The US Court of Appeals for the First Circuit in Boston struck a glancing blow for marriage equality Thursday with a unanimous ruling against the 1996 Defense of Marriage Act. The court declared that the denial of federal benefits to legally married gay couples that are available to married heterosexual couples is unconstitutionally discriminatory. The court did not rule on the larger question whether state laws against same-sex marriage are unconstitutional but logic would seem to lead inexorably in this direction.

And yet, states continue to pass laws banning gay marriages. Earlier this month North Carolina became the 30th state to do so. That is only eight states fewer than what would be required to write the prohibition into the United States Constitution.

The Circuit Court in Boston was apparently persuaded by Massachusetts Attorney General Martha Coakley’s argument that DOMA “discriminates against our citizens” – which is clearly true since Massachusetts is one of the handful of states that recognizes gay marriage – and that there is no “rational basis for the statute” – which is arguably false.

Former Republican presidential hopeful Rick Santorum spoke for many conservatives on this issue. When challenged to defend his opposition to gay marriage, Santorum has replied, “Well, if two men can marry, then why not three men?” This is a clever riposte. While same sex marriages are gaining increasing support, perhaps even approaching majority support, among the public at large, almost no one is in favor of multiple spouses.

Santorum’s argument can be taken in two ways, both of which are effective from a rational point of view. It may be construed as reduction ad absurdum. If we reject the notion that marriage is by definition the union of one man and one woman, and accept the legitimacy of same sex marriages, then logic compels us to accept the legitimacy of multiple spouses. If ‘man’ and ‘woman’ are arbitrary limitations, then so too are ‘one’ man and ‘one’ woman. And since multiple spouses are clearly unacceptable, then same-sex marriages must also be unacceptable.

The argument can also be understood as a version of the so-called slippery slope. Logical considerations aside, and human nature being what it is, if we accept same-sex marriages today, tomorrow we will be accepting multiple marriages.

This is likely what those who believe that gay marriage “threatens the institution of marriage” and thus somehow threatens their marriages, worry about. Better not to step onto that slope.

How does an advocate for same-sex marriages respond to these arguments? One possibility is to simply accept the consequences, as unpalatable as they may be. Absent a religious or cultural impulse, multiple marriages are not very likely to catch on. I’m reminded here of the quip that gay people ought to be allowed to marry because they have every right to be as miserable as straight couples. Marriage is hard enough for two people to sustain; imagine how hard it would be for three or four or five.

A different response has been put forward by public figures as far apart politically as the libertarian Ron Paul and the legal scholar and public intellectual Cass Sunstein, a high placed official in Obama White House.

Government should get out of the marriage business altogether. Government should be in the civil union business. Civil unions are contractual arrangements between two (or more, why not?) consenting adults. Like any other legal contract, they ought to be recognized by the state and enforced by the appropriate civil authority. Civil unions involving more than two people may be more complicated than traditional unions, but that is no reason to disallow them. Our legal system is equipped to handle complexity.

Marriage is a sacrament. Marriages are spiritual relationships, vows of honor that should be anointed and enforced by religious authority. Virtually all religions practiced in the United States today define marriage as the union of one man and a one woman. This is likely to remain the cultural norm for the foreseeable future. The recently passed Maryland statute legalizing same-sex marriages wisely accommodates this fact by explicitly empowering churches to refuse to perform them.

Yes, there are some religions, like the United Church of Christ, that recognize and bless same sex marriages. And yes, there are some fringe religions, like Mormon Fundamentalism, that recognize and bless and, indeed, encourage multiple marriages. Let a thousand flowers bloom; neither is a threat to your marriage or to the Republic.

Marriage doesn’t need to be defended. It doesn’t need to be re-defined. It simply needs to be removed from the purview of the state.

David Tebaldi is executive director of Mass Humanities.