Darryl and Harold were the best patients in a mental institution
The place had an unusual annual contest, picking two of the best patients and giving them two questions.
If they got them correct, they were deemed cured and free to go
Darryl was called into the doctor's office first and asked if he understood that he'd be free if he answered the questions correctly
Darryl said “yes” and the doctor proceeded.
“Darryl, what would happen if I poked out one of your eyes?”
Darryl said, “I'd be half blind.”
What if I poked out both eyes?”
“I'd be completely blind.”
The doctor stood up, shook Darryl's hand, and told him he was free to go.
On Darryl's way out, as the doctor filled out the paperwork, Darryl mentioned the exam to Harold, who was seated in the waiting room
He told him what questions were going to be asked and gave him the answers.
So Harold went into the doctor's office when he was called
The doctor went through the formalities and then asked, “What would happen if I cut off one of your ears?”
Remembering what Darryl had told him, he answered, “I'd be half blind.” The doctor looked a little puzzled, but went on
“What if I cut off the other ear?”
“I'd be completely blind,” Harold answered.
“Harold, can you explain how you'd be blind?”
“My hat would fall down over my eyes.”