William Lane Craig's serious response to same sex marriage advocates is to say that if marriage is treated as a social construct (which it is) rather than something with an essence (which it is not), this means 'anything goes', including goat marrying.
In his latest Question of the Week in which he allows that the law should be blind to the sexual orientation of those who want to marry, he says:
Marriage is by its essence a relation between a man and a woman.
The real question here, it seems to me, is whether marriage has an essence or is merely a social construct akin to driving on the right- versus left-hand side of the road. Those who espouse same-sex marriage want to deconstruct marriage so that what counts as marriage is just a matter of convention. Once we start down that route, anything goes: a man and two women, a man and a child, two men and a goat, etc. I see no reason at all to start down that road.This is obviously the slippery-slope fallacy. There really is no more reason for the law to change to allow inter-species marriage after same-sex marriage is recognised than before it. It's revealing that one of the leading apologists for Christianity would resort to such a poor argument.
The history of marriage is the history of a social construct, although to say it is 'merely' a social construct is akin to saying that religion is merely a social construct. Of course it is, but there is more to it. The word represents a vast range of real world activities past and present, and normally it would hardly matter about the word, because it would simply come to also represent marriage between two men or between two women - which it has, for many of us, as a matter of fact. It's interesting that Craig considers the phrase 'gay marriage' misconceived, yet still says:
Laws permitting gay marriage would be clearly unconstitutional, since they would not be blind to the sexual orientation of the persons involved.It's entirely clear what this means; Craig understands that the phrase is readily understood, even if he thinks it misconceived because he thinks marriage has an essence. But, of course, 'marriage' represents something that is going on in society, and it already exists, whether he likes it or not.
So the battle is not to stop marriage from changing; it has changed before and will change again, so the start down the road that Craig so fears has already happened - and it was nothing to do with same sex marriage, note.
The opposition here is just down to good old fashioned religious bigotry, I'm afraid.