Post hoc ergo propter hoc (
Latin: "after this, therefore because of this") is a
logical fallacy (of the
questionable cause variety) that states "Since event Y
followed event X, event Y must have been
caused by event X." It is often shortened to simply
post hoc fallacy. It is subtly different from the fallacy
cum hoc ergo propter hoc ("with this, therefore because of this"), in which two things or events occur simultaneously or the chronological ordering is insignificant or unknown.
Post hoc is a particularly tempting error because temporal sequence appears to be integral to
causality. The fallacy lies in coming to a conclusion based
solely on the order of events, rather than taking into account other factors that might rule out the connection.