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Slippery Slope |
| Description: | ||
| The argument tries to defend one extreme position by appealing to the falsity of the opposite extreme. The argument claims that if we abandon the first position, we will inevitably be forced to accept the second, or will eventually come to accept the second for psychological reasons. | ||
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| Examples: | ||
| "We can't allow terminal patients to die without doing everything to save them. If we were to allow that, next we would be permitting euthanasia, and than we would start killing people outright whenever we thought they were no longer valuable to society." | ||
| "Laws prohibiting the possession of handguns are the first step toward robbing us of all our civil liberties!" | ||
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| Discussion: | ||
| In a reductio ad absurdum argument, the arguer
assumes (for the sake of argument) that the opponent's position is true, and
then shows that the consequences of this assumption, taken to its logical
conclusion, is unacceptable. For example, to prove the falsity of the claim
"Ralph can do anything," assume that Ralph can do anything. Then
think of something for Ralph to do that would limit Ralph's ability to do
something else. For example, if Ralph can do anything, then Ralph can build
a wall so tall that no one could jump over it. But if no one can jump over
it, then Ralph can't jump over it, so (since Ralph can do anything) it
follows that Ralph both can and cannot jump over the wall. But this is
absurd; so, the initial assumption that Ralph can do anything must be false. Reductio ad absurdum is a legitimate form of refutation. Statements really do have logical consequences, and where those consequences are unacceptable, the statements themselves must be unacceptable as well. The Slippery Slope fallacy mimics the pattern of the reductio ad absurdum argument. It postulates the truth of an opponent's position, and then tries to make the case that the opponent's position would lead to unacceptable consequences. The Slippery Slope fallacy is illegitimate, however, because the consequences claimed are not actually logical consequences of the opponent's position. Rather, the opponent's position is "connected" to the unacceptable consequences by some other means. Sometimes the argument postulates a (usually improbable) causal sequence of events that would lead from the opponent's position being accepted to the unacceptable consequences. Other times the argument turns on a psychological continuum, i.e. that we will slowly become accustomed to things that we currently find unacceptable. (Such psychological continuums do exist, but movement is rarely only in a single direction, so movement to an unacceptable extreme is never inevitable.) |
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| Classification: A Fallacy of Irrelevance (a deductive fallacy of soundness with a falsehood in the major premiss) in the Middle Ground Fallacies family. | ||
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| Source: I first became aware of this fallacy from Howard Kahane, Logic and Contemporary Rhetoric (1971). Although this is almost certainly not the earliest reference to this fallacy, I have not so far been able to identify an earlier source. Please contact me if you can point me to a potentially useful clue regarding the original source of this fallacy. | ||
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