In conversation with Socrates, Meno asks whether virtue can be taught. Socrates suggests that the two of them are to determine whether virtue can be taught, they must first define clearly what virtue is.
Meno first suggests that different kinds of virtue exist for different kinds of people. Socrates replies that Meno’s definition is like a swarm of bees: each kind of virtue, like each bee, is different, but Socrates is interested in that quality they all share. Meno next suggests that virtue is being able to rule over people, but Socrates dismisses this suggestion on two grounds: first, it is not virtuous for slaves or children to rule over people, and second, ruling is virtuous only if it is done justly. This response prompts Meno to define virtue as justice. But he then concedes to Socrates that justice is a form of virtue but not virtue itself.
Struggling with Socrates’ demands for a definition, Meno asks him to give an example of definitions of shape and color. Socrates first gives a straightforward definition of shape (“the limit of a solid”) and then an elaborate definition of color in the style of the sophists, which shows up their empty pretentiousness.
Meno attempts to define virtue again, suggesting that it involves desiring good things and having the power to secure them, but only if one does so justly. However, this definition again encounters the problem of using “justice” in a definition of virtue: we cannot define something by using an instance of what it is we are defining.
Meno compares Socrates to a torpedo fish, which numbs anything it touches. Socrates has struck Meno dumb, and Meno no longer knows what to say. If they don’t even know what virtue is, he asks, how are they to know what to look for?
Socrates responds that learning is not a matter of discovering something new but rather of recollecting something the soul knew before birth but has since forgotten. To show what he means, he calls over one of Meno’s slave boys, draws a square with sides of two feet, and asks the boy to calculate how long the side of a square would be if it had twice the area of the one he just drew. The boy suggests four feet and then three feet, and Socrates proves him wrong both times. Socrates then helps the boy recognize that a square of twice the area would have sides with a length equal to the diagonal of the present square—but Socrates leads the boy to this point without actually explaining anything, instead forcing the boy to think the problem through himself. Since the boy reached this conclusion (more or less) on his own without any direct teaching, he must have been recollecting something he already knew.