fallacy.wiki

A field guide to the ways reasoning breaks

The eleven clusters

All 91 fallacies on one sheet, grouped by what breaks. Made to print.

Attacks on the source

Judging the speaker instead of the argument

  • Ad hominemRejecting an argument by attacking the character or circumstances of the person making it.
  • Tu quoqueDismissing a claim because the speaker does not live up to it.
  • Genetic fallacyJudging a claim by where it came from rather than what it says.
  • Poisoning the wellDiscrediting a person in advance so that whatever they say is received as suspect.
  • Quoting out of contextRemoving words from their surroundings so they carry a meaning the speaker did not intend.
  • Guilt by associationRejecting a position because a disliked group also holds it.
  • Reductio ad HitlerumTreating a view as refuted because a notorious figure or regime shared it.
  • Ad lapidemDeclaring a claim absurd without giving any reason why.

Broken structure

The form itself does not carry the conclusion

  • Affirming the consequentFrom if A then B, and B is true, wrongly concluding A. Other causes of B are ignored.
  • Denying the antecedentFrom if A then B, and A is false, wrongly concluding B is false. A may not be the only route to B.
  • Circular reasoningAssuming in the premises the very thing the argument is supposed to establish.
  • EquivocationUsing one word in two different senses within the same argument.
  • Definist fallacyDefining a contested term in a way that settles the dispute by wording alone.
  • ReificationTreating an abstraction as if it were a concrete agent that can act or want.
  • Undistributed middleConcluding that two things are the same because they share one property.
  • Illicit majorDrawing a conclusion about all of a category from a premise that covered only part of it.
  • Fallacy of four termsA syllogism that looks valid but uses four terms because one word shifted meaning.
  • Existential fallacyConcluding that something exists from premises that only describe a category conditionally.
  • Affirming a disjunctAssuming that because one option in an or statement is true, the other must be false.
  • Masked man fallacySubstituting identical things inside a statement about belief or knowledge, where it does not hold.
  • AmphibolyDrawing a conclusion from a sentence whose grammar allows more than one reading.
  • Fallacy of accentChanging the meaning of a statement by where the stress or emphasis falls.

False choices and ranges

Options and spectrums squeezed out of shape

  • False dilemmaPresenting two options as the only ones when more exist.
  • Slippery slopeClaiming one small step must lead to an extreme outcome, without defending the links.
  • Middle groundAssuming the truth must lie halfway between two positions.
  • Continuum fallacyDenying a real distinction because no exact boundary can be drawn between its ends.
  • Nirvana fallacyRejecting a workable option because it falls short of an ideal that is not available.

Part and whole

Traits smuggled between members and groups

  • Fallacy of compositionInferring that what is true of the parts must be true of the whole they form.
  • Fallacy of divisionInferring that what is true of the whole must be true of each of its parts.
  • Ecological fallacyDrawing a conclusion about an individual from statistics about the group they belong to.
  • Fallacy of accidentApplying a general rule to a case that its rationale was never meant to cover.

Crowds and prestige

Numbers, custom and status standing in for reasons

  • Argumentum ad populumTreating the number of people who hold a belief as evidence that the belief is true.
  • Appeal to common practiceJustifying an action because it is widely done, rather than because it is right.
  • Appeal to traditionHolding that something is correct or best because it is long established.
  • Appeal to noveltyHolding that something is better simply because it is newer.
  • Snob appealTreating association with an elite or admired group as evidence of quality.
  • Appeal to authorityCiting an authority as proof when the authority is outside their field, is not a consensus, or gives no reasons.
  • False attributionSupporting a claim with a source that is irrelevant, unqualified, unnamed, or invented.
  • Argumentum ad nauseamTreating repetition as if it were support, so a claim gains credibility by being said often.

Distraction and distortion

Moving the argument somewhere easier to win

  • Straw manReplacing an opponent's position with a weaker version and refuting that instead.
  • Red herringIntroducing a side issue that draws attention away from the question at hand.
  • Loaded questionAsking a question that smuggles in an unproven assumption, so any direct answer concedes it.
  • Gish gallopBurying the other side under many weak claims at once so none can be answered properly.
  • Kettle logicPiling up defences that contradict each other, each undermining the others.
  • Motte and baileyAdvancing a strong controversial claim, then retreating to a modest one when challenged.
  • Moving the goalpostsDemanding new evidence once the original demand has been met.
  • Special pleadingClaiming an exemption from a rule without giving a principled reason for the exemption.
  • WhataboutismAnswering a criticism by pointing at someone else's failing instead of addressing it.
  • False equivalenceTreating two cases as comparable when they differ enormously in scale or kind.
  • Style over substanceLetting the polish of a presentation stand in for the quality of its content.
  • Ad hoc rescueAdding an unsupported excuse after the fact to save a claim that failed.
  • UnfalsifiabilityFraming a claim so that no possible observation could count against it.

Causal errors

Sequence, coincidence and hindsight read as cause

  • Post hoc ergo propter hocTreating sequence as causation, so whatever came first is taken to have caused what followed.
  • Correlation implies causationReading a statistical association as proof that one variable drives the other.
  • Regression fallacyCrediting an intervention for an improvement that was a return to normal after an extreme.
  • Gambler's fallacyBelieving that independent events correct themselves, so a run makes the opposite due.
  • Fallacy of the single causeReducing an outcome with many contributing causes to just one.
  • Hindsight biasTreating an outcome as having been obvious once you know it happened.
  • Historian's fallacyJudging past decisions by information that only became available later.

Emotional pressure

Feeling recruited to do the work of evidence

  • Appeal to emotionUsing feeling as the main support for a conclusion instead of reasons.
  • Appeal to fearDriving acceptance by raising alarm rather than by showing the claim is true.
  • Appeal to pitySubstituting sympathy for the person in place of support for the claim.
  • Appeal to forceReplacing an argument with a threat of harm or loss.
  • Appeal to flatteryUsing praise to secure agreement rather than giving reasons.
  • Appeal to spiteExploiting resentment toward someone as a reason to reject their position.
  • Wishful thinkingBelieving something because the alternative is unbearable.
  • Appeal to consequencesJudging a claim true or false by whether its implications are pleasant.

Evidence and sampling

The data that was gathered, and the data that was not

  • Hasty generalizationGeneralizing from a sample too small or too narrow to support the conclusion.
  • Anecdotal evidencePreferring a vivid personal story over systematic data.
  • Cherry pickingPresenting only the data that supports a position while leaving out the rest.
  • Survivorship biasStudying only the cases that made it through, so the failures never enter the sample.
  • Texas sharpshooterDrawing the target around the hits, so a pattern is defined after the data is seen.
  • Base rate neglectReading a test result or signal without accounting for how rare the underlying condition is.
  • Conjunction fallacyJudging a detailed, specific scenario as more likely than the broader one that contains it.
  • Argument from silenceTreating the absence of a record as proof that the event did not occur.
  • Slothful inductionRefusing the conclusion that a strong body of evidence points to.

Burden and ignorance

Not knowing treated as knowing

  • Appeal to ignoranceTaking the lack of disproof as proof, or the lack of proof as disproof.
  • Shifting the burden of proofRequiring the other side to disprove a claim that was asserted without support.
  • Argument from incredulityConcluding that something is false because you cannot imagine how it could be true.

Values and premises

Hidden value claims doing the arguing

  • Is-ought fallacyDeriving a claim about what should be from a claim about what is.
  • Appeal to natureTreating natural as a synonym for good, safe, or right.
  • No true ScotsmanRedefining a category mid-argument to exclude any counterexample.
  • False analogyTransferring a conclusion between two cases that differ in the respect that matters.
  • Sunk cost fallacyLetting money or effort already spent justify continuing, when only future returns matter.
  • Fallacy fallacyConcluding a claim is false because the argument given for it was flawed.
  • Moralistic fallacyConcluding that something is not the case because it ought not to be.
  • Just-world fallacyAssuming outcomes are deserved, so misfortune implies fault.
  • Two wrongs make a rightJustifying a wrong by pointing to a comparable wrong done by someone else.
  • Etymological fallacyInsisting a word's original meaning is its correct meaning today.
  • Chronological snobberyRejecting an idea because it belongs to an earlier era.
  • Package deal fallacyTreating separable positions as a bundle that must be accepted or rejected together.