On Logical Fallacies

The following was a homework assignment for my Critical Thinking and Ethics course. I figured its content merits a post of its own, so I hope you find it informative. I learned quite a bit while writing it. 

A fallacy is an error in reasoning that violates at least one principle of good argumentation (as they were outlined in the previous homework). Despite the negative connotation, a fallacy isn’t necessarily malicious or intentional, but merely represents poor logic and argumentation on the part of its perpetrator. A single fallacy can undermine the legitimacy of an entire argument.

Because all humans are liable to think and argue poorly, even if we don’t mean to, we’re all susceptible to fallacious ways of thinking. Therefore, we should be alert to these fallacies not only to ensure the truthfulness of the arguments we encounter, but to help us from committing similar errors in reasoning. The following are just four of the fallacies typically encountered in various debates, although by no means the only ones.

Straw Man Fallacy
This is perhaps one of the most common fallacies, especially in the realm of politics. It consists of someone claiming to have successfully refuted an argument, when instead, they’ve attacked a weak or degraded version of it, e.g. the straw man. Often times, this corrupted argument seems similar enough (superficially at least) for a third party to buy into it. A straw man may be a deliberate attempt to make the opponent’s argument look bad (especially if an audience is involved), or may be the result of genuinely misinterpreting the argument.

For example, Alvin is arguing that the United States should grant some sort of amnesty to illegal aliens through a long-term process that includes background checks and citizenship tests. Bob counter-argues that Alvinwants to open the floodgates to millions of people who will take American jobs.

Instead of challenging Alvin’s argument on its merits or rationale, Bob “attacked a straw man” by claiming that his opponent wants America to be taken over by foreigners. Obviously, Alvin said no such thing, but Bob is distorting his statement while also making him seem like an awful person. Not only does doing this undermine what could otherwise be a worthy discussion, but assuming it was intentional, what Bob is doing is dishonest and unethical, thereby violating the principle of charity for any rational discussion.

Irrelevant or Questionable Authority
Behind most good arguments are good sources: studies, institutions, specialists, or other authorities that help add weight and legitimacy to one’s point. Even the most educated person doesn’t know everything, which makes reliance on experts a necessity. However, not every authority is credible, and this fallacy entails relying on a source that either has no bearing on the argument for which it is used, or that is illegitimate due to bias or lack of credentials.

Annabel: I’ve decided I’m going to keep smoking, since it turns out it is safe.

Beatriz: Really? Says who?

Annabel: This study done by a group called Marlboro [a cigarette company].

Annabel believes smoking is okay for her health based on the research of a company that profits from people who smoke. Clearly, her argument is undermined by the fact that her source would have good reason to be biased in favor of smoking cigarettes – it is a questionable authority. She’d be committing the same fallacy if she relied on the opinion of a veterinarian or her Aunt Sally, both of whom would lack the credentials or relevant expertise on the matter being argued. Had Annabel cited research from the National Institute of Health or a specialist on respiratory health, her argument would be far less suspect. Always pay attention the authority your opponent is relying on, while being certain of the legitimacy of your own sources.

Post Hoc Fallacy
This error consists of confusing correlation with causation, whereby you claim that one event was caused by another event just because they occurred in chronological order. It’s a very easy mistake to make, since humans naturally seek out a pattern or relationship between certain factors in order to explain something, especially if those events follow in some kind of sequence.

For example, a landlord receives a new tenant in his apartment block. Shortly after, the water heater breaks down. The landlord insists that it must have something to do with the new occupant, since this happened not long after he moved in.

The landlord is committing a post hoc fallacy because he attributes one event (the water heater breaking) to another event (the new tenant moving in) on the sole basis that the former occurred after the latter. The fact that events occur in some temporal order tells us nothing about whether there is a relationship between them – it could simply be a coincidence. Now, it could very well be that the new renter is somehow responsible for breaking the water heater, but the landlord would need more evidence besides the order of events.

Hasty Generalization
This is arguably one of the most ubiquitous fallacies around. It consists of drawing a broad conclusion about something or someone based on a small sample size of data. Most people do this quite regularly: stereotyping, which occurs in nearly every society, consists of generalizing about a large and diverse group of people based on a few encounters.

For example: “People from Kansas are just awful. I just dealt with a tour group from there, and they were very rude and obnoxious.”

Kansas is a state of a nearly three million residents, so concluding that all of them are nasty people based on a handful of individuals is highly erroneous: a few people can’t possibly offer an accurate representation of an entire state. This is an easy trap to fall into because immediate anecdotal evidence often has a greater impact on us than an often long-term compilation of more data, studies, or statistics. Withhold reaching a conclusion about something until you’ve gathered more information or observed a larger sample size. Make sure arguments making broad claims are doing so based on sufficient data, especially if the argument is citing polls, surveys, or personal anecdotes.

Learn about other fallacies here. Familiarize yourself with these so that you may think and argue well and avoid being fooled or unjustly undermined in debates.

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