Fallacies

Why is it important to call out fallacies in an argument? A fallacy is a flaw in reasoning that renders an argument invalid, unsound, or weak, even if the conclusion happens to be true. Fallacies occur when the premises do not logically support the conclusion, either because of faulty structure (formal fallacies, such as affirming the consequent or denying the antecedent) or because of irrelevant, misleading, manipulative, or insufficient content (informal fallacies, such as ad hominem attacks, straw man distortions, slippery slopes, appeals to emotion, or begging the question). In essence, a fallacy is a breakdown in the chain of logic that connects evidence or reasons to the claim being made.

Identifying and calling out fallacies in a debate is important because it keeps the discussion focused on substance rather than rhetorical tricks, emotional manipulation, or distraction. When fallacies go unchallenged, they can make bad arguments appear persuasive, mislead audiences, waste time on irrelevant tangents, or create the illusion of victory without actually addressing the real issue. By naming and explaining the fallacy, a participant forces the conversation back to evidence, clarity, and sound reasoning. This promotes intellectual honesty, helps everyone (including observers) evaluate claims more critically, and raises the overall quality of discourse. Ultimately, exposing fallacies is one of the most effective ways to defend truth-seeking over mere persuasion or point-scoring.

Types of Fallacy

Formal Fallacy

Definition: These are errors in the logical structure (syntax/form) of the argument. The argument is invalid because the conclusion does not logically follow from the premises, regardless of what the words actually mean. You can spot them purely by looking at the abstract pattern or symbolic form of the reasoning — no need to understand the specific content or real-world meaning.

How to spot them: Translate the argument into symbolic logic (e.g., using propositional or categorical logic). If the form is invalid, it's a formal fallacy. The argument would remain invalid even if you replaced the terms with meaningless symbols.

Common examples: Affirming the consequent: If P then Q. Q. Therefore P. Example: "If it rains, the ground is wet. The ground is wet. Therefore, it rained." (Could be from sprinklers — invalid form.) Denying the antecedent: If P then Q. Not P. Therefore not Q. Example: "If you study, you pass. You didn't study. Therefore, you won't pass." (You might pass anyway for other reasons — invalid form.)

Key point: Formal fallacies make the argument deductively invalid. Even if the premises are true, the conclusion could still be false.

Informal Fallacy

Definition: These are errors in the content, context, language, relevance, or assumptions of the argument — not in its abstract logical form. The structure might be perfectly valid (or non-deductive), but the reasoning is flawed because of what is said, irrelevant information, emotional manipulation, ambiguity, or faulty assumptions. How to spot them: You need to understand the meaning of the words, the real-world context, background knowledge, or whether premises are relevant/justified. You can't detect them just from symbolic form — they require examining semantics, pragmatics, or evidence.

Common examples: Ad Hominem: Attacking the person instead of the argument. Example: "You can't trust his climate data — he's a liberal." Straw Man: Misrepresenting the opponent's position to attack a weaker version. Appeal to Authority: "This must be true because an expert said so" (without relevant expertise or evidence).

Key point: Informal fallacies can appear in valid deductive arguments or in inductive/everyday reasoning. They often make the argument weak, irrelevant, or unpersuasive even if the form isn't broken. They are far more common in real-life debates, politics, advertising, and media.

Logical Fallacies – Sorted Alphabetically by Name

Here is a list of around 70 fallacies. There may be others, if you want one added to the list let us know!

Fallacy Name	Type	Description (How to Spot It)	Example
Ad Hominem	Informal	Attacking the arguer's character/motives instead of the argument. Spot when response targets person, not reasoning.	'You can't trust his climate data — he's a liberal activist.'
Affirming the Consequent	Formal	If P then Q. Q. Therefore P. Spot invalid conditional reversal.	'If rain, streets wet. Streets wet. So rained.' (could be sprinklers)
Appeal to Authority	Informal	Claiming true because 'expert' says so, without evidence/relevance. Spot 'because X says' replacing proof, especially irrelevant authority.	'This supplement works — a celebrity doctor promotes it.'
Appeal to Consequences	Informal	Arguing true/false based on desirable/undesirable outcome. Spot wishful thinking via results.	'If evolution true, life meaningless — so false.'
Appeal to Emotion	Informal	Using feelings (pity/fear/anger) instead of logic. Spot emotional manipulation substituting for evidence.	'Support this policy — think of the suffering children if you don't!'
Appeal to Ignorance	Informal	Claiming true because unproven false (or vice versa). Spot absence of evidence as evidence.	'No proof aliens don't visit, so they do.'
Appeal to Nature	Informal	Claiming good because 'natural' or bad because 'unnatural'. Spot assuming natural=good without reason.	'GMOs are bad because unnatural, unlike natural crops.'
Appeal to Novelty	Informal	Claiming better because new. Spot 'latest' = superior without evidence.	'This new theory is modern, so better than old ones.'
Appeal to Pity	Informal	Evoking sympathy instead of evidence. Spot pity replacing logic.	'Don't fail me — my family depends on this degree.'
Appeal to Tradition	Informal	Claiming right because old/traditional. Spot age alone as justification.	'We've always done it this way, so continue.'
Argument from Incredulity	Informal	Claiming false because can't understand/believe. Spot 'I can't imagine how' as disproof.	'I can't see how life arose naturally, so God did it.'
Bandwagon (Appeal to Popularity)	Informal	Arguing true/good because many believe/do it. Spot 'everyone knows/does' as proof.	'Billions use this app, so it must be the best.'
Base Rate Fallacy	Informal	Ignoring prior probabilities in favor of conditional. Spot neglecting base rates in judgment.	'Test 99% accurate for rare disease. Positive — must have it.' (ignores low prevalence)
Begging the Question	Informal	Using conclusion as premise/assumption. Spot restating claim instead of supporting.	'The Bible is true because it's God's word, and God wrote the Bible.'
Burden of Proof Shift	Informal	Demanding opponent disprove claim instead of proving it. Spot 'prove it isn't' as proof.	'Prove God doesn't exist — if not, He does.'
Circular Reasoning	Informal	Using conclusion as premise/assumption. Spot restating claim instead of supporting.	'The Bible is true because it's God's word, and God wrote the Bible.'
Composition Fallacy	Informal	Assuming true of parts = true of whole. Spot part-to-whole error.	'Each atom is invisible, so the table is invisible.'
Conjunction Fallacy	Informal	Assuming specific conjunction more probable than single condition. Spot detailed story seeming likelier.	'Linda bank teller more likely than just bank teller.'
Continuum Fallacy (Sorites)	Informal	Denying distinction because no sharp cutoff. Spot 'where's the line?' denying categories.	'No exact point someone becomes bald, so no one is bald.'
Denying the Antecedent	Formal	If P then Q. Not P. Therefore not Q. Spot invalid negation.	'If study, pass. Didn't study. Won't pass.' (could pass anyway)
Division Fallacy	Informal	Assuming true of whole = true of parts. Spot whole-to-part error.	'The team is great, so every player is great.'
Ecological Fallacy	Informal	Inferring individual from group data. Spot group stats wrongly to person.	'Country has high IQ average, so you must be smart.'
Equivocation	Informal	Shifting word meaning mid-argument. Spot ambiguity creating false logic.	'Banks are riversides. Money is in banks. Money is riverside.'
Existential Fallacy	Formal	Universal premises to particular conclusion without existential import. Spot assuming existence wrongly.	'All unicorns have horns. So some unicorns have horns.'
Fallacy Fallacy	Formal	Assuming that because an argument has a fallacy, the conclusion must be false. Spot dismissing claim solely because reasoning is flawed.	'You used a straw man, therefore your position is wrong.'
False Cause	Informal	Wrongly attributing cause. Spot weak/coincidental link as causation.	'New policy started, economy improved — policy caused it.'
False Dilemma (Black-and-White)	Informal	Presenting only two extremes when more options exist. Spot forced binary ignoring nuance/middle ground.	'You're either for freedom or for terrorism.'
Gambler's Fallacy	Informal	Believing past independent events affect future. Spot 'due' after streak.	'Coin landed heads 10 times — tails next for sure.'
Genetic Fallacy	Informal	Judging claim by origin/source, not merits. Spot dismissing/supporting based on source alone.	'That idea came from a biased outlet, so false.'
Hasty Generalization	Informal	Broad conclusion from small/unrepresentative sample. Spot 'some' treated as 'all/most'.	'Two bad experiences with that airline — they're all terrible.'
Illicit Major	Formal	Major term undistributed in premise but distributed in conclusion. Spot invalid syllogism.	'All A are B. No C are A. So no C are B.' (invalid distribution)
Loaded Question	Informal	Question assuming disputed premise. Spot built-in controversial assumption.	'Have you stopped cheating on taxes?'
Ludic Fallacy	Informal	Misapplying game-like probabilities to real unpredictable events. Spot ignoring real-world chaos.	'Model predicts market perfectly like dice game.'
Masked Man Fallacy	Formal	Substituting identicals fails in intensional contexts. Spot opacity error.	'I know Clark Kent. Clark Kent is Superman. So I know Superman.' (may not)
Moving the Goalposts	Informal	Changing criteria after evidence provided. Spot raising requirements post-hoc.	'Show one example. Ok, now show ten.'
Nirvana Fallacy	Informal	Rejecting good solution because not perfect. Spot 'not 100%' dismisses viable option.	'Vaccines don't prevent all cases, so useless.'
No True Scotsman	Informal	Redefining group to exclude counterexamples. Spot moving goalposts on definition.	'No true patriot criticizes the country.'
Poisoning the Well	Informal	Preemptively discrediting source. Spot attacking credibility before argument.	'Don't listen to him — he's biased before he speaks.'
Post Hoc Ergo Propter Hoc	Informal	Assuming A caused B just because A preceded B. Spot sequence alone as causation proof.	'I prayed, then it rained — prayer caused rain.'
Red Herring	Informal	Introducing irrelevant topic to distract. Spot subject change away from issue.	'Why focus on pollution when jobs are more important?'
Reification	Informal	Treating abstract as concrete. Spot idea as physical entity.	'Society demands obedience.'
Slippery Slope	Informal	Claiming small step inevitably causes extreme outcome without evidence. Spot unproven chain of doom.	'Legalizing marijuana leads to legalizing heroin and societal collapse.'
Special Pleading	Informal	Double standards without justification. Spot exempting self/group unfairly.	'Rules apply to everyone else, but my case is special.'
Straw Man	Informal	Misrepresenting/exaggerating opponent's position to attack easier version. Spot distorted or weakened claim being refuted.	'She wants gun regulations, so she wants to ban all guns and disarm citizens.'
Sunk Cost Fallacy	Informal	Continuing due to past investment, ignoring future benefit. Spot 'I've invested too much to quit'.	'This project failed so far, but I've spent millions — keep going.'
Texas Sharpshooter (Cherry Picking)	Informal	Selecting data fitting conclusion, ignoring rest. Spot post-hoc bullseye or selective highlighting.	'My stock picks succeeded — look at these winners!' (hiding losses)
Tu Quoque (You Too)	Informal	Dismissing criticism because critic does similar. Spot 'but you do it too' evading issue.	'You criticize speeding, but you've sped before.'
Undistributed Middle	Formal	Syllogism where middle term not distributed. Spot invalid categorical link.	'All dogs mammals. All cats mammals. So all dogs cats.'