We have these two different understandings of human sexuality: the hedonistic, self-indulgent understanding, the self-interested one; and the one that has procreation at its heart, and that is characterized by the need to acknowledge responsibility and obligation. And just so no one will miss the point: the reason that homosexuality epitomizes the [first] one is that homosexuals are not haunted by the prospect or possibility of procreation - because they're simply not capable of it. I think this is pretty obvious, isn't it? And it was understood in human society at one point that if you're not capable of procreation, marriage doesn't have anything to do with you, because marriage is about procreation.