"...it can only find its heroic expression in both becoming slaves."

Most human beings start with certain facts of psychology to which the rest of life must be somewhat related. For instance, every man falls in love; and no man falls into free love. When he falls into that he calls it lust, and is always ashamed of it even when he boasts of it. That there is some connection between a love and a vow nearly every human being knows before he is eighteen. That there is a solid and instinctive connection between the idea of sexual ecstasy and the idea of some sort of almost suicidal constancy, this I say is simply the first fact in one's own psychology; boys and girls know it almost before they know their own language. How far it can be trusted, how it can best be dealt with, all that is another matter. But lovers lust after constancy more than after happiness; if you are in any sense prepared to give them what they ask, then what they ask, beyond all question, is an oath of final fidelity. Lovers may be lunatics; lovers may be children; lovers may be unfit for citizenship and outside human argument; you can take up that position if you will. But lovers do not only desire love; they desire marriage. The root of legal monogamy does not lie (as Shaw and his friends are for ever drearily asserting) in the fact that the man is a mere tyrant and the woman a mere slave. It lies in the fact that if their love for each other is the noblest and freest love conceivable, it can only find its heroic expression in both becoming slaves. I only mention this matter here as a matter which most of us do not need to be taught; for it was the first lesson of life. In after years we may make up what code or compromise about sex we like; but we all know that constancy, jealousy, and the personal pledge are natural and inevitable in sex; we do not feel any surprise when we see them either in a murder or in a valentine.

-George Bernard Shaw (1909)