A reader makes an interesting sociological point:
I wonder how much influence the rise of "companionship" marriage has had (and will have) on the acceptance of gay marriage. People like Maggie Gallagher and Ramesh Panunu have argued (correctly) that the principal function of marriage has always been child rearing. That may no longer be true. As life-spans climb into the 80’s, married couples are likely to spend more of their lives as "empty-nesters" than as child-rearers. And while seniors are hardly sexually inactive, there is no doubt but that sexual activity decreases with age. Yet the divorce rate among seniors is significantly less than the rate among couples of child-rearing age. Moreover, the re-marriage rate among seniors who lose their spouses is fairly high, even though there is no chance that the "second marriage" will produce children.
All of this suggests that society is gaining considerable experience with living arrangements where sexual and child-rearing considerations are secondary. And such arrangements appear to work at least as well as child-rearing marriages. As society becomes accustomed to the idea of people living together for the sake of companionship, with sex as a real, but secondary, consideration, the idea of gays living together in committed relationships is likely to seem similar to relationships between older heterosexual couples. Indeed, I suspect that if gay marriage ever becomes widespread, it will be most widespread between couples over 40.
The point of all this is that the nature of an institution, such as marriage, can change through forces having nothing to do with the debates over that institution – in this case, the "graying" of America. And these forces can have unanticipated "side-effects" which can prove far more important than the reasons consciously advanced for and against changes in such an institution.
Absolutely. This, I would argue, is the true conservative position. It’s something Hayek and Burke and Oakeshott would have immediately grasped. A conservative starts not from some a priori doctrine – 
i.e. that "marriage" is for procreation and child-rearing only. He starts from the society he lives in. What does marriage mean now? How has organic social change – the new equality of women, the emergence of openly gay people, the graying of the population, the availability of contraception – made our current arrangements anachronistic? The conservative will then set about – carefully and conservatively – reforming social institutions so that they adapt and coopt the new social realities.
This is the central theme of Burke (along with a deep distrust of power). It’s the essential teaching of Oakeshott. And when you ponder this, you realize that our recent adaptations of the institution of civil marriage – including mixed race couples, gay people, allowing for second marriages as people live longer, seeing marriage as primarily companionate rather than reproductive – are not a means to the destruction or "abolition" of civil marriage, but to its survival in an always-changing society. The theocons are not conservatives in this sense; they are reactionaries. They follow a model of the family that is fixed a priori by theology, and that is oblivious to society as it now is – in fact actively hostile to society as it now is. This mindset was the object of Burke’s scorn; and it was Oakeshott’s primary foe. Yet it now defines a core part of American conservatism. Therein lies the problem.
The Dish 