In this series of articles, we discuss common logical fallacies and try to inform the skeptical reader how to spot and avoid them. This time, we will take a closer look at The straw man [1] and the slippery slope [2] fallacies, which often appear in public (and private) debate. They are sometimes also used together to create a silly combination of illogical non-argumentation.

The straw man, as its name suggests, is a trick which consists in attempting to represent the opponent’s position in a weak and fragile way in order to more easily fight it. In other words, it is a misrepresentation of someone’s position made to imitate a frail scarecrow.

A real life example of straw-manning could be found in the typical anti-vaccine activists’ opinion that vaccines aren’t safe or that vaccines cause autism [3]. Typically, the debate revolves around using vaccines to prevent the spread of dangerous and highly infectious diseases (like COVID-19 or polio). Although vaccines, like many medicines, have side effects, the conclusion that vaccines are unsafe is a straw man, because the issue is more nuanced and using vaccines has more positive than negative effects. Changing the subject to alleged increased risk of autism is also an attempt to create an easier target. It is also false [4].

Carl Sagan, whom we mentioned in one of our previous articles, describes straw-manning as “caricaturing a position to make it easier to attack” and provides an anti-scientific quote stating that “scientists suppose that living things simply fell together by chance.” However, as Sagan points out, such formulation “willfully ignores the central Darwinian insight, that Nature ratchets up by saving what works and discarding what doesn’t” [5].

Moreover, it is worth keeping in mind that, in a debate, a straw man should be pointed out and refuted as quickly as possible. That is because if one gets lured into the fallacy trap, it may become increasingly difficult to argue against such a substitute subject chosen by the opponent [6].

Just like the straw man, the slippery slope is also a fallacy whose name is a metaphor. It means a situation which is getting progressively worse and may become catastrophic – presumably at the bottom of the slope. This fallacy also has other equally metaphorical names, including the dam burst argument, Pandora’s box argument, and the domino argument [7].

The fallacy consists in projecting the consequences of an action and blowing them out of proportion. For example, opponents of euthanasia sometimes use the slippery slope argument when they say that allowing euthanasia will lead to the killing of inconvenient elderly people. This argument is fallacious for at least two reasons. First of all, if action A leads to B, it doesn’t necessarily mean that B leads to C [7]. Secondly, there are numerous countries where euthanasia is legal and where the elderly aren’t murdered en masse; strict legal and medical criteria are applied [8].

Carl Sagan provides us with another example of the slippery slope. He cleverly uses the same type of fallacy to demonstrate how it can be applied by two sides of a political conflict. On the one hand, “if we allow abortion (…), it will be impossible to prevent the killing of a full-term infant.” On the other, “if the state prohibits abortion (…) it will soon be telling us what to do with our bodies at the time of conception” [5]. It is easy to see how such exaggerated misrepresentations may distort any debate about abortion.

As mentioned, the two fallacies can also appear together. This happens, for example, when someone argues that increasing social welfare leads to communism and then moves on to criticize communism. In this scenario, communism constitutes a slippery slope – because social welfare doesn’t lead to communism – and a straw man – because it’s easier to attack communism than to have a constructive debate about welfare initiatives. 

A skeptic should always be alert to logical fallacies, especially those abundant in political discourse. The straw man and the slippery slope are particularly dangerous because they are two of the most common fallacies and, unfortunately, they are often used in private arguments. Luckily, if pointed out quickly and confidently, they can certainly be avoided.