“While important legal and practical questions remain unresolved, with the Supreme Court’s ruling and broad public support, marriage equality is here to stay. Soon, it will be time to turn the attention of social liberalism to the next horizon. Given that many of us have argued, to great effect, that deference to tradition is not a legitimate reason to restrict marriage rights to groups that want them, the next step seems clear. We should turn our efforts towards the legal recognition of marriages between more than two partners. It’s time to legalize polygamy.”

Traditional marriage supporters have long made the case that the argument for gay marriage can also be used to advance polygamous marriage. Chief Justice John Roberts agrees on page 22 of his powerful dissent:

Although the majority randomly inserts the adjective “two” in various places, it offers no reason at all why the two-person element of the core definition of marriage may be preserved while the man-woman element may not. Indeed, from the standpoint of history and tradition, a leap from opposite-sex marriage to same-sex marriage is much greater than one from a two-person union to plural unions, which have deep roots in some cultures around the world. If the majority is willing to take the big leap, it is hard to see how it can say no to the shorter one.

And now just today, Politico has a long-form think-piece making the case for polygamy. Here’s an excerpt:

Polyamory is a fact. People are living in group relationships today. The question is not whether they will continue on in those relationships. The question is whether we will grant to them the same basic recognition we grant to other adults: that love makes marriage, and that the right to marry is exactly that, a right…

While important legal and practical questions remain unresolved, with the Supreme Court’s ruling and broad public support, marriage equality is here to stay. Soon, it will be time to turn the attention of social liberalism to the next horizon. Given that many of us have argued, to great effect, that deference to tradition is not a legitimate reason to restrict marriage rights to groups that want them, the next step seems clear. We should turn our efforts towards the legal recognition of marriages between more than two partners. It’s time to legalize polygamy.

The next stage of the sexual revolution always seems implausible until it is no longer implausible. Here we are. It turns out that the slope is indeed slippery.

Denny Burk is Associate Professor of New Testament and Dean of Boyce College, the undergraduate arm of the Southern Baptist Theological Seminary. This article first appeared on his blog and is used with permission.