Regardless of what one thinks of the gay rights/defense of marriage debate, this much should be unassailable:

“If marriage is redefined, its connection to organic bodily union and thus to procreation will be undermined. It will increasingly be understood as an emotional union for the sake of adult satisfaction that is served by mutually agreeable sexual play. But there is no reason that primarily emotional unions like friendships should be permanent, exclusive, limited to two, or legally regulated at all. Thus, there will remain no principled basis for upholding marital norms like monogamy.

A veneer of sentiment may prevent these norms from collapsing but only temporarily. The marriage culture, already wounded by widespread divorce, nonmarital cohabitation and out-of-wedlock childbearing will fare no better than it has in those European societies that were in the vanguard of sexual ‘enlightenment…’

Candid and clear-thinking advocates of redefining marriage recognize that doing so entails abandoning norms such as monogamy. In a 2006 statement entitled Beyond Same-Sex Marriage, over 300 lesbian, gay, and allied activists, educators, lawyers, and community organizersincluding Gloria Steinem, Barbara Ehrenreich, and prominent Yale, Columbia and Georgetown professorscall for legally recognizing multiple sex partner (polyamorous) relationships. Their logic is unassailable once the historic definition of marriage is overthrown.”

– Robert P. George, Gay Marriage, Democracy and the Courts, Wall Street Journal, August 3, 2009.

When Professor George says that “norms such as monogamy” will be abandoned, I take him to be referring to the historically prevailing cultural attitude that sex is only permissible within a married relationship. I do not think, though perhaps I am wrong, that he means to say that non-traditional (e.g., polyamorous, temporary, or otherwise non-monogamous) relationships will replace monogamous relationships as the “norm.” Although non-traditional relationships will doubtless increase, they will increase only insofar as there is demand for them, and something in the human makeup seems to drive the great bulk of us towards a desire for monogamy. Instead, I take Professor George to mean that non-traditional relationships will become “normalized” in the sense that they will be accepted and the stigma against them removed or reduced.

Viewed in this light, the comments quoted above seem unassailable. The question is not whether this will happen, but simply whether it has already happened (as a consequence of the divorce, cohabitation, and out-of-wedlock child bearing he mentions) and, if so, whether it can or should be reversed.

(As always, I do need to add the caveat, per Stanley Fish, that there is not and never has been a “principled basis” for upholding marriage norms, if by “principled” one means a basis which is distinct from the substantive values one holds and wishes to impose on the world.)