Photo by Kamil Krzaczynski/Reuters

Just this past Monday, Jillian Keenan wrote an article in Slate titled “Legalize Polygamy!”  She writes:

While the Supreme Court and the rest of us are all focused on the human right of marriage equality, let’s not forget that the fight doesn’t end with same-sex marriage. We need to legalize polygamy, too. … Divorce, remarriage, surrogate parents, extended relatives, and other diverse family arrangements mean families already come in all sizes—why not recognize that legally? … As women, we really can make our own choices. We just might choose things people don’t like. If a woman wants to marry a man, that’s great. If she wants to marry another woman, that’s great too. If she wants to marry a hipster, well—I suppose that’s the price of freedom.  And if she wants to marry a man with three other wives, that’s her damn choice.

All marriages deserve access to the support and resources they need to build happy, healthy lives, regardless of how many partners are involved. Arguments about whether a woman’s consensual sexual and romantic choices are “healthy” should have no bearing on the legal process. And while polygamy remains illegal, women who choose this lifestyle don’t have access to the protections and benefits that legal marriage provides.

The definition of marriage is plastic. Just like heterosexual marriage is no better or worse than homosexual marriage, marriage between two consenting adults is not inherently more or less “correct” than marriage among three (or four, or six) consenting adults. Though polygamists are a minority—a tiny minority, in fact—freedom has no value unless it extends to even the smallest and most marginalized groups among us. So let’s fight for marriage equality until it extends to every same-sex couple in the United States—and then let’s keep fighting. We’re not done yet.

Ms. Keenan is not saying something radical.  She’s merely pointing out what others choose to ignore: If A should be legal because of X, and X also applies to B, then B should also be legal.  If same-sex marriage becomes legal, it is virtually inevitable that polygamy will follow.  If marriage can be made to mean anything, it will become anything and everything.