Category
Informal fallacies
An informal fallacy is an argument that fails for reasons you can’t see from its shape alone. The flaw is in the content: the reasons offered don’t bear on the conclusion, an assumption is doing work it hasn’t earned, or a word quietly changes meaning halfway through.
Unlike formal fallacies, most informal fallacies depend on context. Questioning someone’s reliability is a fallacy when it replaces a response to their argument, and entirely reasonable when you’re being asked to take their word for something. That’s why every entry here has a section on when it isn’t an error.
Entries (60)
- AmphibolyDrawing a conclusion from the wrong reading of a sentence whose grammar allows more than one meaning.
- Appeal to authorityAccepting a claim because someone presented as an authority said so, when their say-so isn’t good evidence on that question.
- Appeal to consequencesDeciding whether a claim is true by how good or bad it would be if it were true.
- Appeal to emotionTrying to win agreement by stirring up a feeling, such as pity, fear or outrage, in place of reasons that bear on the claim.
- Appeal to forceUsing a threat to get someone to accept a claim or stop disputing it, as if the threat were a reason to think the claim is true.
- Appeal to natureTreating “natural” as if it meant good, safe or right, and “unnatural” as if it meant bad.
- Appeal to noveltyTreating something as better or truer simply because it’s new.
- Appeal to popularityTreating the fact that many people believe or do something as proof that it’s true or right.
- Appeal to povertyTreating someone’s poverty or humble way of life as a reason to think they’re honest or right.
- Appeal to traditionTreating a belief or practice as right because it’s old, or because it has always been done that way.
- Appeal to wealthTreating someone’s wealth or financial success as a reason to think they’re right.
- Argument from fallacyConcluding that a claim is false because an argument for it was fallacious or badly made.
- Argument from ignoranceTreating a lack of proof as proof of the opposite, as in “it hasn’t been disproven, so it’s true” or “it hasn’t been proven, so it’s false”.
- Argument from personal incredulityConcluding that something is false, or impossible, because you can’t imagine or understand how it could be true.
- Begging the questionSupporting a claim with premises that already assume it, so the argument gives a doubter no independent reason to accept it.
- Chronological snobberyDismissing an idea because it’s old or from an earlier era, instead of asking whether it was ever shown to be wrong.
- Continuum fallacyConcluding that there’s no real difference between two things because they shade into each other with no sharp dividing line.
- Cum hoc ergo propter hocConcluding that one thing causes another only because the two occur together.
- EquivocationUsing one word or phrase in two different senses within an argument, so the conclusion seems to follow when it doesn’t.
- Etymological fallacyClaiming that a word’s “real” meaning is its original or older meaning, and that the way people use it now is therefore wrong.
- Fallacy of compositionConcluding that a whole or group has a property because its parts or members each have it.
- Fallacy of divisionConcluding that each part or member of something has a property because the whole or the group has it.
- False dilemmaPresenting a few options, usually two, as the only possibilities when there are others, or when more than one could be true.
- Genetic fallacyJudging a claim true or false by where it came from instead of by the evidence for it.
- Ad hominemRejecting an argument by attacking the person who made it instead of their reasons.
- Guilt by associationRejecting a person or an idea because of a disliked person or group it’s connected to, instead of on its own merits.
- Poisoning the wellDiscrediting someone in advance, so that anything they say afterward is dismissed before it’s heard.
- Tu quoqueDismissing a claim or criticism because the person making it doesn’t act consistently with it.
- Ad hominemRejecting an argument by attacking the person who made it instead of their reasons.
- Gish gallopOverwhelming an opponent with more weak or false points than they can answer in the time available, so that whatever goes unanswered looks conceded.
- Hasty generalizationConcluding something about a whole group from cases that are too few, or too unlike the group, to support a claim that broad.
- Just asking questionsSuggesting a claim by asking whether it’s true, so the suggestion spreads without the speaker having to support it.
- Kafka trapTreating someone’s denial of an accusation as evidence that the accusation is true, so that nothing they say could clear them.
- Loaded questionAsking a question that takes for granted something not yet established, so that any direct answer seems to admit it.
- Middle ground fallacyConcluding that the truth must lie somewhere between two opposing positions simply because they are opposed.
- Moralistic fallacyConcluding that something is true because it ought to be, or false because it would be wrong or unfair if it were.
- Motte and baileyAdvancing a bold claim, retreating to a modest one when challenged, then going back to the bold claim once the challenge has passed.
- Moving the goalpostsDemanding more or different evidence once the evidence you asked for has been supplied, so the question never counts as settled.
- Naturalistic fallacyConcluding how things ought to be from facts about how they are, as if the facts alone settled the question.
- No true ScotsmanSaving a generalization about a group from a counterexample by redefining the group afterward, so the counterexample no longer counts.
- Oversimplified causeTreating one contributing factor as the whole explanation for an outcome that took several factors acting together.
- Persuasive definitionRedefining a word with strong positive or negative force so that it covers what you want praised or condemned, while keeping the force.
- Post hoc ergo propter hocConcluding that one thing caused another only because it happened first.
- Proof by repetitionRepeating a claim, often many times, in place of giving reasons or evidence for it.
- Quoting out of contextPresenting someone’s words without the surrounding context, so they appear to say something they didn’t mean.
- Red herringAnswering a claim by raising a different issue, as if discussing that settled the original question.
- ReificationTreating an abstraction, like “nature” or “the market”, as a real thing that wants, decides or acts, and reasoning from that.
- Relative privationDismissing a problem or complaint because something else is worse, as if a bigger problem made the smaller one unreal or not worth fixing.
- Semantic anachronismReading a word in an old text with the meaning it has today, when it meant something else at the time the text was written.
- Shifting the burden of proofAnswering a request to support your claim by demanding that the other person prove it false.
- Slippery slopeRejecting a first step because it will supposedly lead, one step after another, to disaster, without good reason to think each step will follow.
- Special pleadingHolding others to a rule or standard while exempting yourself or a favored case, without a relevant difference that justifies the exception.
- Straw manRefuting a distorted or weaker version of someone’s position instead of the position they actually hold.
- Suppressed evidencePresenting the evidence that supports a conclusion while leaving out known evidence that points the other way.
- Teleological fallacyExplaining a natural feature or process by the purpose it seems to serve, as if the benefit itself had brought it about.
- Texas sharpshooter fallacyTreating a pattern in data as meaningful when the boundaries that make it stand out were drawn after seeing where the data fell.
- Thought-terminating clichéEnding a question or a discussion with a stock phrase that sounds like an answer but gives no reason, such as “it is what it is”.
- Two wrongs make a rightDefending a wrong action by pointing to someone else’s wrongdoing, as if the other wrong made this one acceptable.
- Weak analogyConcluding that two things alike in some ways must be alike in another, when the similarities don’t bear on that way or a relevant difference undoes them.
The traditional groups
Informal fallacies are usually sorted into three broad families. The boundaries are loose and textbooks disagree about where some fallacies go.
- Relevance. The premises don’t actually bear on the conclusion. Attacking the arguer instead of the argument (Ad hominem) is the classic case.
- Presumption. The argument depends on an assumption that hasn’t been established, such as a false choice between two options or a conclusion smuggled into the premises.
- Ambiguity. A word or phrase is used in two senses, so the argument only seems to connect.
Naming it is not refuting it
Calling out an informal fallacy is a starting point, not a verdict. The useful follow-up is always the same question: does this flaw actually undermine the conclusion here? Treating “that’s a fallacy” as a winning move is its own reasoning error, and a common one.
Informal fallacies and biases
An informal fallacy belongs to an argument. A Cognitive bias belongs to a person’s judgment. They often travel together: a bias makes a certain bad argument feel convincing, and that argument then gets written down.
Other categories: Formal fallacies · Cognitive biases · Research biases