A patient in a mental hospital would spend his entire day with his ear pressed up against a wall. The doctor would watch this man, day after day, sit against the wall. The doctor finally decides to see what the patient is always listening to, so he puts his ear up to the wall and listens alongside the man. He hears nothing.

He turns to the mental patient and says, “I don’t hear anything coming from the wall.”

The mental patient replies, “Yeah, I know, and it’s been like that for months!”