Time for another Fallacy Friday. This week's fallacy is often heard by the children of overprotective parents.
Slippery When High
"If we legalize marijuana, then people will join gangs and start taking crack and killing and raping each other! It'll be total anarchy!"
This is a clear example of the reductio ad absurdum, or slippery slope fallacy. The fallacy assumes that if one were to carry the position out to its logical end, that end would be inevitable and possibility harmful. There is no proof made that the harmful end (total anarchy) is caused by the original position (legalizing pot). This is not a way to prove a point, and though it lacks any real reason, the fallacy can be surprisingly tricky--especially in situations where there is a significant number of steps between one event and another.
But the slippery slope isn't always a fallacy. There are a variety of ways to make a slippery slope argument valid, or at least plausible. All you need to do is provide some reason why the adoption of one position will lead to the adoption of another, ie, show your work!
Watch Your Step
The fallacy is often used in emotional situations where careful thought is replaced by an irrational need for illogical proof and justification. We nonbelievers hear this all the time. If you don't believe in God, what's to stop you from killing anyone you want?
The above absurd extrapolation is wrong because it assumes that you need God to be good. Hopefully you, dear reader, will not slide down this hill too.