Slippery slope

[citation needed] When the initial step is not demonstrably likely to result in the claimed effects, this is called the slippery slope fallacy.

Other idioms for the slippery slope fallacy are the thin edge of the wedge, domino fallacy (as a form of domino effect argument) or dam burst, and various other terms that are sometimes considered distinct argument types or reasoning flaws, such as the camel's nose in the tent, parade of horribles, boiling frog, and snowball effect.

Some writers point out that strict necessity isn't required and it can still be characterized as a slippery slope if at each stage the next step is plausible.

[5] Some writers point out that an argument with the same structure might be used in a positive way in which someone is encouraged to take the first step because it leads to a desirable conclusion.

"[16] Walton suggests Alfred Sidgwick should be credited as the first writer on informal logic to describe what would today be called a slippery slope argument.

[18]: 84 Frank Saliger notes that "in the German-speaking world the dramatic image of the dam burst seems to predominate, in English speaking circles talk is more of the slippery slope argument",[19]: 341  and that "in German writing dam burst and slippery slope arguments are treated as broadly synonymous.

"[19]: 343 In exploring the differences between the two metaphors, he comments that in the dam burst the initial action is clearly in the foreground and there is a rapid movement towards the resulting events whereas in the slippery slope metaphor the downward slide has at least equal prominence to the initial action and it "conveys the impression of a slower 'step-by-step' process where the decision maker as participant slides inexorably downwards under the weight of its own successive (erroneous) decisions".

Walton argues that although the two are comparable "the metaphor of the dam bursting carries with it no essential element of a sequence of steps from an initial action through a gray zone with its accompanying loss of control eventuated in the ultimate outcome of the ruinous disaster.

"Bruce Waller says it is lawyers who often call it the "parade of horribles" argument while politicians seem to favor "the camel's nose is in the tent".

[21]: 252 The 1985 best-selling children's book If You Give a Mouse a Cookie by Laura Joffe Numeroff and Felicia Bond popularized the general idea of the slippery slope for recent generations.

"[24]: 1030 Those who hold that slippery slopes are causal generally give a simple definition, provide some appropriate examples and perhaps add some discussion as to the difficulty of determining whether the argument is reasonable or fallacious.

Lode, having claimed that SSAs are not a single class of arguments whose members all share the same form, nevertheless goes on to suggest the following common features.

The idea is that as soon as the agent in question takes the first step he will be impelled forward through the sequence, losing control so that in the end he will reach the catastrophic outcome.

Black and white cartoon of a tall woman in a tailcoat and knee-length skirt, and a short man delicately holding a bouquet. They stand together in front of a robed female reverend, about to be married. Behind the couple are two similarly attired same-sex pairs.
This 1895 cartoon makes a slippery-slope argument of how weddings would look in 2001 if women got the right to vote .