Mark Vernon plumbs Plato for insight on gay marriage:

His dialogue the Symposium is provocative. Perhaps the best known bit is Aristophanes' speech, in which the ancient Greek comic describes humans as originally being wholes who were cut in two by Zeus. That 'explains' why we spend our lives looking for our lost halves.

Interestingly, Aristophanes describes three kinds of aboriginal whole - the hermaphrodite male/female and two kinds of homosexual whole, that after the divine surgery were split into two men and two women respectively. Hence he has a mythical etiology for homosexuality as well as heterosexuality. What might that contribute to the current debate?

Well, it suggests that whilst all humans seek union with the person they come to think of as their other half, they seek differently. Many seek a contrasexual half. Some seek a same-sex half. So within a common quest, there's important variance.

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