Logical Fallacies

Logical fallacies are incorrect ways to make a point. They are “common errors in reasoning that will undermine the logic of your argument.” We’re going to list some of the most common logical fallacies that students often use to incorrectly make their points.

Tip: Many times, logical fallacies are used as a crutch for an already weak argument. If you find yourself falling into any of these, it may mean you need to do some more research to find better support for your argument.

Slippery Slope

You will often hear the slippery slope argument when listening to politicians. It is an argument that says, “If this happens, then through a series of small steps, this other thing will happen.” If A, then B, C...X, Y, Z will happen too. Therefore if A, then Z.

For example, “If hummers are banned because of environmental reasons, then all cars will eventually be banned.”

This line of thinking is flawed because each step does not necessitate the next. Hummers may be banned, but Priuses may not be. There is an opportunity at each step for something completely different to occur.

Hasty Generalization

This fallacy is about jumping to a conclusion before yo have sufficient evidence to support your claim. It is a kind of summation of an entire object because of one instance.

For example, “Even though I’ve only had one pizza, I know that pizza is the best food ever.” Pizza may very well be the “best food ever,” but we cannot come to that conclusion based on the limited evidence we have. Another example, “It is cold today, so the entire year is going to be cold.”

Post Hoc Ergo Propter Hoc

In Latin, this means “after this, therefore resulting from it.” It is a way of saying that if B comes after A, then A must have caused B. Just because something occurred after something else, does not mean that the two are related.

For example, “I ate an apple and then got sick. The apple must have made me sick.” We may be able to build an argument the the apple was bad and did cause you to become ill, but with this information, we cannot logically come to this conclusion.

Genetic Fallacy

This is a method for devaluing an argument, person, theory, etc. based on its origins. Just because something has questionable origins, does not mean that it is bad. The quality of somethings origins does not necessarily define it. Each idea or object must be judged upon its own merit.

For example, “The Volkswagen Beetle must be evil because it was designed by Hitler’s military.” Another example, “Einstein was a horrible person, so his theory of relativity must be wrong.”

Begging the Claim

Students will often use this fallacy when trying to make a strong argument. However, it only undermines it. It is a

way of constructing an argument or sentence so that the conclusion is already assumed at the beginning.

For example, “Filthy and polluting coal should be banned.” The conclusion that coal should be banned should be made separately from the conclusion that it is filthy and polluting. Begging the claim is about assuming other claims to make another. Each claim must be made independently.

Circular Argument

This is an argument that uses itself as its proof.

For example, “I am happy because I am elated.” In this sentence, “happy” and “elated” are effectively the same thing. If I want to prove that I am happy, I must bring new evidence to my argument. I need specific evidence such as I heard a funny joke, I am surrounded by friends, or that I enjoy my work to support that I am either happy or elated. Arguments must provide evidence distinct from their conclusions.

Either/Or

Either/Or fallacies over simplify situations to the point that they offer a false dichotomy. This is another argument that is common to political discourse.

For example, “We either stop driving cars or destroy the earth.” These are not the only options when it comes to being better stewards of the planet. We could drive cars that use less fuel are powered by renewable energy or discover new technology to counter their polluting effects.

Ad Hominem

These are attempts to undermine an argument by attaching the character of a person/author rather than her/his ideas.

For example, “My doctor’s diagnosis is wrong because he is a jerk.” While your doctor may be a jerk, that doesn’t mean that his diagnosis is wrong.

Another example, “I’m not going to listen to my doctor advice to quit smoking because she smokes.” Just because your doctor doesn’t follow her own advice doesn’t disqualify the advice that smoking is harmful to your health.

Ad Populum

Ad populum fallacies attempt to make emotional appeals instead of supporting an argument. They attempt to use broad concepts (such as patriotism, terrorism, democracy, etc.) instead of addressing the real issue at hand.

For example, “True Americans support the rights of people to choose whatever vehicle they want.” In this example, the author uses a popularly desired feeling (being a “true American”) to support the argument even though there is no inherent connection between the two. There are/could be Americans who believe that not all cars should be available for purchase. Instead, the author should rely on ideas such as constitutionality and legal rights to make their argument.

Red Herring

This is an attempt to distract from the main argument by raising another.

For example, “Mercury levels in seafood may be unsafe, but what else will fishers do to support their families?” The author changes the topic from the safety of seafood to the economics of fishers. While these two issues may be related, it does not preclude either one from being addressed in a real way.

Straw Man

Straw man fallacies are attacks on another’s argument by oversimplifying it and then attacking the oversimplified version of the argument. This is a common mistake for new students or students who are in a hurry.

An example would be, “People who don’t support higher fuel standards hate the environment.” The author of this statement has assumed that it is a hatred for the environment that supports opposition to higher fuel standards. In reality, opponents may have various, legitimate, and complex reasons for not supporting higher fuel standards. By not engaging in the complexity of different positions, the author is undermining his/her own argument.