What Is a Slippery Slope Fallacy?

A slippery slope fallacy is an argument in which someone presents a statement that one act or event must eventually lead to another, without proof to support this series of events. The exact nature of such an argument can consist of nothing more than the beginning and ending situations, with few intermediary events. More elaborate slippery slopes, however, often include numerous steps that are going to occur to create the transition from beginning to end, with no evidence to support the likelihood of these events. A slippery slope fallacy can also occur as a result of someone using two states that have a difference between them, which is hard to define, to argue that one state does not exist.

One of the most common ways in which this fallacy can occur is through the process of someone creating causality where none exists. This is often seen coming from political figures, who frequently create a slippery slope fallacy in their arguments. Someone arguing in favor of keeping a drug illegal, for example, might argue that “If we legalize this one drug, then we will legalize another, and another, until nothing is prohibited and society crumbles.” The problem with this argument, however, is that there is no proof that the first event will lead to the next, nor to the final result in the argument.

These different consequences are typically the best way for someone to attack the fallacy. The more links someone uses within such an argument, between the beginning event and the end, the easier it often is for someone to attack these links. An argument’s weakness can also be found in how well each of these links relate to each other and are relevant to the overall argument. Someone wishing to attack the fallacy should look at how many events are necessary to possibly move from the beginning to the end of the slope, and point out weak connections between each link.

A slippery slope fallacy can also be created in a second way, based on connections between two ideas. Someone can argue that because one thing is similar to another thing, in a way that is difficult to clearly define, then one of those two things does not truly exist. For example, the distinction between beneficial and harmful plants found in nature can be difficult to perfectly define without exception. Someone may construct a slippery slope fallacy based on this fact, by asserting that this weak distinction means that all plants found in nature can be harmful.