The story is told of five doctors went duck shooting one day. Included in the group were a GP, a pediatrician, a psychiatrist, a surgeon and a pathologist. After a time, a bird came flying overhead. The first to react was the GP who raised his shotgun, but then hesitated. "I'm not quite sure it's a duck," he said. "I think that I will have to get a second opinion." And of course by that time, the bird was long gone.

Another bird appeared in the sky thereafter. This time the pediatrician drew a bead on it. He too, however, was unsure if it was really a duck in his sights and besides, it might have babies. "I'll have to do some more investigations," he muttered, as the creature made good its escape.

Next to spy a bird flying was the sharp-eyed psychiatrist. Shotgun shouldered, he was more certain of his intended prey's identity. "Now, I know it's a duck, but does it know it's a duck?" The fortunate bird disappeared while the fellow wrestled with this dilemma.

Finally, a fourth fowl sped past and this time the surgeon's weapon pointed skywards. BOOM!! The surgeon lowered his smoking gun and turned nonchalantly to the pathologist beside him: "Go see if that was a duck, will you?"