This dialogue is known by several different names -- Lovers (Erastai) and Rival Lovers (Anterestai) both go back a long way. One occasionally finds it subtitled, On Philosophy. It's important to keep in mind, if one is to interpret the dialogue correctly, that the erastēs is primarily a mentor, although Greek custom allowed, and indeed generally expected, that there was a precise kind of sexual relationship involved; as long as one recognized the latter (and the link to eros, desire), one could also translate the terms as 'Mentors' or 'Rival Mentors'. It is in fact rivalry in mentorship that is in view in the dialogue.
Since Schleiermacher, who held that everything in the dialogue indicated its spuriousness, it has generally been considered spurious on stylistic and vocabulary grounds, although in the past thirty years, due to a famous paper by Julia Annas, there has been an increasing tendency to think that, like Alcibiades, the case against it is weak, although perhaps (on grounds of vocabulary and grammar) stronger than the case against Alcibiades. According to Ledger, it is stylometrically much closer to Xenophon than Plato. On the assumption that it is not by Plato but by a student of Plato, it has sometimes been suggested (implausibly, I think) that the dialogue may be an attack on the somewhat polymathic approach of Aristotle; but it has also been suggested that Aristotle might be rejecting a key claim of this dialogue in Politics 1252a7-9,in which he says that it is not the same to be a statesman, head of a household, or a master of slaves.
You can read Rival Lovers online at the Perseus Project.
(in order of appearance)
Four unnamed youths
The Plot and The Thought
Socrates narrates how he walked into the school of Dionysus the grammarian and found there two young men arguing about natural philosophy. Their erastai were there, as well, and, sitting down next to one of them, Socrates remarks that they must be discussing something interesting and admirable.
The young man he directed the comment to, who is a jock, replied that they were merely "babbling about things up in the sky and talking philosophical nonsense" (132b). Socrates asks him why he holds philosophy in such contempt. At this point, his rival, who is a geek, replied that Socrates was wasting his time, since the jock does nothing but wrestle, eat, and sleep.
Socrates asks the geek whether he thinks that philosophy is admirable. At this point the two boys who were arguing come over to listen to the discussion, and so the geek replies, somewhat self-consciously and with a gesture at the jock in order to make a point to the audience that if he ever thought philosophy to be contemptible, he would no longer consider himself a human being. Socrates responds that if he thinks it is admirable, he must know what it is, and asks what it might be, to which the rival youth replies that it is polymathy.
Using the analogy between learning and athletics to pit the two against each other in an indirect way, Socrates is able to draw out the point that what is good and admirable must be moderate. Sensing that he's about to lose the interest of the boys, however, he shifts his approach and asks what kinds of things a philosopher would need to learn. The geek replies that the philosopher is supposed to train so as to appear to be expert in every craft, or, failing that, in the most important ones, focusing on theory rather than practice. When Socrates questions whether this is even possible, the geek replies that the philosopher only needs to know what is reasonable for a free man, so that he can understand the specialists more than other people.
Socrates compares this to the pentathlete who never excels at any task but is always only second-best at everything -- unable to place first, but still doing better than everyone else. The geek agrees that this is an appropriate analogy. Socrates asks whether the good people are useful or useless, and the geek replies that they are useful. He then asks whether philosophers are useful, and the geek replies that they are useful.
Socrates then points out the oddity of this. If you are sick, what's useful is a doctor, not the philosopher who has studied some medical theory. If you are on a ship in stormy weather, what you want is the pilot, not a philosopher who has studied some of the theory of navigation. And this is true for every kind of craft down the line. But civilized people will pretty much always have the specialists available, so philosophers seem to be useless. But, Socrates says, philosophers are not polymaths, but something quite different.
As he always does, Socrates brings the matter around to justice, which he argues requires knowing good human beings from bad human beings and knowing which one is, as a temperate person. And the just person governs the city well, and the household well, and himself well: it is all the same craft or skill. And this is the skill a philosopher should cultivate, and he should strive to excel at it, not settle for being second-best like the pentathlete.
Thus Socrates silences the geek; the jock says that he's right; and the others admire the argument.
* The theme that justice requires temperance or self-control is a very common one throughout the Platonic dialogues.
* The inscription of the Delphic Oracle, Know Thyself, is explicitly brought in and given a Platonic explanation: "it is this, it seems, which is prescribed, in the Delphic inscription, to exercise good sense [sophrosyne = temperance] and justice [dikaiosyne]"(138a).
* The structure here is perhaps a bit more subtle than it might seem: Socrates has managed to manipulate the situation so as to benefit everyone. The geek gets no more harm from being corrected on the subject than shame at having been wrong in front of his favorite, but now he will have a better view of the subject he already recognizes as important. In the meantime, by refuting the geek, with whom he might superficially have been expected to agree, he has interested the jock in the subject, and given the jock a view of philosophy that makes it something other than nonsense. The other boys have stopped arguing over astronomy and learned something, as well.
In the manuscripts, the dialogue is always called Erastai, Lovers, but the word anterestai, which is sometimes preferred by ancient lists of the dialogues, is found in the dialogue itself, and is very appropriate. But one of the things we can see in the dialogue is that there is a contrast between the rivalrous love of the two mentors and philosophy as love of wisdom: philosophy is a form of love but its love is nonrivalrous. Indeed, practiced Socratically it eliminates rivalries and benefits everyone involved.
Quotations from Jeffrey Mitscherling's translation in Plato, Complete Works, Cooper and Hutchinson, eds., pp. 618-626.