It was easier to know it than to explain why I know it. If you were asked to prove that two and two made four, you might find some difficulty, and yet you are quite sure of the fact.
Arthur Conan Doyle (1859-1930) British writer and physician
Story (1886-04), “A Study in Scarlet,” Part 1, ch. 3 [Holmes], Beeton’s Christmas Annual, Vol. 28 (1887-11-21)
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