Slippery Slope: When the Chain of Consequences Is Imaginary

The Anatomy of a Slippery Slope

The slippery slope has this structure: If we allow A, then B will follow. If B occurs, then C will happen. If C happens, then the catastrophic D is inevitable. Therefore, we must not allow A. Each link in the chain is presented as inevitable, but rarely is evidence provided for any of them.

'If we legalize marijuana, next people will demand legalization of cocaine, then heroin, and eventually all drugs will be legal and society will collapse.' Each step in this chain is a separate empirical claim that requires its own evidence. The argument treats the entire chain as a single, inevitable progression.

The persuasive power of the slippery slope comes from fear. By painting a terrifying endpoint, the arguer motivates resistance to the first, usually modest, step. The audience focuses on the catastrophic conclusion rather than critically examining whether the chain of causation is plausible.

When Causal Chains Are Legitimate

Not every prediction of cascading consequences is a slippery slope fallacy. If someone can provide evidence for each link in the causal chain, the argument may be legitimate. The distinction between a fallacious slippery slope and a legitimate causal chain is evidence.

For example: 'If we continue emitting greenhouse gases at current rates, global temperatures will rise. Rising temperatures will melt polar ice. Melting ice will raise sea levels. Rising sea levels will flood coastal cities.' Each step in this chain is supported by substantial scientific evidence. This is a legitimate causal argument, not a slippery slope fallacy.

The test is simple: for each step, ask 'Is there evidence that this step follows from the previous one?' If the answer is yes for every step, the argument is not fallacious. If one or more steps are assumed without evidence, you are looking at a slippery slope.

Countering Slippery Slope Arguments

The most effective counter is to demand evidence for each step in the chain. 'You have claimed that A leads to B leads to C leads to D. Can you provide evidence that B follows from A?' Often, the arguer cannot, because the chain was constructed from fear rather than evidence.

You can also point to real-world examples where the predicted slope did not materialize. Many slippery slope predictions have been historically falsified. Interracial marriage was predicted to destroy the institution of marriage; it did not. This does not prove that all slippery slope arguments are wrong, but it does demonstrate that predicting catastrophic chains is often unreliable.

Another counter is to argue that we can draw lines. Just because we take step A does not mean we are obligated to take step B. Societies draw lines between acceptable and unacceptable all the time. The existence of a spectrum does not mean we cannot choose where to draw the boundary.

• •Slippery slope claims a small action will inevitably lead to extreme consequences.
• •The fallacy lies in asserting inevitability without evidence for each step in the chain.
• •Legitimate causal chains are supported by evidence at each step.
• •Counter by demanding evidence for each link and pointing to historical examples where the slope did not materialize.
• •Societies can and do draw lines -- taking one step does not obligate taking the next.