University of Virginia Library

POST HOC ERGO PROPTER HOC:

the logical FALLACY which assumes that because "A" if it precedes or is the antecedent of "B" it causes "B." For example: someone who eats ice cream and then claims that the ice cream caused their headache has committed this fallacy. The ice cream may or may not have caused the headache but the observation that it preceded the headache does not prove that it caused it. Further investigation and evidence is needed to discover the true CAUSE which could be an allergic reaction to ice cream but not necessarily.