Carving nature at its joints

Socrates: It seems to me that the discourse was, as a whole,really sportive jest; but in these chance utterances were involved two principles, the essence of which it would be gratifying to learn, if art could teach it.

Phaedrus: What principles?

Socrates: That of perceiving and bringing together in one idea the scattered particulars, that one may make clear by definition the particular thing which he wishes to explain; just as now, in speaking of Love, we said what he is and defined it, whether well or ill. Certainly by this means the discourse acquired clearness and consistency.

Phaedrus: And what is the other principle, Socrates?

Socrates: That of dividing things again by classes, where the natural joints are, and not trying to break any part, after the manner of a bad carver. As our two discourses just now assumed one common principle, unreason, and then, just as the body, which is one, is naturally divisible into two, right and left, with parts called by the same names, so our two discourses conceived of madness as naturally one principle within us, and one discourse, cutting off the left-hand part, continued to divide this until it found among its parts a sort of left-handed love, which it very justly reviled, but the other discourse, leading us to the right-hand part of madness, found a love having the same name as the first, but divine, which it held up to view and praised as the author of our greatest blessings.

—Plato, Phaedrus, 264-6