Definition · Plain-language
Slippery slope
A slippery slope argument claims that one relatively small first step will inevitably lead to a chain of events ending in some extreme outcome.
The step most authors miss
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Why the chain matters
The slippery slope takes the form "if we allow A, then B will follow, then C, until we reach disastrous Z". The fallacy lies not in considering consequences but in assuming, without justification, that each link in the chain is inevitable. Often the intermediate steps are merely possible, not probable, yet the argument treats the final extreme outcome as a certainty. The persuasive force comes from fear of the worst-case ending, which distracts from the missing evidence that the steps would in fact occur.
Causal and conceptual versions
There are two common forms. The causal slippery slope claims that one event will physically or socially cause a sequence of further events. The conceptual (or precedent) slippery slope claims that accepting one case logically commits you to accepting increasingly extreme cases, because no clear line can be drawn. Both can be legitimate or fallacious; the question in each is whether the claimed connection between steps is actually supported, or merely asserted to provoke alarm.
When it is not a fallacy
Not every slippery slope argument is fallacious. If there is real evidence that one step tends to lead to the next — for example, documented precedent, incentives or mechanisms making the progression likely — then warning about a slope is legitimate causal reasoning. The fallacy occurs only when the inevitability of the chain is assumed without support. Evaluating a slippery slope therefore means examining each claimed link: is it shown to follow, or simply assumed?
Key facts
At a glance
- Definition: claiming one step inevitably leads to extreme consequences
- Type: informal fallacy (of weak induction / unsupported causation)
- Key flaw: the inevitability of the chain is assumed, not shown
- Two forms: causal slippery slope and conceptual (precedent) slope
- Persuasive lever: fear of the worst-case final outcome
- Not fallacious when: each step is genuinely supported by evidence
Common misconceptions
What people often get wrong
Often heard: Any argument about future consequences is a slippery slope fallacy.
Actually: Reasoning about consequences is normal and often necessary. It becomes the slippery slope fallacy only when the chain of events is asserted to be inevitable without evidence that each step actually follows. A well-supported causal forecast is legitimate.
Often heard: A slippery slope is fallacious because predicting the future is impossible.
Actually: The flaw is not that it predicts, but that it assumes inevitability without justification. Where there is genuine evidence — precedent, incentives, mechanisms — that one step leads to the next, a slippery slope argument can be perfectly reasonable.
Often heard: Pointing out a slippery slope settles the argument in your favour.
Actually: Labelling something a slippery slope does not by itself refute it. You must show that the claimed steps are not in fact inevitable. If the chain is well supported, calling it a "slippery slope" is just a name, not a rebuttal.
Going deeper
