Science is a first-rate piece of furniture for a man's upper chamber, if he has common sense on the ground-floor. But if a man has n't got plenty of good common sense, the more science he has the worse for his patient.
 Oliver Wendell Holmes Sr., The Poet at the Breakfast-Table (1872). copy citation

Context

“I 'll tell you what,—the Master said,—I know something about these young fellows that come home with their heads full of “science,” as they call it, and stick up their signs to tell people they know how to cure their headaches and stomach-aches. Science is a first-rate piece of furniture for a man's upper chamber, if he has common sense on the ground-floor. But if a man has n't got plenty of good common sense, the more science he has the worse for his patient. —I don't know that I see exactly how it is worse for the patient,—I said. —Well, I'll tell you, and you'll find it's a mighty simple matter. When a person is sick, there is always something to be done for him, and done at once.” source