Once upon a time, human beings were of three kinds: male, female, and androgynous. They had four hands, four legs, and two faces on a single head on a single neck. Zeus split each of these human beings in two, and so each half longed for its other. Aristophanes explains it all in Plato’s Symposium:
“This, then, is the source of our desire to love each other. Love is born into every human being: it calls back the halves of our original nature together; it tries to make one out of two and heal the wound of human nature. . . .Happy Valentine’s Day to all.
“[W]e used to be complete wholes in our original nature, and now ‘love’ is the name for our pursuit of wholeness, for our desire to be complete.”
[Translation by Alexander Nehemas and Paul Woodruff (Hackett, 1989).]