After a stunningly successful career, a mathematics professor went insane, thinking he was the differentiation operator. At the asylum he terrorized the other patients. He would run up to them and scream,
"I differentiate you! I differentiate you!"
The other patients would huddle in fear and begin sobbing. One day a new patient arrived and the insane professor started screaming at him,
"I differentiate you! I differentiate you!"
The patient didn't respond in the slightest. The professor screamed again,