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Slippery slope
Claiming one step inevitably ends in catastrophe, without justifying the chain.
Also known as
Slippery slope argumentThin end of the wedgeDomino fallacy
The shape of the move
If A happens, then B, then C, then D (disaster) — with no reason given that each step must follow.
What is the slippery slope fallacy?
The slippery slope predicts a chain reaction: allow one thing and you'll slide all the way to the worst outcome. The fallacy is not in predicting consequences — it's in assuming every link in the chain is inevitable without evidence.
Each "and then" multiplies uncertainty. Even if every step were 70% likely, a four-step chain would be under 25% likely — yet the argument presents it as certain.
Examples
Politics
“If we legalise cannabis, next it'll be heroin, and soon society collapses.”
Why it fails: No reason is given why each step must follow the last.
Parenting
“If I let you stay up late tonight, you'll be staying up all night every night.”
Why it fails: One exception doesn't make a rule.
In a debate
“Allow AI essays in one class and soon nobody will be able to write.”
Why it fails: The chain from one class to a generation of non-writers is never justified.
Why it feels convincing
Fear of the worst case is powerful, and vivid stories of escalation feel plausible. The audience imagines the end of the slope and forgets to check the steps.
Spot it: A long chain of 'and then…' with no reason each link must follow.
In the arena
If you’re about to commit it
- Justify each link with evidence, not just the first and last.
- Use probability language — "risks", "could" — and explain why.
- Point to real precedents where the chain actually happened.
Instead of
“If we allow one retake, grades will become meaningless.”
Try
“When this university allowed unlimited retakes, average grades rose 11% while employer-tested skills didn't — so retakes risk inflating grades.”
If your opponent commits it
- Ask your opponent to justify the weakest link in the chain.
- Point out where a brake exists (laws, limits, review points).
- Note precedents where the first step didn't lead to the last.
Say this
“Why does step one lead to step four? Each link needs a reason — right now it's just a chain of 'and then'.”
When it’s not a fallacy
If there's real evidence that each step tends to cause the next — a documented precedent or a clear mechanism — warning about the chain is legitimate causal reasoning.
How the Oracle scores it
In an Arguen match, every argument is scored out of 80 across Clarity, Evidence, Logic and Rebuttal. If the Oracle detects a slippery slope, it subtracts a penalty and puts the fallacy on your scorecard with the exact quote and a one-sentence explanation — so you see precisely where the chain snapped.
Frequently asked questions
Is a slippery slope always a fallacy?
No. It's a fallacy when the chain isn't justified. A well-evidenced chain of consequences is a valid argument.
What is a good example of a slippery slope?
"If we let students use calculators, they'll never learn maths, and the economy will collapse." Each step is asserted, not shown.