A happy man or woman is a better thing to find than a five-pound note. He or she is a radiating focus of goodwill; and their entrance into a room is as though another candle had been lighted. We need not care whether they could prove the forty-seventh proposition; they do a better thing than that, they practically demonstrate the great Theorem of the Liveableness of Life.

Robert Louis Stevenson (1850-1894) Scottish essayist, novelist, poet

Essay (1877-07), “An Apology for Idlers,” Cornhill Magazine, Vol. 36
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Euclid's 47th Proposition (in his Elements, Book 1) is the Pythagorean Theorem.Collected in Virginibus Puerisque and Other Papers, ch. 3 (1881).