It is expressly devoted to the question--Is Virtue _teachable_?
Sokrates as usual confesses that he does not know what virtue is.

He will not accept a catalogue of the admitted virtues as a definition of virtue, and presses for some common, or defining attribute.

He advances on his own side his usual doctrine that virtue is Knowledge, or a mode of Knowledge, and that it is good and profitable; which is merely an iteration of the Science of good and evil.

He distinguishes virtue from Right Opinion, a sort of quasi-knowledge, the knowledge of esteemed and useful citizens, which cannot be the highest knowledge, since these citizens fail to impart it even to their own sons.
In this dialogue, we have Plato's view of Immortality, which comprises both pre-existence and post-existence.

The pre-existence is used to explain the derivation of general notions, or Ideas, which are antecedent to the perceptions of sense.
In PROTAGORAS, we find one of the most important of the ethical discussions of Plato.