Slippery slope

A series of statements that have a superficial connection with one another, and which lead into what is often a rather far-fetched conclusion.

In a slippery slope argument, a course of action is rejected because the slippery slope advocate believes it will lead to a chain reaction resulting in an undesirable end or ends. The core of the slippery slope argument is that a specific decision under debate is likely to result in unintended consequences.

Example:

If we ban smoking, then people will start taking soft drugs and then move onto hard drugs, and the crime rate will go up and up. We should therefore prevent crime by allowing smoking.

The slippery slope is particularly obvious in its lack of real reason, yet it appears surprisingly often. It is often used in emotional situations where careful thought is replaced by an irrational need for illogical proof and justification.

This fallacy is often used by politicians. This is possibly because they tend to be risk-averse, and the slippery slope seems like a good way of pointing out dangers.