My research isn't exactly scintillating to the average person. It's an application of concepts from a physical science (geography) to a social one (political science) in an effort to expand what we know about things like partisanship and voter turnout. Oh, but the last sentence of my dissertation is really interesting: "In conclusion, fire up the gas chambers and start killing people."
According to some people, this is the inevitable conclusion of science. It's also one of the most bleedingly obvious examples of a slippery slope argument that you're likely to see.
Slippery slopes are technically a subset of non causa pro causa fallacies, but they're unique in their incremental approach. A standard NC argument asserts (wrongly) that A causes B. The slippery slope asserts that A causes B, which in turn causes C, D, and E, which ultimately causes F. The trick is to get the listener to accept the argument by presenting plausible arguments (banning assault rifles opens the door for other kinds of weapons to be banned) contained in an implausible larger argument (banning assault rifles inevitably leads to a ban on all gun ownership).
Cue Ben Stein. Is he ready? I know I just used him last week, but I think he's rested.
Stein: When we just saw that man, I think it was Mr. Myers [biologist P.Z. Myers], talking about how great scientists were, I was thinking to myself the last time any of my relatives saw scientists telling them what to do they were telling them to go to the showers to get gassed … that was horrifying beyond words, and that’s where science — in my opinion, this is just an opinion — that’s where science leads you.
Crouch: That’s right.
Stein: …Love of God and compassion and empathy leads you to a very glorious place, and science leads you to killing people.
Crouch: Good word, good word.
And there we have it. "Science" leads to killing people. We start with a harmless idea about the evolution of bacteria and, some indeterminate number of steps later, we're gassing people. The argument leaves many questions unanswered, most likely because Mr. Stein is not very good at making arguments. For instance, can we clarify what "science" is? Does geography count? Sociology? Library Science? Second, how many steps are between Librarianship and Genocide? Is there any possibility for intervention before we get to mass murder?
Anton Scalia, dissenting in Lawrence v Texas, approves.
State laws against bigamy, same-sex marriage, adult incest, prostitution, masturbation, adultery, fornication, bestiality, and obscenity are likewise sustainable only in light of Bowers’ validation of laws based on moral choices. Every single one of these laws is called into question by today’s decision; the Court makes no effort to cabin the scope of its decision to exclude them from its holding.
There you have it; if a ridiculous, unenforceable "sodomy" law is repealed and we let teh gays butt-fuck with impunity, it's only a matter of time until incest and man-on-llama are legal.**
The implied undercurrent of every slippery slope argument is "Where will this madness end?" It disregards the human capacity to understand subtle differences (i.e., consenting adults having sex versus someone ass-plowing a barnyard animal) because the authors of such arguments likely lack it. In my experience, the best way to destroy a slippery slope is not by pointing out the illogic (too much effort expended on a dunce who probably won't accept your argument anyway) but simply by turning it around. The next time you hear "If gay marriage is OK, why not polygamy or man-on-dog?" feel free to respond with "OK, if you want to play the slippery slope game, if it's legal to ban gay marriage, why not interracial marriage? Or inter-religious marriage? WHERE DOES IT STOP?!?!?"
You'll feel dirty, but you did it for the greater good.
**Google image search failed me, but this is where I wanted to post a picture of a very worried-looking llama. Turns out they're relatively unflappable.