""Detect quacks"? Yes do, for Heaven's sake; but know withal the men that are to be trusted! Till we know that, what is all our knowledge; how shall we even so much as "detect"? For the vulpine sharpness, which considers itself to be knowledge, and "detects" in that fashion, is far mistaken. Dupes indeed are many: but, of all dupes, there is none so fatally situated as he who lives in undue terror of being duped."