A false cause claims one weak causal link. A slippery slope claims a whole chain of them.
Key idea
A slippery slope argues that one step will set off a chain of events ending in disaster, without good reason to think each link in the chain will happen.
Why it works
A chain is only as strong as its weakest link, and the chances multiply: if each of four links is only somewhat likely, the whole chain is unlikely. Presenting the end as certain hides how weak the links are.
Worked example: Test each link
"If you skip one homework assignment, you'll fall behind, then fail the class, then never get into college."
- Does one missed assignment usually mean falling behind? Not usually.
- Does falling a bit behind mean failing? No.
- The links are weak, and the end is presented as certain.
Answer: Slippery slope.
Worked example: A supported chain
"If you leave the milk out all day, it will warm up. Bacteria grow faster in warm milk. So the milk will likely spoil."
- Does warm milk follow from leaving it out? Yes.
- Do bacteria grow faster when it is warm, and does that spoil milk? Yes: each link is a well-known fact.
Answer: Good reasoning, not a fallacy.
Common mistake
Calling every chain of consequences a slippery slope. Some chains are well supported. The fallacy is a chain of weak or unsupported links presented as though the end were certain. Check each link on its own.