Post hoc fallacy

The post hoc fallacy means "after this, therefore because of this". Its Latin name is Post hoc ergo propter hoc. It is a logical fallacy. When event B happens after event A, a person might think  "event A must have caused event B".

Example: 
The rooster crows immediately before sunrise.
Therefore the rooster causes the Sun to rise.

The term “coincidence does not equal causation” applies here because there is no provable outcome that is anything more than being purely coincidental after some unrelated event occurred. 

It is a tempting error because sequence in time does sometimes suggest causality.Damer, T Edward 1995. ''Attacking faulty reasoning: a practical guide to fallacy-free arguments. 3rd ed, Belmont, CA: Wadsworth, p131. . When I press the light switch, the light comes on, and that is a cause and effect sequence. The difference is that it can be explained why the light comes on when the switch is pressed. On the other hand, no-one can explain why a rooster's crowing might affect the Sun.

 Popular culture 
The phrase is used by the character Sheldon Cooper in the third season of The Big Bang Theory. Sheldon mentions the logical fallacy in disputing his mother's claim that her prayer group did ensure his safety during his North Pole expedition.

References



Category:Logical fallacies