Post hoc, ergo propter hoc

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[[File:Post hoc ergo propter hoc.jpg|thumb|right|165px|An example observed in the wild]]
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'''''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.<ref>Glenn, Cheryl; Loretta Gray. ''Hodges' Harbrace Handbook.'' 16<sup>th</sup> ed. Thomson: Boston, 2007: p. 480.</ref><ref>[http://web.archive.org/web/20071022081018/http://rucus.ru.ac.za/~urban/docs/baloney.html The Fine Art of Baloney Detection], Carl Sagan</ref>

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 [[superstition]]s are formed based on [[Apophenia|seeing patterns]] in a series of [[coincidence]]s. 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==
{{syl
|2='''X''' happened before '''Y'''.
|4=([[Enthymeme|unstated]]) '''Y''' was caused by something (that happened before '''Y''').
|5=C|6=Therefore, '''X''' caused '''Y'''.}}

===Other examples===
Many [[superstition]]s 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 [[Alcohol|drunk]] [[scientist]] conducts an [[experiment]] to see why he gets [[hangover]]s. 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 [[West]]ern countries."<ref>[http://www.conservapedia.com/Abortion Strange bedfellows.]</ref> (Just because the breast [[cancer]] rate went down does not mean that the illegality of [[abortion]]s caused it.)

*A man takes a vaccine and dies weeks later. The cause is blamed on the vaccine, instead of pre-existing health conditions.<ref>https://healthfeedback.org/claimreview/frequency-of-deaths-in-elderly-individuals-after-covid-19-vaccination-werent-higher-than-the-frequency-in-those-who-werent-vaccinated/</ref>

*When compared on a graph, the number of [[death]]s 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.<ref>[http://www.tylervigen.com/view_correlation?id=359 Cage movies and drowning], ''Tyler Vigen''</ref>

==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 [[Tobacco smoking|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 that 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".<ref group=note>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.</ref> Our [[Correlation does not imply causation]] article has more on the various possible causality directions of a real correlation.

==See also==
{{otherlang
|es=Post hoc, ergo propter hoc (español)
|pt=Post hoc, ergo propter hoc (português)}}

==External links==
*{{wpa|Post hoc ergo propter hoc}}
*[http://www.youtube.com/watch?v=HL_vHDjG5Wk Do you know why we lost Texas?]
*[http://www.fallacyfiles.org/posthocf.html Post Hoc], [[Fallacy Files]]
*[http://web.archive.org/web/20070410064442/http://www.cuyamaca.net/bruce.thompson/Fallacies/posthoc.asp Post Hoc Ergo Propter Hoc], Bruce Thompson
*[http://tylervigen.com/spurious-correlations Spurious correlations], ''Tyler Vigen''

==Notes==
{{reflist|group=note}}

==References==
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[[Category:Latin phrases]]
[[Category:Causation fallacies]]

Categories: Latin phrases, Causation fallacies