Slippery slope

Slippery-Slope Sam

“One tiny step and it's avalanches all the way down!”

What's the problem?

A slippery-slope argument says one step will lead to further steps and a serious outcome. Such arguments are not automatically fallacious: a careful forecast explains how each step leads to the next and points to support. The fallacy is an unsupported slope, an escalating chain whose links have no stated reasons or evidence. Unsupported escalation can be a problem even when it is phrased only as a possibility, so "could" does not repair it, and "will" does not prove a fallacy. Exploring a possibility in order to investigate it is not automatically a fallacy either. A modest, plausible concern does not need numerical evidence. Check each link: what connects this step to the next, and is that connection supported?

Context: A neighbor objects to a proposal to let food trucks park on Main Street on Fridays.

✗ Unsupported slope

If we allow food trucks on Fridays, restaurants will close, downtown will empty out, and the town will go bankrupt.

✓ Supported concern

I am concerned about possible effects on nearby restaurants' Friday sales. The council should examine likely effects before deciding.

Why it works

The revision keeps the concern about restaurant sales and asks for those effects to be examined. It drops the unsupported jump to closures and bankruptcy, and it invents no evidence.