The Symposium by Plato (-385)

Once, Aristophanes says, we were not single but double, round creatures with four arms and four legs, so strong the gods grew afraid and split us in two, and ever since each half has wandered the earth aching for the other. That is one speech at one drinking party in Athens, where the wine goes round and the guests agree to take turns praising Love. The speeches rise and contradict each other until Socrates repeats what a priestess once taught him: that desire is not having but wanting, that we love only what we lack, and that this same hunger, followed up its long ladder, can carry a soul from one beautiful body to the sheer idea of beauty. Then Alcibiades reels in drunk and garlanded with violets, and confesses he loved Socrates and could not have him. _The Symposium_ is where the West first tried to say what longing is for, and it has never said it better.