A long time ago, there were three kinds of human beings: male, descended from the sun; female, descended from the earth; and androgynous, with both male and female elements, descended from the moon. Each human being was completely round, with four arms and fours legs, two identical faces on opposite sides of a head with four ears, and all else to match. They walked both forwards and backwards and ran by turning cartwheels on their eight limbs, moving in circles like their parents the planets.
As they were powerful and unruly and threatening to scale the heavens, Zeus (the king of the gods) devised to cut them into two ‘like a sorb-apple which is halved for pickling,’ and even threatened to cut them into two again, so that they might hop on one leg. Apollo (the god of light) then turned their heads to make them face towards their wound, pulled their skin around to cover up the wound, and tied it together at the navel like a purse. He made sure to leave a few wrinkles on what became known as the abdomen so that they might be reminded of their punishment.
After that, human beings longed for their other half so much that they searched for it all over and, when they found it, wrapped themselves around it very tightly and did not let go. As a result, they started dying from hunger and self-neglect, and Zeus took pity on them, and moved their genitals to the front so that those who were previously androgynous could procreate, and those who were previously male could obtain satisfaction and move on.
This is the origin of our desire for other human beings; those of us who desire members of the opposite sex were previously androgynous, whereas men who desire men and women who desire women were previously male or female. When we find our other half, we are ‘lost in an amazement of love and friendship and intimacy’ that cannot be accounted for by a simple desire for sex, but rather by a desire to be whole again and restored to our original nature. Our greatest wish, if we could have it, would then be for Hephaestus (the god of fire) to melt us into one another so that our souls could be at one, and share in a common fate.
Plato, Symposium, The Myth of Aristophanes (c. 400 BC)