Eros is an issue of boundaries. He exists because certain boundaries do. In the interval between reach and grasp, between glance and counterglance, between 'I love you' and 'I love you too,' the absent presence of desire comes alive. But the boundaries of time and glance and I love you are only aftershocks of the main, inevitable boundary that creates Eros: the boundary of flesh and self between you and me. And it is only, suddenly, at the moment when I would dissolve that boundary, I realize I never can.

Infants begin to see by noticing the edges of things. How do they know an edge is an edge? By passionately wanting it not to be. The experience of eros as lack alerts a person to the boundaries of himself, of other people, of things in general. It is the edge separating my tongue from the taste for which it longs that teaches me what an edge is. Like Sappho's adjective glukupikron, the moment of desire is one that defies proper edge, being a compound of opposites forced together at pressure. Pleasure and pain at once register upon the lover, inasmuch as the desirability of the love object derives, in part, from its lack. To whom is it lacking? To the lover. If we follow the trajectory of eros we consistently find it tracing out this same route: it moves out from the lover toward the beloved, then ricochets back to the lover himself and the hole in him, unnoticed before. Who is the real subject of most love poems? Not the beloved. It is that hole.

When I desire you a part of me is gone: my want of you partakes of me. So reasons the lover at the edge of eros. The presence of want awakens in him nostalgia for wholeness. His thoughts turn toward questions of personal identity: he must recover and reincorporate what is gone if he is to be a complete person. The locus classicus for this view of desire is the speech of Aristophanes in Plato's Symposium. Here Aristophanes accounts for the nature of human eros by means of a fantastic anthropology (189d-93d). Human beings were originally round organisms, each composed of two people joined together as one perfect sphere. These rolled about everywhere and were exceedingly happy. But the spherical creatures grew overambitious, thinking to roll right up to Olympus, so Zeus chopped each of them in two. As a result everyone must now go through life in search of the one and only other person who can round him out again. "Sliced in two like a flatfish," says Aristophanes, "each of us is perpetually hunting for the matching half of himself" (191d).

Most people find something disturbingly lucid and true in Aristophanes' image of lovers as people cut in half. All desire is for a part of oneself gone missing, or so it feels to the person in love. Aristophanes' myth justifies that feeling, in typical Greek fashion, by blaming the whole situation on Zeus. But Aristophanes is a comic poet. We might look, for a more serious exegesis, to more serious lovers. A feature of their reasoning will at once strike us. It is outrageous.