AP® English Language and Composition · Logical Fallacies in Reasoning
Slippery Slope: The Chain With a Missing Link
A slippery slope argument claims one small step will inevitably trigger a chain of worse ones, ending in disaster, without showing that each step actually makes the next one likely.
The appeal works on fear, not logic. 'And then where does it end' feels like a argument because it paints a vivid ending, a diploma that means nothing, a city rationing water, and lets the dread of that ending stand in for proof. But a chain is only as strong as its weakest link, and a slippery slope skips the welding at every joint. It asserts that step one leads to step two, step two to step three, without ever showing why each move is probable rather than merely imaginable.
Take the lunch-phones argument: allow phones at lunch, then in class, then nobody graduates. The chain fails at the very first joint. Allowing phones at lunch does not make allowing them in class more likely; a school can draw that line easily, and nothing about the first policy forces the second. No evidence connects any two links, which is exactly the fallacy's signature.
Not every predicted chain is fallacious. The hydrologist's reservoir argument moves from low water to lost pump suction to rationing, but each joint is backed by a year it actually happened. That evidence is what separates a legitimate causal chain from a slippery slope: real slopes can exist, the fallacy is calling a chain inevitable when no one has shown the links hold. This is the same standard a cause-effect paragraph needs, each causal claim earns its place with evidence, not momentum from the sentence before it.
Key terms
- Slippery slope
- An argument that a small first step will inevitably lead through a chain to an extreme outcome, without evidence for each link.
- Joint
- The point in a chain argument where one claimed step is supposed to cause or lead to the next.
- Causal chain
- A sequence of cause-and-effect claims; legitimate when each link has its own supporting evidence.
- Burden of proof
- The obligation to supply evidence for a claim rather than assuming it from the force of the narrative.
Watch it explained
- How it worksHow does a slippery slope chain small steps together and skip the probability at every joint?
- Worked exampleShow me which step fails in 'Allow phones at lunch, then in class, then nobody graduates.'
- Common mistakeWhy isn't every chain of predicted consequences a slippery slope fallacy?
- Going furtherWhat makes a slope argument legitimate once each individual step carries its own evidence?
- Ties togetherHow does a slippery slope relate to the causal chains a cause-effect paragraph is built from?
Check yourself
End of topic.