A slippery slope fallacy is a type of negative reasoning from consequences, in which there is a causal chain leading from the proposed action to a negative outcome. The fallacy depends on the premise that the proposed action will lead to the negative outcome through a series of causally connected actions. By connecting something causally to a negative outcome, it is hoped that it will be easier to discredit the thing. In other words, because we do not want the final, negative, event to occur, we should not do the first thing, because in doing so we would start a chain of events which will lead to the final negative outcome. The error in reasoning comes from the fact that the final outcome does not necessarily follow from the first.
Tindale, C. W. (2007). “”Correlation and Cause”. In Fallacies and Argument Appraisal “. Cambridge: Cambridge University Press. 185.