http://www.youtube.com/watch?v=2EUBvFZgAx4&feature=watch_response
Now this one’s kind of tricky. In use, it might not actually be a fallacy. It depends. Here’s the pattern.
“Well, if event A happens, what’s to stop event B from happening? And if event B happens, what’s to stop event C? And then what’s to stop event D and E and F? And suddenly we’re in totally different territory.”
That’s the pattern. Here’s the logical structure.
First premise: Event A sets off a chain reaction that leads inexorably or almost inexorably to event Z.
Second premise: Event Z is something unfavorable.
Conclusion: In the interests of preventing Z we should prevent A.
The key question here is, does event A have any actual bearing, as far as we can tell, on the odds of event B, C, and D, etc? Is the first premise well founded? Maybe it is. For example, when I was in grade school, one day, the teacher assigned us a book report, and she insisted that the book we used as a subject had to be at least 100 pages; maybe more, but not a single page less. Not even one. After all, she explained, making such an allowance was virtually guaranteed to set this sequence in motion.
first student: “Well, 97 pages is close to 100.”
second student: “Well, 93 pages is close to 97.”
third student: “Well, 89 pages is close to 93.”
And the next thing you know, we have students writing reports on books only 15 pages long. Do I doubt the likelihood of this sequence? Not at all. I dare to say that this teacher gave the assignment this stipulation out of her own acquaintance with the psychology of the typical grade-school student.
Now let’s look at the age-old dilemma of the parent of a teenager.
“Heh heh. Sure, Son. Your girlfriend can come over to study in your room, but you keep that door open while she’s here. Do you understand me, young man? Keep it open or I’ll remove it.”
Does this make sense? Is it prudent for the parent to impose this boundary? Of course. Why? Because one thing tends to lead to another. This first step is, indeed, onto a slippery slope. In this particular setting, this observation (one thing leads to another) has predictive power. Here we have another non-fallacious slippery slope.
“Teenagers. You give them an inch and they walk all over you.”
Here’s another non-fallacious example:
“If today you can take a thing like evolution and make it a crime to teach it in the public school, tomorrow you can make it a crime to teach it in the private schools, and the next year you can make it a crime to teach it to the hustings or in the church. At the next session you may ban books and the newspapers. Soon you may set Catholic against Protestant and Protestant against Protestant, and try to foist your own religion upon the minds of men. If you can do one you can do the other. Ignorance and fanaticism is ever busy and needs feeding. Always it is feeding and gloating for more. Today it is the public school teachers, tomorrow the private. The next day the preachers and the lectures, the magazines, the books, the newspapers. After [a]while, your honor, it is the setting of man against man and creed against creed until with flying banners and beating drums we are marching backward to the glorious ages of the sixteenth century when bigots lighted fagots to burn the men who dared to bring any intelligence and enlightenment and culture to the human mind.”
This is a quote from Clarence Darrow, at the Scopes Monkey trial, defense council for a biology teacher named John Scopes who was taken to court for having the audacity to teach evolution. Now how about another historical example?
The expansion of the Japanese Empire, during World War II was driven by an odd kind of circular reasoning. They needed to expand their territory so that they could obtain more material resources. But they needed to obtain more material resources so that they could expand their territory. Therefore, though I don’t know if it actually happened, many voices of reason and prudence would have been well founded in concluding that, in the event the Japanese Empire was allowed to expand a little, they would subsequently expand a little more, and a little more, and next thing you know, even if they started clear on the other side of the world, they are now threatening your territory and/or the territory of friends and allies of yours.
Here’s a non-fallacious example I would like all my Muslim subscribers to make note of, given the growing popularity among Muslims of Holocaust denial. The Holocaust is a widely and heavily documented historical event. To deny it is to deny and abuse history.
Among the world’s most famous holocaust deniers, and by that I mean people famous specifically for their holocaust denial—those who’ve made a career out of it with virtually no attention to anything else—a significant portion are not Muslim. What’s to stop these people from turning right around tomorrow and denying that Mohammed ever existed?
One also finds a psychological slippery slope in Germany , leading up to the Holocaust. The powers that be in that country, in 1930, would not have been able to get away with the Holocaust then, but instead had to be content with much more minor injustices, and then slightly less minor, and then slightly less and slightly less, incrementally more and more severe, until we have a holocaust.
Now how about a few fallacious examples?
“If you teach people they are biologically related to animals, won’t they start acting like animals?”
This slippery slope is kind of short, but still fallacious. First, although most animals are not people, all people are animals. To be human is to be a pattern-seeking primate; one particular species of animal. Therefore, to act like a human is to act like an animal; albeit a particular species. But second, you mean other species of animals, don’t you? Any species in particular? I mean one thing evolution shows us is that human beings are biologically related to kangaroos. Are you telling me that, if you came to accept evolution, you would start to act like one of them? I would like to see that.
You can’t allege behavior like animals with any meaning unless you are prepared to specify what species of animal. Camels are animals too. Does this mean that accepting evolution will lead to people acting like camels? What about goldfish, jellyfish, moths, anemones, or choral? These are all animals and these all have very distinctly different behavioral characteristics. If the act of accepting evolution leads to animal behavior, what species?
Just to digress for a moment, I mentioned anemones there. I don’t understand why anyone has a difficult time pronouncing this word (anemone). I mean you pronounce it the same way you would pronounce these four letters (N M N E) in this sequence. Simple. Now back to the subject.
“Well, if you legalize same-sex marriage today, you’ll be legalizing bestiality tomorrow, then pedophilia, then vandalism, then murder, and so on and so on, until you get to ethnic cleansing, and soon the whole world will be consumed in flames!”
How in the world do you figure that? How in the world does restricting same-sex marriage mitigate the occurrence of any of the rest of these? A number of states in my country alone have legalized same-sex marriage. Has this brought any change at all in the amount of political pressure brought to bear by bestiality-rights groups? What laws are there, currently, against bestiality? How are they enforced? How could they be enforced except by a complete, utter, total disregard for privacy in any form?
“If you permit scientists to destroy human embryos for the purpose of research, it's a slippery slope from there to killing human fetuses in order to harvest tissue, and from there to euthanizing disabled or terminally ill people to harvest their organs, and from there to human cloning and human-animal hybrids, and if making chimeras is okay, well then Dr. Frankenstein must also be okay, and Dr. Mengele, too, and before you know it, it's one long hapless inevitable slide from high-minded medicine to the Nazis.”
Of course. Nazism has so much to do with stem-cell research, euthanasia, cloning and making chimeras, doesn’t it? After all, those mad scientists in Saturday Morning cartoons which are always making chimeras are all Nazis, aren’t they? The very same argument could be made about the slippery slope from legalizing mustaches into Bolshevism.
So the key question here is how great are the odds that each event in the proffered sequence actually facilitates the occurrence of subsequent events? How much veracity is there to the first premise in this argument?
Incidentally, this drawing of a slippery slope into fascism, Nazism, Communism, Maoism and such is a very common practice. You could almost call it hackneyed and predictable.