Ian Millhiser brings up Justice Ginsburg's argument in favor of gay marriage:
[Same-sex couples] wouldn't be asking for this relief if the law of marriage was what it was a millennium ago. I mean, it wasn't possible.
Same-sex unions would not have opted into the pattern of marriage, which was a relationship, a dominant and a subordinate relationship.
Yes, it was marriage between a man and a woman, but the man decided where the couple would be domiciled; it was her obligation to follow him.
There was a change in the institution of marriage to make it egalitarian when it wasn’t egalitarian. And same-sex unions wouldn't -- wouldn't fit into what marriage was once.
Ian goes on: the law "presumed that the wife was both financially and sexually subservient to the husband. ... But marriage is no longer bound to antiquated gender roles. And when those gender roles are removed, the case for marriage discrimination breaks down."
Now first of all, let's admit that while marriage is a Catholic sacrament, and may save one's soul, and many other wonderful things, the civil or common law is not concerned with such subtle matters of divine grace but with more mundane issues of human nature, that is, of man as he (and she) is in his own natural state. As a result, how marriage is to be conceived should be discussed by considering solely natural law.
And regarding that, marriage exists in law to order human reproduction. There are two aspects of it: unitive or the relations between the husband and wife; and procreative or the relations between the parents and children.
The unitive aspect of civil marriage is to discourage faithless love, thereby promiscuity, thereby heartbreak. Both men and women benefit tremendously from the stability, sexual, emotional, intellectual, that marriage brings to their lives and frees them to pursue happiness rightly understood, and the law is concerned to foster such stability.
I mean, who can doubt that until a man marries a woman, he is essentially desperate and capable of all manner of self- and other-destructive things?
For male homosexuals, there is no love, even faithless kind: it's all about lust: the very idea that two gays can fall in love with each other defies reason. Lesbianism may be different; but lesbianism seems so preposterous that it only makes sense in pornography. So, the unitive function of marriage is not served by "equality."
The procreative aspect of civil marriage is to assure legitimacy, that children are biologically one's own, and provide a home for those children that features both unconditional nurturing from the mother and conditional guidance from the father.
But gays cannot have children, at least at the current level of biotechnology. Nor are they capable of providing a suitable home for adopted children; therefore, even with adoption properly privatized, no adoption agency can be permitted to send its kids to homosexuals.
It is these concerns, and not whether the wife should or should not be "financially and sexually" subservient to the husband that suggest that society ought not to recognize gay marriage as an institution as special as normal marriage.