The expression post hoc ergo propter hoc, Latin for "after this, therefore because of this,” is a well-worn logical fallacy based upon the mistaken notion that simply because one thing happens after another, the first was necessarily a cause of the second. This conclusion is, of course, incorrect. Many events follow in sequence without being causally related. A baseball player wears a particular shirt one day and hits a home run, for example. Although someone following post hoc logic might believe the two events to be causally related, they’d be wrong. Coincidences happen.
The obvious flaw in such post hoc reasoning, however, has yielded a peculiarly damaging result with respect to federal laws forbidding retaliation against employees engaging in “protected activities” such as filing a complaint of sexual or racial discrimination. The typical scenario goes something like this. Employee files a charge with Company alleging sexual harassment by Supervisor. Charge disappears into the bowels of Company’s Human Resources Office. One week later, Employee finds herself miserable and alone working the graveyard shift.
If Supervisor moved Employee to the graveyard shift because of the harassment charge, he has unlawfully retaliated against her. When Employee tries to file her complaint, however, the only evidence she’s going to have is the temporal sequence of events. “I filed a charge and was moved to graveyard one week later.”
Company’s lawyer, if he’s worth anything, will move for dismissal, arguing that Employee’s “post hoc ergo propter hoc” logic is insufficient. And in most federal courts, particularly the more conservative ones, he’ll win, because the Court will jump to the equally incorrect conclusion that because temporal sequence alone doesn’t prove causation, no causation occurred. Sort of a “two logical wrongs don’t make a right” kind of deal.
BrevityQuest 2007