Post hoc, ergo propter hoc

	Cogito ergo sum; Logic and rhetoric
	Key articles
	Logical fallacy; Syllogism; Argument;
	General logic
	Argumentum ad nauseam; Galileo gambit; Science was wrong before; Didit fallacy; Rogerian argument; Envenenar o poço;
	Bad logic
	Selection bias; Cherry picking; Texas sharpshooter fallacy; Fallacy of accident; Argumentum ad lunam; Canard (português); v - t - e

An example observed in the wild

Post hoc, ergo propter hoc is a Latin phrase for "after this, therefore, because of this." The term refers to a logical fallacy that because two events occurred in succession, the former event caused the latter event.^[1]^[2]

In addressing a post hoc, ergo propter hoc argument, it is important to recognise that correlation does not equal causation.

Magical thinking is a form of post hoc, ergo propter hoc fallacy, in which superstitions are formed based on seeing patterns in a series of coincidences. For example, "these are my lucky trousers. Sometimes good things happen to me when I wear them."

Alternate names

Assuming the cause
Faulty Causal Assumption
Post hoc

Form of the argument

P1: X happened before Y.

P2: (unstated) Y was caused by something (that happened before Y).

C: Therefore, X caused Y.

Other examples

Many superstitions use this. For instance, a black cat crosses my path on the way to school. I then fail a test that day. If I used this fallacy, I may conclude I failed because of the black cat, while ignoring other factors such as the amount of time I spent studying.

The rooster crows before sunrise, therefore the crowing rooster causes the sun to rise.

The drunk scientist conducts an experiment to see why he gets hangovers. He decides to keep a diary. Monday night, scotch and soda; Tuesday morning, hangover. Tuesday night, gin and soda; Wednesday morning, hangover. Wednesday night, vodka and soda; Thursday morning, hangover. Thursday night, rum and soda; Friday morning, hangover. On Friday night before going out for a drink, the drunk scientist has an epiphany. "Aha!" he says to himself, "I've got it! Soda causes hangovers!"

In the immortal words of Andrew Schlafly: "In Romania, abortion was illegal under two decades of rule by the communist dictator Nicolae Ceausescu, and the country enjoyed one of the lowest breast cancer rates in the entire world during that time, far lower than comparable Western countries."^[3] (Just because the breast cancer rate went down does not mean that the illegality of abortions caused it.)

A man takes a vaccine and dies weeks later. The cause is blamed on the vaccine, instead of pre-existing health conditions.^[4]

When compared on a graph, the number of deaths by falling and drowning in a swimming pool correlates with the number of movies that Nick Cage is in. This is completely coincidental… Unless it's not.^[5]

The obvious caveat

Note that this fallacy can be partly logically valid, in that "Every time I've seen an X, there was a Y nearby" is usually good cause for further investigation. For example, "Just about everybody I know who smokes Lucky Strike cigarettes gets lung cancer" was a valid place to start an investigation into what was later realized to be the smoking-cancer connection — although the causation was partly wrong: by no means was the connection confined to one brand.

Just keep in mind the causation might be different than you might expect; for one obvious example, "fat people eat more diet food" does not mean "diet food causes fatness".^{[note 1]} Our Correlation does not imply causation article has more on the various possible causality directions of a real correlation.

External links

See the Wikipedia article on Post hoc ergo propter hoc.
Do you know why we lost Texas?
Post Hoc, Fallacy Files
Post Hoc Ergo Propter Hoc, Bruce Thompson
Spurious correlations, Tyler Vigen

Notes

↑ Although this particular point can be (and has been) argued about in the real world, depending on the diet food, for our purposes it's sufficient to note that people who are already fat might go for diet food in hopes of lowering their weight as a more plausible counter-explanation.

References

↑ Glenn, Cheryl; Loretta Gray. Hodges' Harbrace Handbook. 16^th ed. Thomson: Boston, 2007: p. 480.
↑ The Fine Art of Baloney Detection, Carl Sagan
↑ Strange bedfellows.
↑ https://healthfeedback.org/claimreview/frequency-of-deaths-in-elderly-individuals-after-covid-19-vaccination-werent-higher-than-the-frequency-in-those-who-werent-vaccinated/
↑ Cage movies and drowning, Tyler Vigen

[6] Although this particular point can be (and has been) argued about in the real world, depending on the diet food, for our purposes it's sufficient to note that people who are already fat might go for diet food in hopes of lowering their weight as a more plausible counter-explanation.

[1] Glenn, Cheryl; Loretta Gray. Hodges' Harbrace Handbook. 16^th ed. Thomson: Boston, 2007: p. 480.

[2] The Fine Art of Baloney Detection, Carl Sagan

[3] Strange bedfellows.

[4] ttps://healthfeedback.org/claimreview/frequency-of-deaths-in-elderly-individuals-after-covid-19-vaccination-werent-higher-than-the-frequency-in-those-who-werent-vaccinated/

[5] Cage movies and drowning, Tyler Vigen

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[note 1]

v - t - e Articles about logical fallacies
Informal fallacies:			Appeal to tradition • Appeal to novelty • Appeal to nature • Argument from morality • Argumentum ad martyrdom • Big words • Certum est quia impossibile est • Morton's fork • Friend argument • Exception that proves the rule • Extended analogy • Hindsight bias • Race card • Moralistic fallacy • Release the data • Gish Gallop • Terrorism-baiting • Uncertainty tactic • Greece-baiting • Ham Hightail • Red-baiting • Gore's Law • Nazi analogies • Mistaking the map for the territory • Red herring • Quidquid latine dictum sit, altum videtur • Presentism • Sunk cost • Two wrongs make a right • Flying carpet fallacy • My enemy's enemy • Appeal to ancient wisdom • Danth's Law • Argumentum ad lunam • Balance fallacy • Golden hammer • Loaded question • Escape to the future • Word magic • Spider-Man fallacy • Sanctioning the devil • Appeal to mystery • Informal fallacy • Common sense • Post-designation • Hyperbole • Relativist fallacy • Due diligence • Straw man • Good old days • Appeal to probability • Infinite regress • Circular reasoning • Media was wrong before • Is–ought problem • Ad iram • Just asking questions • Pink-baiting • Appeal to faith • Appeal to fear • Appeal to bias • Appeal to confidence • Appeal to consequences • Appeal to emotion • Appeal to flattery • Appeal to gravity • Appeal to hate • Argument from omniscience • Argument from silence • Argumentum ad baculum • Argumentum ad fastidium • Association fallacy • Broken window fallacy • Category mistake • Confounding factor • Counterfactual fallacy • Courtier's Reply • Damning with faint praise • Definitional fallacies • Equivocation • Fallacy of accent • Fallacy of accident • Fallacy of amphiboly • Gambler's fallacy • Imprecision fallacy • Moving the goalposts • Nirvana fallacy • Overprecision • Pathos gambit • Pragmatic fallacy • Quote mining • Argumentum ad sarcina inserta • Science doesn't know everything • Slothful induction • Spotlight fallacy • Style over substance • Toupee fallacy • Genuine but insignificant cause • Argument from incredulity • Appeal to age • Argumentum ad nauseam • Phantom distinction • Appeal to common sense • Argumentum ad hysteria • Omnipotence paradox • Argument from etymology • Appeal to trauma • Countless counterfeits fallacy •
	Ad hoc:		No True Scotsman • Moving the goalposts • Escape hatch • Handwave • Special pleading • Slothful induction • Nirvana fallacy • God of the gaps • PIDOOMA • Ad hoc • Tone argument •
	Arguments from ignorance:		Science doesn't know everything • Argument from incredulity • Argument from silence • Toupee fallacy • Appeal to censorship • Science was wrong before • Holmesian fallacy • Argument from omniscience • Willful ignorance • Argument from ignorance •
	Causation fallacies:		Correlation does not imply causation • Wrong direction • Counterfactual fallacy • Regression fallacy • Gambler's fallacy • Denying the antecedent • Genuine but insignificant cause •
	Circular reasoning:		Infinite regress • Argument by assertion • Argumentum ad dictionarium • Appeal to faith • Circular reasoning • Self-refuting idea •
	Emotional appeals:		Appeal to fear • Appeal to emotion • Appeal to confidence • Deepity • Argumentum ad baculum • Appeal to shame • Appeal to flattery • Tone argument • Appeal to money • Argumentum ad fastidium • Appeal to gravity • Appeal to consequences • Loaded language • Style over substance • Appeal to pity • Appeal to hate • Pathos gambit • Shaming • Degenerate • Abomination •
	Fallacies of ambiguity:		Fallacy of accent • Equivocation • Fallacy of amphiboly • Quote mining • Fallacy of ambiguity • Moral equivalence • Scope fallacy • Suppressed correlative • Not as bad as • Etymology • Continuum fallacy • Wronger than wrong • Definitional fallacies • Code word • Phantom distinction •
Formal fallacies:			Confusion of the inverse • Denying the antecedent • Non sequitur • Affirmative conclusion from a negative premise • Not even wrong • Chewbacca Defense • Affirming a disjunct • Illicit process • Four-term fallacy • Negative conclusion from affirmative premises • Fallacy fallacy • Substituting explanation for premise • Enthymeme • Syllogism • Formal fallacy • Existential assumption • Masked man fallacy • Self-refuting idea • Argument by gibberish • One single proof • Affirming the consequent • False dilemma • Conjunction fallacy •
Fallacious arguments:			Bumblebee argument • Fatwa envy • Gotcha argument • Hoyle's fallacy • Intuition pump • Logic and Creation • Not Circular Reasoning • Peanut butter argument • Great Beethoven fallacy • Fallacy of unique founding conditions • Evil is the absence of God • Argument from first cause • How do you know? Were you there? • Argument from design • Argument from beauty • Appeal to nature • Solferino fallacy • Religious scientists • Nothing to hide • Argument from fine tuning • Creep shaming • "I used to be an atheist" • Atheism as a religion • Argumentum ad populum • Argument from morality • Anti-environmentalism • Appeal to bias • Apophasis • Argumentum ad nauseam • Appeal to censorship • Argumentum ad sarcina inserta • Blaming the victim • Bait-and-switch • Danth's Law • Chewbacca Defense • Canard • DARVO • Demonization • Escape hatch • Friend argument • Everyone is racist • Gish Gallop • Greece-baiting • Gore's Law • Ham Hightail • Just asking questions • Leading question • Loaded language • Linking to authority • Loaded question • Lying by omission • Motte and bailey • Nazi analogies • Moving the goalposts • One single proof • Pink-baiting • One-way hash argument • Pathos gambit • Quote mining • Poisoning the well • Quidquid latine dictum sit, altum videtur • Race card • Red-baiting • Red herring • Release the data • Science was wrong before • Shill gambit • Straw man • Silent Majority • Uncertainty tactic • Style over substance • Terrorism-baiting • Weasel word • What's the harm (logical fallacy) • Whataboutism • Bullshit • Logical fallacy • Banana argument • Scapegoat • How come there are still monkeys? • Anti-racist is a code word for anti-white • Ontological argument • Omnipotence paradox • Presuppositionalism • Just a joke • Countless counterfeits fallacy •
Conditional fallacies:			Slippery slope • What's the harm (logical fallacy) • Special pleading • Conditional fallacy • On the spot fallacy • Appeal to the minority • Argumentum ad populum • Galileo gambit • Professor of nothing •
	Genetic fallacies:		Genetic fallacy •
		Appeals to authority:	Ipse dixit • Appeal to confidence • Argumentum ad populum • Argument from authority • Linking to authority • Silent Majority • Invincible authority • Appeal to celebrity • Ultracrepidarianism • Appeal to the minority • Galileo gambit • Appeal to identity • Weasel word • Professor of nothing • Euthyphro dilemma • Divine command theory •
		Ad hominem:	Ad iram • Argumentum ad cellarium • Bulverism • Poisoning the well • Blaming the victim • Tu quoque • Whataboutism • Nutpicking • Jonanism • Demonization • Shill gambit • Appeal to bias • Fallacy of opposition • Association fallacy • Damning with faint praise • Pathos gambit • Appeal to identity • Argumentum ad hominem • Nazi analogies • Not an argument • Nothing to hide • Scapegoat • 地下室论证 •
	Imprecision fallacies:		Apex fallacy • Overprecision • Cherry picking • Overgeneralization • Texas sharpshooter fallacy • False analogy • Appeal to fiction • Spotlight fallacy • Pragmatic fallacy • Selection bias • Anecdotal evidence • Category mistake • Nutpicking • Imprecision fallacy • Confounding factor • Fallacy of accident • Neyman's bias •
Valid logical methods:			Rapoport's Rules • Negative evidence • Reductio ad absurdum •
Fallacy collections:			SeekFind • Nizkor Project • Fallacy Files • Your Logical Fallacy Is • Logically Fallacious •

Post hoc, ergo propter hoc

Contents

Alternate names

Form of the argument

Other examples

The obvious caveat

See also

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External links

Notes

References

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