List of Logical Fallacies, With Examples

A logical fallacy is an error in reasoning (IEP). Below are 19 of the most common ones, each with a one-line definition and an everyday example, sorted into four families: relevance, weak induction, presumption and ambiguity. After the list you’ll find two common formal fallacies and some advice for when you spot one.

What a logical fallacy is

The Internet Encyclopedia of Philosophy calls a fallacy “a kind of error in reasoning.” Most fallacies involve arguments, though some involve explanations, definitions or questions (IEP). The traditional definition, as C. L. Hamblin summed it up in 1970, is an argument that “seems to be valid but is not so” (SEP). The Stanford Encyclopedia of Philosophy says this is often called the standard definition, though nearly all newer approaches to fallacies reject it (SEP).

Whatever the definition, fallacies do fool people. The UNC Writing Center says fallacious arguments are very common and can be quite persuasive to a casual reader or listener. It also treats arguments as a scale from very weak to very strong, so the useful question is how well the reasons support the claim (UNC Writing Center).

Formal vs. informal fallacies

A formal fallacy is wrong because of its logical form, whatever the argument is about (IEP). Irving Copi’s influential logic textbook lists affirming the consequent and denying the antecedent among them (SEP):

• Affirming the consequent: “If it rained, the street is wet. The street is wet. So it rained.” A sprinkler could have done it. The IEP notes this is often mistaken for a valid form called modus ponens (IEP).
• Denying the antecedent: “If it rained, the street is wet. It didn’t rain. So the street isn’t wet.” This one is often mistaken for modus tollens (IEP).

An informal fallacy depends on content instead: the reasons given don’t adequately support the conclusion (OpenStax). All 19 fallacies below are informal. For how valid and strong arguments work, see deductive vs. inductive reasoning.

How fallacies are grouped

The IEP says plainly that “the taxonomy of the fallacies is in dispute” (IEP). Aristotle split fallacies into those that depend on language and those that don’t, and Copi’s 1961 textbook divided informal fallacies into relevance and ambiguity (SEP). Two current open textbooks each use four groups, but different ones. OpenStax uses relevance, weak induction, unwarranted assumption and diversion (OpenStax). Matthew Knachel’s Fundamental Methods of Logic uses distraction (also called relevance), weak induction, illicit presumption and linguistic emphasis (Knachel).

This guide uses relevance, weak induction, presumption and ambiguity, and notes where a source files a fallacy somewhere else.

Fallacies of relevance

The reasons offered don’t bear on the conclusion, even if they seem to (OpenStax).

Fallacy	What it is	Everyday example
Ad hominem	Making an irrelevant attack on the person arguing and suggesting it undermines their argument (IEP)	“Why listen to his budget plan? He can’t even keep his desk tidy.”
Tu quoque (“you too”)	Rejecting someone’s argument because they don’t practice what they preach (IEP)	“You say I should stop eating fast food, but I saw you at a drive-through yesterday.”
Straw man	Setting up a weak version of the other side’s position and knocking that down instead (UNC)	“We should have fewer meetings.” “So you think nobody should ever talk to each other?”
Red herring	Going off on a side issue that distracts from what’s really at stake (UNC)	“Sure, the report was late, but look how hard the team has worked this year.”
Appeal to emotion	Accepting a claim only because the appeal stirs up feelings such as fear, pity or pride (IEP)	“Imagine how you’ll feel if something breaks and you skipped the extended warranty.”
Appeal to the people (bandwagon)	Claiming something is right because many people believe it (UNC, Purdue OWL)	“Everyone at work is on this diet, so it must work.”
Appeal to authority	Relying on someone who isn’t really an authority on the subject in question (IEP)	“My dentist says this stock will double, so I’m buying.”

The IEP says there’s nothing wrong with using emotions when you argue; the mistake is making them the key premise (IEP). A personal attack can also be relevant. In the IEP’s example, someone’s conduct says nothing about their views on astronomy but does matter if they’re up for a leadership role (IEP). Our guides to the ad hominem fallacy and the straw man fallacy go into both in more depth.

Sources disagree on a few of these. OpenStax puts straw man and red herring in a separate “diversion” group (OpenStax), while Knachel counts them as fallacies of distraction, his name for the relevance family (Knachel). Copi listed appeal to authority under relevance (SEP), but Knachel puts “appeal to inappropriate authority” under weak induction (Knachel).

Fallacies of weak induction

The reasons are relevant but too weak to establish the conclusion (OpenStax).

Fallacy	What it is	Everyday example
Hasty generalization	Drawing a general conclusion from too small a sample (IEP)	“Two drivers from that town cut me off, so everyone there drives badly.”
Post hoc (false cause)	Concluding that A caused B just because A came first (IEP)	“I wore my lucky socks and we won, so the socks helped.”
Slippery slope	Claiming a first step will lead, step by step, to a bad outcome, and exaggerating how likely that is (IEP)	“If we let her stay up late tonight, soon she’ll never sleep and her grades will collapse.”
Weak (false) analogy	Comparing things that are too different in the ways that matter (IEP, UNC)	“Picking a doctor is like picking a pizza place, so go with whoever has the best ads.”
Appeal to ignorance	Treating a lack of proof that something is true as proof that it’s false, or the reverse (IEP)	“No one has shown the new manager is honest, so she must be hiding something.”

Some of these have legitimate versions. Correlations are often good evidence of a causal link, so post hoc reasoning goes wrong only when the leap is made hastily (IEP). UNC notes that some chains of consequences really are predictable (UNC), and the IEP says a slippery slope argument is only as good as the probabilities at each step (IEP). Copi grouped appeal to ignorance with the relevance fallacies (SEP); OpenStax and Knachel both put it under weak induction (OpenStax, Knachel).

Fallacies of presumption

These arguments rest on a claim, often a hidden one, that’s assumed without good reason (Knachel).

Fallacy	What it is	Everyday example
Begging the question	Reaching a conclusion from premises that already assume it (IEP)	“This news site is trustworthy because it says it only reports the truth.”
False dilemma	Offering too few choices and implying you have to pick one of them (IEP)	“Either you work this weekend or you don’t care about the team.”
Loaded (complex) question	Wording a question so it builds in a controversial assumption (IEP)	“Have you stopped wasting money on takeout?”

Purdue OWL calls the false dilemma the “either/or” fallacy (Purdue OWL). Copi placed begging the question and complex question among the relevance fallacies (SEP).

Fallacies of ambiguity

These trade on words or sentences that can be read more than one way. Copi’s ambiguity group includes equivocation, amphiboly, composition and division (SEP).

Fallacy	What it is	Everyday example
Equivocation	Switching the meaning of a key word partway through the reasoning (IEP)	“The sign said ‘fine for parking here,’ so I figured parking was fine.”
Amphiboly	Reading a grammatically ambiguous phrase in two different ways (IEP)	“The flyer asks for volunteers to clean the park with dogs. I don’t have a dog, so I can’t help.”
Composition	Assuming that what’s true of a group’s members is true of the group as a whole (IEP)	“Every player on the team is an all-star, so the team will be great.”
Division	Assuming that what’s true of a group is true of each member (IEP)	“That company is rich, so everyone who works there must be rich.”

Knachel files composition and division under illicit presumption instead (Knachel).

How to respond when you spot a fallacy

Start by checking that it really is one. The IEP says the burden of proof is on you when you call someone’s reasoning fallacious, and a fallacy’s name can’t replace a close look at the passage and its context (IEP).

Then restate the other person’s argument. UNC’s advice is to be charitable and put their argument as strongly, accurately and sympathetically as you can (UNC). If they accept your summary, you know you’re arguing about the same thing.

Naming the fallacy out loud rarely helps much. Asking about the gap usually goes further: How does A lead to B? Are those really the only two options? Is that what she actually said?

Keep in mind that a bad argument doesn’t make its conclusion false. The IEP notes that truth can come out of bad reasoning (IEP), so the claim may still be right and just need better support.

The same checks work on your own reasoning. UNC suggests arguing against your own conclusion to find its weak spots, listing each claim with its evidence, learning which fallacies you tend to commit, and double-checking how you describe people you disagree with (UNC). There’s more on building that habit in how to improve your critical thinking.