into the natures
of men, and can divine their future; and he knows that sympathy is the
secret power which unlocks their thoughts. The hit at Aristides, the son
of Lysimachus, w