Liveware Quickies: The Slippery Slope Fallacy

The Slippery Slope Fallacy

…and then it’s turtles all the way down.

The slippery slope fallacy (SSL) is an argument where one sets up a hypothetical chain of premises from an arbitrary point featuring a conclusion that does not follow. Only if this chain of events does not logically follow A->B->C->etc, does it become a fallacy (a subset of Non-Sequitur)
Additionally this fallacy only applies if the argument is made from the “top” or “edge” of the hypothetical slope. If the argument is made from a point on the hypothetical “slope” it is not necessarily to be considered a fallacy as previous steps of the slope already did logically follow.


> If we legalize gay marriage, soon we will need to legalize bestiality and polygamy and ultimately we will have cats and dogs living together in marriage!

This is the classical slippery slope fallacy. The legalization of gay marriage is provided as the arbitrary starting-point (because excluding legalizing inter-racial marriage for example is beneficial to the persons argument). Legalization of bestiality does not directly logically follow from legalizing gay marriage, nor does legalizing polygamy.
Hence the fallacy.

Fun Fact:

> “Fear is the path to the dark side. Fear leads to anger. Anger leads to hate. Hate leads to suffering.”

This famous line from Yoda is a Slippery Slope Fallacy

Fear doesn’t necessarily lead to anger, anger doesn’t necessarily lead to hate, and hate doesn’t necessarily lead to suffering. None of the elements in the chain connect.

Counter Example(s):

> Enabling teaching of creationism in schools would set a dangerous legal precedent that would open the floodgates for all kinds of nonsense being demanded to be taught, like Astrology instead of Astronomy, or Alchemy instead of Chemistry. Science is not a democratic process.

This is -not- a slippery slope fallacy, at least not in the context of the US. The logic is that if a legal precedent is set to occur for one kind of “alternative theory” other “alternative theories” need to be also considered in the curriculum. So B and C follows directly (due to the US legal system) from A.

> If we ban alcohol we would have another prohibition and a resurgence of organized crime.

This is -not- a slippery slope fallacy, there is no slope. The statement might be right or wrong but its not an SSL fallacy.

If an argument becomes an SSL fallacy relies heavily on the logical or empirical proof of the chain from A over B to C.


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