For professor Geek

A Handy List of Fallacies

ad hominem A logical fallacy that attacks someone's character rather than addresses the issues.

Ex: “Of course Johnson’s plan doesn’t make sense. She’s an idiot.”

(The reason has nothing to do with the problems in Johnson’s plan. It instead talks about Johnson.)

bandwagon appeal A logical fallacy that argues for a thought or an action based on the sole defense that others support it.

Ex: “ Since 88% of the people polled believed in UFOs, they must exist.”

(Just because many people believe something does not make it true.) begging the question A logical fallacy that goes in a circle, assuming as a given what the writer is trying to prove.

Ex: Bill: "God must exist." Jill: "How do you know." Bill: "Because the Bible says so." Jill: "Why should I believe the Bible?" Bill: "Because the Bible was written by God."

(Similar to circular reasoning below. Bill’s final response here leads Jill back to her first question)

circular reasoning A fallacy in which the speaker’s claim also serves as her reason.

Ex. A dog is the best sort of pet because it is better than any other type of animal you could have as a pet.

(The claim here is simply restated. There is actually no reason supporting the claim that dogs make the best pets.)

either-or argument A logical fallacy that oversimplifies to suggest that only two possible positions exist on a complex issue. This fallacy is also known as a false dilemma.

Ex: Either rocks are alive or rocks are dead.

(The truth, that rocks are neither alive nor dead, is not accounted for.)

false analogy A fallacy comparing things that do resemble each other but that are not alike in the most important respects.

Ex: People are like dogs. They respond best to clear discipline.

(People do not wag their tails, or chase cats, shed the fur that covers them, etc... )

faulty causality A fallacy that mistakenly assumes the first of two events causes the second. This fallacy is also called post hoc, ergo propter hoc.

Ex: Bill bleached his hair blonde last week, and this week three other guys at the same school did the same; therefore the latter all changed their hair color because Bill did.

(There is no conclusive proof provided in these statements that indicate that the other boys did what they did because of Bill. This does not account for the any number of factors that might have resulted in their hair dying.)

hasty generalization A fallacy that reaches a conclusion based on insufficient or inappropriately qualified evidence.

Ex: Smith, who is from England, decides to attend graduate school at Ohio State University. He has never been to the US before. The day after he arrives, he is walking back from an orientation session and sees two white (albino) squirrels chasing each other around a tree. In his next letter home, he tells his family that American squirrels are white.

(Smith has not done any sort of research on this issue. He’s basing his opinion on his very limited observations.)

Non Sequitur A fallacy in which a reason is supposed to support a claim, but is in fact unrelated.

This category of informal fallacy is a "catch all" type. If a fallacy does not clearly fit into one of the common fallacies described above, it is to be identified as this fallacy.

Ex. I don’t deserve a B in this class because I am a straight A student.

(This person’s past performance is completely unrelated to her performance in the class at hand. Though often, we understand non sequiturs as being even more random/unrelated. Consider the following: “ I don’t deserve a B in this class because I have a watermelon.”)

red herring A fallacy referring to the practice of raising an irrelevant topic in order to detract from the issue at hand.

Ex. Sure, the candidate has a fabulous plan to end homelessness. But he also cheats on his wife.

(This non sequitur response clearly serves to maliciously deflect from the issue at hand. This is commonly used in political debates and discourse.)

slippery slope A fallacy that asserts, without evidence, that one event will lead to a series of other events that will culminate in a cataclysm.

Ex. "We have to stop the 2% tuition increase! The next thing you know, they'll be charging $40,000 a semester!"

(There is no evidence presented that suggests that raising tuition by 2% at the current time would lead to the next, “cataclysmic” number.)

A straw man argument is an informal fallacy based on misrepresentation of an opponent's position.

Tim: I don't think children should play on busy streets.

Tom: I think that it would be foolish to lock children up all day.

(Tom’s statement implies that Tim would have children locked up all day. But Tim never said anything of the sort.)