A fallacy is an error in reasoning. Think of a fallacy as a persuasive appeal that contains logical holes or poor use of evidence. We want to avoid fallacies when we speak to an audience, but fallacies are something we should also listen for when we are in the audience for a speech.

How, though, do we recognize bad arguments when we are confronted with them? Below you’ll find a list of common logical fallacies.

Fallacies in Reasoning

Hasty Generalizations

This one is so, so common. We are all likely guilty of forming hasty generalizations on a regular basis. When you make a hasty generalization, you make the error of jumping to a conclusion. A good generalization must meet two criteria:

• It must be made on the basis of a sufficient number of cases.
• And the cases must compose a representative sample of ALL cases.

Hasty generalizations occur when claims are not warranted, either because insufficient cases were used or because they constitute a non-representative sample.

Example: If we were to claim that “Phoenix is always snowy and cold” based on the evidence of two snowy days in January, we’d be guilty of 1) not basing our claim on a sufficient number of cases (as two days hardly qualifies as sufficient) and 2) not basing our claim on a representative sample of cases (to be representative we’d need to also sample days from November, February, etc.).

Transfer Fallacy

These fallacies extend reasoning beyond what is logically possible. Three types exist:

1. Fallacy of composition: when claims assert that what is true of a part is true of the whole.

   Examples: “Voters in Austin tend to be Democrats; therefore, voters in other counties in Texas must be Democratic as well.”

   “When you’ve seen one zoo, you’ve seen them all.”

2. Fallacy of division: when claims assert what is true of the whole is also true of its parts.

   Example: “Communication courses are fun, and Public Speaking is a communication course; therefore, Public Speaking is fun.” (We hope it is fun, but stated this way, the conclusion it is fun is a logical fallacy.)

3. Fallacy of refutation: (also known as the Straw Man Argument): when an arguer attempts to draw attention to the successful refutation of an argument that was never raised or restates a strong argument in a way that makes it appear weaker. Straw man arguments focus on issues that are easy to overturn. Such arguments are forms of deception because they introduce bogus claims, claims that were not part of the original argument, or they misrepresent the original claim.

   Example: “Your argument that drunk driving causes death and injury is very interesting, but what about all the people who weren’t wearing seat belts at the time of the accident? Aren’t you assuming every person involved in an automobile accident has been drinking? You can’t really make that claim until you look at some other information.”

Irrelevant Arguments

Also known as non sequiturs (Latin for “it does not necessarily follow”). Irrelevant arguments are ones that do not seem pertinent in terms of the claims they advance on the basis of proof they offer. They make assumptions that do not follow from the information provided.

Example: “Rolling Valley Vineyards must make great wines (claim). Their social media posts state that they are the only winery that doesn’t use pesticides to control insect damages to their vineyards. We should all be concerned about pesticides in what we eat and drink” (The proof does not follow from the claim).

Circular Reasoning

Also known as begging the question, arguments that are circular support claims with reasons identical to the claims themselves.

Example: “Everyone at school loves Michele because she is so popular. “

Avoiding the Issue

An error of reasoning that shifts attention from the issue under consideration. It commonly takes the form of:

• a simple evasion of the issue: changing the subject for no apparent reason.
• an attack on the arguer rather than the argument (an ad hominem attack).
• a shift of ground: when an arguer abandons their original position and adopts a new one.
• seizing on a trivial point rather than the central issue: when you magnify the weakest or most indefensible position of the other side all out of proportion to its actual importance.

Forcing a Dichotomy

A forced dichotomy is one in which audiences are presented with an oversimplified either-or choice, phrased in such a way that it forces them to favor the arguer’s preferred option.

Example: “We must censor video games because to not do so is to support the indefensible notion that video games do no damage to society when we know full well that they have major detrimental effects.”

Appeals to Ignorance

Known as ad ignoratium in Latin, these appeals ask the audience to accept the truth of a claim because no proof to the contrary exists. In other words, something is true because it cannot be proven false.

Example: “The inability to disprove the existence of flying saucers and extraterrestrial visitation to earth confirms the existence of the former and the occurrence of the latter.”

Appeal to the People

This is also known as the bandwagon appeal or, in Latin, the ad populum argument. When a claim is justified based only on its popularity, that is, we should believe the claim because the majority of people believe the claim, an appeal to the people is being made.

Examples: “Everyone is getting stars on their belly, so stars must be great and you should get one too!”

“Public opinion polls show that the majority of Americans favor congressional term limits; therefore, we ought to pass a constitutional amendment that limits the terms of members of Congress.”

Appeal to Authority

While an argument that uses the opinions and testimony of experts can be a legitimate form of reasoning, there are cases where such reasoning can be used carelessly and fallaciously. An appeal to authority is fallacious when it appeals to a seemingly authoritative source that lacks real expertise. Also, appeals to authority are fallacious when they encourage reliance on some ultimate source of knowledge in place of reasoning as the basis of a claim. Abuses of authority commonly involve religious texts such as the Bible, the Constitution, revered persons, or testimonials by celebrities in advertising.

Example: “I’m not a doctor but I play one on TV; therefore, you should use the brand of aspirin that I’m advertising.”

Appeal to Tradition

An appeal to tradition asks an audience to accept something just because it is customary rather than because there are reasons that justify it.

Example: “The Democratic party has always been the party of the environmental movement. Therefore it makes no sense for the Sierra Club to endorse a candidate who is not a Democrat.”