Slippery slope vs false dilemma
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One invents a slide. The other hides the middle.
Slippery slope
A slippery slope says a modest step will lead, without a shown mechanism, to an extreme result. Slopes can be real when each step is likely. The fallacy is the bare claim that one concession dissolves the whole line.
“If students may retake one quiz, they will retake every exam, and then degrees will mean nothing.” No reason is given for why one retake policy forces the rest.
Open the cardFalse dilemma
A false dilemma pretends there are only two options when others are available, or treats the options as if you must take one extreme. Sometimes the pair is real. The fallacy is forcing a pair that has not been shown to be complete.
“Either we keep the museum open every evening, or the town will have no culture at all.” Reduced hours, daytime programmes, and other venues are left out.
Open the cardHow to tell them apart
A slippery slope says a modest step must become an extreme one, without a mechanism for each step. The frightening ending is doing the work.
A false dilemma says there are only two options when the library’s card asks you to name a third. The argument is not the slide. It is the missing door.
You can meet both in one speech: two grim endings, and nothing between them. Split them. Ask what forces the next step, and ask what third option was not mentioned.
FAQ
What is Slippery slope?
A slippery slope says a modest step will lead, without a shown mechanism, to an extreme result. Slopes can be real when each step is likely. The fallacy is the bare claim that one concession dissolves the whole line.
What is False dilemma?
A false dilemma pretends there are only two options when others are available, or treats the options as if you must take one extreme. Sometimes the pair is real. The fallacy is forcing a pair that has not been shown to be complete.
How do you tell Slippery slope from False dilemma?
A slippery slope says a modest step must become an extreme one, without a mechanism for each step. The frightening ending is doing the work.