The "Post Hoc Ergo Propter Hoc" Fallacy

The "Post hoc ergo propter hoc" fallacy is a common mistake in the diagnosis and treatment of medical and psychological conditions. "Post hoc ergo propter hoc" is Latin for "After this, therefore because of this" or in other words "If A happened then B happened, then A must have caused B to happen".

"Post hoc ergo propter hoc" is Latin for "After this, therefore because of this" or in other words "If event B happens after event A, then A must have caused B to happen".

Examples of the "post hoc ergo propter hoc" fallacy:

• A train always passes after the railroad crossing alarm sounds and the gates come down. Therefore the railroad crossing causes the train to pass.
• I wore my purple sweater and my team won against all the odds. Therefore I am going to wear that sweater to every game.
• Most divorced couples go to see a therapist before they separate. Therefore going to see a therapist will increase the chances that you will get a divorce.
• Children of divorce, on average, perform poorer academically. Therefore, if you get a divorce you will hurt your child's chances of going to college.
• Since we moved in together she has become very depressed. I feel like I've ruined her life.
• Since I stopped smoking we haven't had an argument. Who knew the answer could have been so simple?