In logic class, I was taught that the “slippery slope” argument was a fallacy.

And logically, it is. It’s essentially if x then y, with no supporting arguments.

From a practical standpoint, it’s true that one argument can open the door for another argument to be considered. Arguing about Obamacare, for example, might open the door to arguments on the single-payer system. (Even though Obama himself slammed that door in his interview with Marc Maron.)

And so we hear a lot about the “slippery slope” in politics. You hear it a lot in gun arguments. “Oh, if we register our guns, then the government will start rounding them all up.” (Those arguments also inevitably invoke Hitler.)

But with gun laws, we’ve already seen that we can block the slippery slope. The USA has some restrictions on the right to bear arms. I can’t take the Metro down to Northrop Grumman and purchase a fully loaded A-10 Thunderbolt, yet such limitations mean little to owners of hunting rifles. The National Firearms Act of 1934 was amended in 1968, which is bad news for grenade owners but hasn’t eliminated handguns for the country.

So with gay marriage, we’ve already seen the slippery slope question: What about polygamy? Naturally, Politico came out and trolled everyone with that argument, though I don’t know of a serious movement to legalize it.

You may not want polygamy – neither do I – but what you can’t do is argue that you can’t allow gay marriage because polygamy inevitably follows. As we’ve seen in gun rights, the next step on the slope isn’t inevitable.

What you have to do is much harder. You have to create the intellectual and legal argument against polygamy itself. 

And if you’ve taken any philosophy classes, you know that it’s difficult to make such arguments against actions that don’t have obvious victims. You can argue against pedophilia and bestiality using a “consent” argument. It’s much more difficult to argue against something that takes place among consenting adults. Today’s fashionable libertarianism would say people should be able to define a family however they want. I’ve been pondering polygamy for a while, and the only argument I can find about harm to society is that it would lead to fewer guys marrying more women, leaving a lot of guys out in the cold. And there’s nothing more dangerous to society than guys that can’t get laid.

(Remember the urban legends about how Bin Laden was radicalized? American women laughed at him, and off he went. That’s surely a joke, but I think there’s some truth to the notion that people who are content with their love lives are a little less prone to irrational violence.)

But seriously – the fact that I haven’t come up with a good argument against polygamy doesn’t mean that it doesn’t exist. I’m sure someone smarter than me can come up with it.

And if we’re going with slippery slopes, consider this – putting “under God” on our currency, as we did in the 1950s, is the first step toward sharia law, Christian style.