Those Times and These by Irvin S. Cobb

SO many things that at first seem amazingly complex turn out amazingly simple. The purely elemental has a trick of ambushing itself behind a screen of mystery; but when by deduction and elimination -- in short, by the simple processes of subtraction and division -- we have stripped away the mask, the fact stands so plainly revealed we marvel that we did not behold it from the beginning. Elemental, you will remember, was a favourite word with Mr. Sherlock Holmes, and one much employed by him in the elucidation of problems in criminology for the better enlightenment of his sincere but somewhat obvious-minded friend, the worthy Doctor Watson.

On the other hand, traits and tricks that appear to betray the characters, the inclinations and, most of all, the vocations of their owners may prove misleading clues, and very often do. You see a black man with a rolling gait, who spraddles his legs when he stands and sways his body on his hips when he walks; and, following the formula of the deductionist cult of amateur detectives, you say to yourself that here, beyond peradventure, is a deep-water sailor, used to decks that heave and scuppers that flood. Inquiry but serves to prove to you how wrong you are. The person in question is a veteran dining-car waiter.