Simon Critchley in The NYT's The Stone:
[H]ow are we to understand the nature of eros as it appears in Plato’s “Phaedrus”? And here we approach the central enigma of the dialogue. For it appears to deal with two distinct topics: eros and rhetoric. My thought is very simple: I will try and show that these twin themes of eros and rhetoric are really one and they help explain that peculiar form of discourse that Socrates calls philosophy.
For the ancient Greeks, there was obviously a close connection between the passions or emotions, like eros, and rhetoric. We need only recall that Aristotle’s discussion of the emotions is in the “Rhetoric.” Emotion was linked to rhetoric, for Aristotle, because it could influence judgment, in the legal, moral or political senses of the word.
Of course, in the Athens of Socrates’ time, the two groups of people capable of stirring up powerful emotions were the tragic poets and the Sophists. Let’s just say that Socrates had issues with both groups. Tragedy, again in Aristotle’s sense, stirs up the emotions of pity and fear in a way that leads to their katharsis, understood as purgation or, better, purification. The Sophists exploited the link between emotion and rhetoric in order to teach the art of persuasive speech that was central to the practice of law and litigation. Classical Athens was a very litigious place, but mercifully did not have lawyers. Therefore, men (and it was just men) had to defend themselves and Sophists taught those who could pay a fee how to do it.
More here.