Also Known as: The Camel's Nose.
The Slippery Slope is a fallacy in which a person asserts that some event must inevitably follow from another without any argument for the inevitability of the event in question. In most cases, there are a series of steps or gradations between one event and the one in question and no reason is given as to why the intervening steps or gradations will simply be bypassed.
This argument states that should one event occur it will initiate a chain of events culminating in an undesirable event later. There is no proof made that the undesirable events are caused by the first event.
Definition: In order to show that a proposition P is unacceptable, a sequence of increasingly unacceptable events is shown to follow from P. A slippery slope is an illegitimate use of the "if-then" operator.
This "argument" has the following form:
Event X has occurred (or will or might occur).
Therefore event Y will inevitably happen.
This sort of "reasoning" is fallacious because there is no reason to believe that one event must inevitably follow from another without an argument for such a claim. This is especially clear in cases in which there is a significant number of steps or gradations between one event and another.
"If we legalize marijuana, then more people would start to take crack and heroin, and we'd have to legalize those too. Before long we'd have a nation full of drug-addicts on welfare. Therefore we cannot legalize marijuana."
If we pass
laws against fully-automatic weapons, then it won't be long before we pass
laws on all weapons, and then we will begin to restrict other rights, and
finally we will end up living in a communist state. Thus, we should not
ban fully-automatic weapons.
You should never gamble. Once you start gambling you find it hard to stop. Soon you are spending all your money on gambling, and eventually you will turn to crime to support your earnings.
If I make an exception for you then I have to make an exception for everyone.
Now you say I shouldn't eat cows, tomorrow you'll be saying I shouldn't eat plants.
Identify the proposition P being refuted and identify the final event in the series of events. Then show that this final event need not occur as a consequence of P.