A man visits the doctor because he’s suffering from a miserable winter cold. His doctor prescribes some antibiotics, but they don’t help. On his next visit, the doctor gives the man a shot, but it doesn’t do any good. On his third visit, the doctor tells the man to go home and take a steaming hot bath. As soon as he gets out of the bath, he should open all of the windows in his house and stand naked in the draft.

“But doctor,” the man protests, “if I do that, I’ll probably get pneumonia.”

“I know,” says the doctor. “But at least I know how to cure pneumonia.”