And now, polygamy. With the sweetly titled HBO series Big Love, polygamy comes out of the closet. Under the headline "Polygamists, Unite!" Newsweek informs us of "polygamy activists emerging in the wake of the gay-marriage movement." Says one evangelical Christian big lover: "Polygamy rights is the next civil-rights battle." Polygamy used to be stereotyped as the province of secretive Mormons, primitive Africans and profligate Arabs. With Big Love it moves to suburbia as a mere alternative lifestyle. As Newsweek notes, these stirrings for the mainstreaming of polygamy (or, more accurately, polyamory) have their roots in the increasing legitimization of gay marriage. In an essay 10 years ago, I pointed out that it is utterly logical for polygamy rights to follow gay rights. After all, if traditional marriage is defined as the union of (1) two people of (2) opposite gender, and if, as gay marriage advocates insist, the gender requirement is nothing but prejudice, exclusion and an arbitrary denial of one's autonomous choices in love, then the first requirement - the number restriction (two and only two) - is a similarly arbitrary, discriminatory and indefensible denial of individual choice. THIS LINE of argument makes gay activists furious. I can understand why they do not want to be in the same room as polygamists. But I'm not the one who put them there. Their argument does. Blogger and author Andrew Sullivan, who had the courage to advocate gay marriage at a time when it was considered pretty crazy, has called this the "polygamy diversion," arguing that homosexuality and polygamy are categorically different because polygamy is a mere "activity" while homosexuality is an intrinsic state that "occupies a deeper level of human consciousness." But this distinction between higher and lower orders of love is precisely what gay rights activists so vigorously protest when the general culture "privileges'' (as they say in the English departments) heterosexual unions over homosexual ones. Was Jules et Jim (and Jeanne Moreau), the classic Truffaut film involving two dear friends in love with the same woman, about an "activity'' or about the most intrinsic of human emotions? To simplify the logic, take out the complicating factor of gender mixing. Posit a union of, say, three gay women all deeply devoted to each other. On what grounds would gay activists dismiss their union as mere activity rather than authentic love and self-expression? On what grounds do they insist upon the traditional, arbitrary and exclusionary number of two? What is historically odd is that as gay marriage is gaining acceptance, the resistance to polygamy is much more powerful. Yet until this generation, gay marriage had been sanctioned by no society that we know of, anywhere at any time in history. On the other hand, polygamy had been sanctioned, was indeed common, in large parts of the world through large swaths of history, most notably the biblical Middle East and through much of the Islamic world. I'M NOT one of those who see gay marriage or polygamy as a threat to or assault on traditional marriage. The assault came from within. Marriage has needed no help in managing its own long slow suicide, thank you. Astronomical rates of divorce and of single parenthood (the deliberate creation of fatherless families) existed before there was a single gay marriage or any talk of sanctioning polygamy. The minting of these new forms of marriage is a symptom of our culture's contemporary radical individualism - as is the decline of traditional marriage - and not its cause. As for gay marriage, I've come to a studied ambivalence. I think it a mistake for society to make this ultimate declaration of indifference between gay and straight life, if only for reasons of pedagogy. On the other hand, I have enough gay friends and feel the pain of their inability to have the same level of social approbation and confirmation of their relationship with a loved one that I'm not about to go to anyone's barricade to deny them that. It is critical, however, that any such fundamental change in the very definition of marriage be enacted democratically and not (as in the disastrous case of abortion) by judicial fiat. Call me agnostic. But don't tell me that we can make one radical change in the one-man, one-woman rule and not be open to the claim of others that their reformation be given equal respect. The writer is a columnist for The Washington Post.