''Post hoc ergo propter hoc'' (
Latin
Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
: 'after this, therefore because of this') is an
informal fallacy
Informal fallacies are a type of incorrect argument in natural language. The source of the error is not just due to the ''form'' of the argument, as is the case for formal fallacies, but can also be due to their ''content'' and ''context''. Fallac ...
that states "Since event Y ''followed'' event X, event Y must have been ''caused'' by event X." It is a fallacy in which an event is presumed to have been caused by a closely preceding event merely on the grounds of temporal succession. This type of reasoning is fallacious because mere temporal succession does not establish a causal connection. It is often shortened simply to ''post hoc fallacy''. A
logical fallacy of the
questionable cause variety, it is subtly different from the fallacy ''
cum hoc ergo propter hoc'' ('with this, therefore because of this'), in which two events occur simultaneously or the chronological ordering is insignificant or unknown. Post hoc is a logical fallacy in which one event seems to be the cause of a later event because it occurred earlier.
''Post hoc'' is a particularly tempting error because correlation sometimes appears to suggest
causality. The fallacy lies in a conclusion based ''solely'' on the order of events, rather than taking into account other factors potentially responsible for the result that might rule out the connection.
A simple example is "The
rooster crows immediately before
sunrise; therefore the rooster causes the sun to rise."
Pattern
The form of the ''post hoc fallacy'' is expressed as follows:
:* A occurred, then B occurred.
:* Therefore, A caused B.
When B is undesirable, this pattern is often combined with the
formal fallacy
In logic and philosophical logic, philosophy, a formal fallacy is a pattern of reasoning rendered validity (logic), invalid by a flaw in its logical structure. propositional calculus, Propositional logic, for example, is concerned with the meaning ...
of
denying the antecedent, assuming the
logical inverse holds: believing that avoiding A will prevent B.
Examples
* A tenant moves into an apartment and the building's furnace develops a fault. The manager blames the tenant's arrival for the malfunction. One event merely followed the other, in the absence of causality.
* Brazilian footballer
Pelé
Edson Arantes do Nascimento (; 23 October 1940 – 29 December 2022), better known by his nickname Pelé (), was a Brazilian professional Association football, footballer who played as a Forward (association football), forward. Widely reg ...
blamed a dip in his playing performance on having given his playing shirt to a fan. His play recovered after a friend, sent to retrieve the shirt from the fan, returned a shirt claimed to be the original (though it was actually just the shirt Pelé had worn during his previous poor performance, as the original could not be tracked down).
* Reporting of coincidental
vaccine adverse events, where people have a health complaint after being vaccinated and assume it was caused by the vaccination.
See also
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Texas sharpshooter fallacy
Bibliography
# Woods, J. H., Walton, D. N. (1977). Post Hoc, Ergo Propter Hoc.
# Mommsen, J. K. F. (2013). Wider Das Post Hoc Ergo Propter Hoc - Primary Source Edition. United States: BiblioLife.
# Woods, J., Walton, D. (2019). Fallacies: Selected Papers 1972–1982. Germany: De Gruyter.
References
{{Time in philosophy
Causal fallacies
Latin logical phrases