Slippery Slope: The Unproven Chain Reaction

Evaluate arguments that predict a series of escalating consequences from one small step.

A slippery slope argument claims that one step will inevitably lead to a chain of increasingly bad outcomes. It becomes a fallacy when the links in the chain are asserted without evidence. Worked example: 'If we let students use calculators on this quiz, soon they won't learn arithmetic at all, then they'll fail math, and eventually they won't be able to manage their own money. ' Each step may be possible, but none is shown to be likely, let alone inevitable. The argument's force comes from the frightening endpoint, not from proof of the links.

To evaluate a slope, examine each link separately: is there evidence that A leads to B, and B to C? Also consider stopping points; rules and decisions can usually be limited. Some chains are real; evidence may show that a small policy change reliably triggers others. The difference between a reasonable warning and a fallacy is whether each link is supported.

• 1A slippery slope predicts an escalating chain of consequences.
• 2It is fallacious when the links lack evidence.
• 3Evaluate each link separately and look for stopping points.