Slippery slope

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This article is about the logical argument. For the novel, see The Slippery Slope. For the film, see Slippery Slope.

A slippery slope argument (SSA), in logic, critical thinking, political rhetoric, and caselaw, is a consequentialist logical device in which a party asserts that a particular result will probably (or even must inevitably) follow from a given decision or circumstance, without necessarily providing any rational argument or demonstrable mechanism for the likelihood of the assumed consequence. A slippery slope argument proposes that a relatively small first step leads to a chain of related events culminating in some significant (usually negative) effect, much like an object given a small push over the edge of a slope sliding all the way to the bottom.[1] The strength of such an argument depends on the warrant, i.e. whether or not one can demonstrate a process that leads to the significant effect. This type of argument is sometimes used as a form of fear mongering, in which the probable consequences of a given action are exaggerated in an attempt to scare the audience. The fallacious sense of "slippery slope" is often used synonymously with continuum fallacy, in that it ignores the possibility of middle ground and assumes a discrete transition from category A to category B. In a non-fallacious sense, including use as a legal principle, a middle-ground possibility is acknowledged, and reasoning is provided for the likelihood of the predicted outcome.

Other idioms for the slippery slope argument are the thin end/edge of the wedge and the camel's nose in the tent.


The argument – an analogy to the effect of gravity and inertia on an object placed on a hillside – takes on one of various semantical forms, generally divisible into the classic formulation and derived usage, either of which may or may not be fallacious depending on the reasoning and evidence presented:

  • In the classical form, the arguer suggests that making a move in a particular direction starts something on a path from which diversion much less reversal will be difficult or impossible. Having started down the metaphorical slope, it will continue to slide in the same direction (the arguer usually sees the direction as a negative one).
  • In derived usage, the argument is that a seemingly minor decision – e.g., to take a particular action, to make a particular rule, or even to refuse to do so as proposed – is predicted to cause a significant (usually undesirable) later impact through a chain of inter-relationships. Establishing this causal series of logical implication (e.g., by quantifying the relevant probabilities step-by-step) becomes more difficult and open to subjective interpretation the longer the chain of reasoning.

The reasoning pattern is also often used in an inverted, positive argument, to imply if this action is taken, then that desirable outcome will be the obvious result; the term "slippery slope" is not often applied directly to this form of the argument.

Consequentialism and unintended consequences[edit]

The core of the slippery slope argument is that a specific decision under debate is likely to result in unintended consequences (and, typically, that they will be worse than either an alternative course of remediation or deferring the decision). The slippery slope (whether in fallacious form or not) is thus consequentialist – i.e., interested in consequences, outcomes or results of a course of action. As such, it does not directly impugn either the character or intentions of the proponent of the idea being labeled a slippery slope. It is also not inherently a criticism of the concerns underlying, or legitimacy of, the taking of a position for or against a rule or course of action.

Non-fallacious usage[edit]

If an argument uses valid reasoning, it would not be identified as the slippery slope fallacy,[2] and the term "slippery slope" may be used without an implying faulty argument. Non-fallacious usage acknowledges the possibility of a middle ground between the initial condition and the predicted result, while providing an inductive argument for the probability of that result versus a middle-ground one, usually based on observation of previous comparable circumstances. This form of the argument is prevalent, under the actual name slippery slope, in United States First Amendment case law, for example.

By definition, any case involving a valid establishment of a positive feedback mechanism constitutes a non-fallacious use of the slippery slope argument, since the slippery slope argument precisely describes a positive feedback mechanism.[3] The argument is fallacious when it is assumed that a certain action behaves with positive feedback without any prior evidence or logical reasoning that it does, but if evidence of a positive feedback mechanism is found, the slippery slope argument may be an accurate description. Positive feedback mechanisms are common in sociology, including positive network effects, and the bandwagon effect.

Both fallacious and valid forms of slippery slope are prevalent in political and public policy debate generally;[4] distinguishing which one is operating in any given argument can be challenging.

See also[edit]


  1. ^ "Learning to Reason Clearly by Understanding Logical Fallacies". July 19, 2007. Archived from the original on February 20, 2012. Retrieved February 20, 2012. 
  2. ^ Lunsford, Andrea; Ruszkiewicz, John (2009). Everything's an Argument. Bedford/St. Martin's. pp. 520–521. ISBN 978-0-312-53862-0. 
  3. ^ Volokh, Eugene (2003), The Mechanisms of the Slippery Slope (PDF), 116 Harv. L. Rev. 1026 2002-2003 
  4. ^ Heinrichs, Jay "Figaro" (February 9, 2006). "Testing Uber Alles". Figures of Speech Served Fresh: In Praise of Argument. 

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