Calling in his next patient, the Doctor invited him to sit down and asked what the problem was.
"I keep thinking that I'm a moth" the patient explained.
- "Well, that's certainly an unusual complaint", stroking his beard, the doctor crossed his legs and sat back in his chair. "But I really think that you would be better speaking to a psychiatrist rather than a general practitioner like me".
"Oh I know that!" The patient smiled. "I already have an appointment at a psychiatric unit next week".
"So", puzzled, the Doctor enquired, "If you have an appointment already booked about thinking you're a moth....Why did you come in here?"
...
The patient replied
"I saw the light was on"