Post hoc ergo propter hoc (Latin: 'after this, therefore because of this') is aninformal fallacy that states "Since event Yfollowed event X, event Y must have beencaused 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 topost hoc fallacy. Alogical fallacy of thequestionable cause variety, it is subtly different from the fallacycum 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.[1]
Post hoc is a particularly tempting error because correlation sometimes appears to suggestcausality. The fallacy lies in a conclusion basedsolely on the order of events, rather than taking into account other factors potentially responsible for the result that might rule out the connection.[2]
A simple example is "Therooster crows immediately beforesunrise; therefore the rooster causes the sun to rise."[3]
The form of thepost hoc fallacy is expressed as follows:
WhenB is undesirable, this pattern is often combined with theformal fallacy ofdenying the antecedent, assuming thelogical inverse holds: believing that avoidingA will preventB.[4]
