Let's be honest. A True Scotsman might do just about anything after just a few gallons of beer.— Zach Wereweinersmith (@ZachWeiner) October 10, 2013
The “No True Scotsman” is a logical fallacy. It was named by British philosopher Anthony Flew. It works something like this:
Hamish McDonald, a Scotsman, sits down to breakfast with his morning newspaper. He reads a report of the actions of a terrible criminal in Brighton who has not yet been identified by the police. Hamish declares, “No Scotsman would do such a thing!”
The next day, he reads another news report of a different criminal whose ghastly crimes far exceed those of the attacker in Brighton. Police have caught the villain, who turns out to be a Scotsman. When confronted with this fact, Hamish declares, “No true Scotsman would do such a thing!”
The fallacy is that Hamish has made an inaccurate generalization. When faced with a counterexample, he declares that counterexample invalid and that his generalization is unfalsifiable.