In order to show that a proposition P is unacceptable, a sequence of increasingly unacceptable events is shown to follow from P. A slippery slope is an illegitimate use of the "if-then" operator. This fallacy, a subgenre of the appeal to consequence, is also known as "The camel’s nose". "In a typical slippery slope argument, an action is objected to on the grounds that once it is taken, another, and then perhaps still another, are bound to be taken, down a ‘slippery slope,’ until some undesirable consequence results. According to a slightly different version, whatever would justify taking the first step would also justify all the others, but since the last step isn’t justified, the first isn’t, either." (Kahane & Cavender, Logic and Contemporary Rhetoric, p. 84)
- "If abortion on demand were to become legal, there would be a great increase in abortions. And once abortion became commonplace, there would be a weakening of respect for human life in general. Once the respect for human life was weakened, we would see an increase in euthanasia of all kinds: the elderly, the mentally handicapped, and the physically disabled. Before long we would be getting rid of anyone who is unproductive. In short, it would threaten our civilization. Therefore, we should oppose any move to broaden the grounds for legal abortions." (Hughes & Lavery, Critical Thinking, pp. 167-8.)
- "One of the arguments against court-ordered desegregation of the schools was that if we allow the court to determine which public schools our children will attend, the court will also tell us whom we have to allow into our churches, whom we have to invite into our homes, and even whom we should marry. In this example, the action (court-ordered desegregation) lies on a continuum with the court ordering whom we should marry at an extreme end. The argument being made is that if we allow the court to have jurisdiction over events at one end of the continuum, then it will take over the other events on the continuum." (Halpern, Critical Thinking Across the Curriculum, p. 128.)
- "The more disaster-prone prevention education contains the 'logical' statement that any form of drinking (especially by young people) will lead to more drinking and will eventually result in death. Aside from its inaccuracy, most students who hear this warning are not impressed and may scoff at the whole notion. Mot people in the world drink and the drinking does not increase pathologically or end in premature death. In fact, some data indicate that a drink or two is good for you." (Taleff, Critical Thinking for Addiction Professionals, p. 108.)
- If I make an exception for you then I have to make an exception for everyone.
- "Whether a causal type of domino effect is reasonable depends on the strength or plausability of the evidence given to support the causal linkages proposed at each step. The classic case of the domino effect argument was its use during the Vietnam War era to argue that, if Vietnam fell to the Communists, then neighboring countries like Cambodia would also fall. Then, other adjacent countries would fall until the whole of East Asia would be in Communist hands. This argument was often used as a kind of scare tactic by its exponents, and because not much evidence seemed available to back it up very firmly, it came to be thought of as a fallacious type of argument, in this particular instance." (Walton, Informal Logic, pp. 268-9.)
Identify the proposition P being refuted and identify the final event in the series of events. Then show that this final event need not occur as a consequence of P.