Why even bother? Why bother thinking about it at all, since it seems pretty clear that it isn't going to be stopped. A large segment of the country, including those all-powerful federal judges, have accepted the dogma that defining marriage as a union of two people of opposite sexes is morally and intellectually identical to racism. In a few months the matter will come before our nine popes without a God, and it seems likely that they, in their recently-adopted role as law-givers to the tribe, will declare that every state must adopt the official view that there is no difference between heterosexuality and homosexuality.
So why not just let it go, quit talking about it, and try to keep one's distance from the new order? Because this is not just a change in the language on marriage licenses, and a means of allowing homosexual couples to adopt children, or to be counted as relatives for the purposes of hospital visits and the like, or to get the tax benefits of marriage. It is a redefinition of some fundamental aspects of what it means to be human, and although many of its effects will be slow to develop, they will be profound.
One of the most obvious effects, and one that probably won't take long to become visible, is a change in the relationship of Christianity to the state in post-Christian societies. There is an excellent piece at First Things on that subject, The Civic Project of American Christianity. Thanks to Rob G for pointing it out. Here's a sample:
...we must see that the sexual revolution is not merely—or perhaps even primarily—sexual. It has profound implications for the relationship not just between man and woman but between nature and culture, the person and the body, children and parents. It has enormous ramifications for the nature of reason, for the meaning of education, and for the relations between the state, the family, civil society, and the Church. This is because the sexual revolution is one aspect of a deeper revolution in the question of who or what we understand the human person to be (fundamental anthropology), and indeed of what we understand reality to be (ontology).
All notions of justice presuppose ontology and anthropology, and so a revolution in fundamental anthropology will invariably transform the meaning and content of justice and bring about its own morality. We are beginning to feel the force of this transformation in civil society and the political order. Court decisions invalidating traditional marriage law fall from the sky like rain. The regulatory state and ubiquitous new global media throw their ever increasing weight behind the new understanding of marriage and its implicit anthropology, which treats our bodies as raw material to be used as we see fit. Today a rigorous new public morality inverts and supplants the residuum of our Christian moral inheritance.
This compels us to reconsider the civic project of American Christianity that has for the most part guided our participation in the liberal public order for at least a century.
One of the reasons the redefinition of marriage is succeeding is that the arguments for it are simple and emotionally appealing and deal with the immediate satisfaction of desires and the immediate resolution of difficult situations. Who wants to be the mean old person saying "no" to those nice lesbians who want to adopt a baby together, especially if he is going to be publicly despised and perhaps punished for it? The arguments against it, on the other hand, deal with bigger and less immediately personal matters, and are based on long-term implications and effects. But it's just because we are losing the political battle that it is important to understand what is happening, and what is likely to happen in the coming decades.
Same-sex marriage is an attempt to deny, by linguistic and legal fiat, the fundamental reality of sexuality and the social structures which stem from it. In the long run, reality will reassert itself. In the meantime, it may be difficult at times to resist acquiescence in official falsehoods. We're going to need clear heads.
Addendum: a long statement of the case, also at First Things, by Evangelicals and Catholics Together, with a notable list of signees.