Back when our country was still debating whether or not we should change the definition of marriage to include same-sex couples, those opposed to the redefinition argued that if we did so, polygamy and polyamory would be next. Opponents argued that this was a crazy slippery slope fallacy. But it wasn’t. It was a valid slippery slope argument. Conservatives were simply noting that the rationale for redefining marriage to include same-sex couples applied equally to all sorts of other relationships, including polygamy and polyamory. If you include same-sex couples, there is no rational basis on which to exclude polygamy. The idea that marriage should be limited to just two people is based on the sex binary. Once the sex binary is replaced with a simple requirement of “love and commitment,” polygamous and polyamorous relationships qualify for marriage as well.

(more…)