[P]eople really mean, as I suppose, that the good are like one another, and friends to on another; and that the bad, as is often said of them, are never at unity with one another or with themselves, but are passionate and restless: and that which is at variance and enmity with itself is not likely to be in union or harmony with any other thing.
Here we find Socrates speaking both for himself and for Plato; although it is far from clear just where we might draw the line between the two, this formulation about identity and harmony almost certainly includes elements proper to each of them. The harmony of the soul, and the relationship between this harmony and happy living, appear in many of the Socratic dialogues, reaching their most elaborate treatment in Plato's Republic (a work in which Socrates seems primarily to be a mouthpiece for Plato's own ideas). Here, the context is the discussion of friendship, and specifically the suggestion that friendship is based on likeness. Although it will be concluded soon after this passage that neither the good nor likeness can be the cause of friendship, here those possibilities are still valid. The question is, how do we exclude evil people from the argument that likeness is the basis of friendship (since, presumably, the evil person can be a friend to no one)? Socrates's answer incorporates the idea of the soul as harmonious or dissonant, and puts this idea into play with theories about identity and difference. In a sense, bad people cannot be "like" anyone else because they are not even "like" themselves; whatever harmony draws like to like must first be at work within the single person. Thus, inter-subjective identity (one model of friendship) is prevented by a failure of the evil person to be identical with themselves.