"I have been insisting to all my colleagues in the philosophy department, and elsewhere, that Conan Doyle's 'detective' has found the solution to our human folly: close observation of 'clues,' and shrewd 'ratiocination.'"
-- Joyce Carol Oats, The Accursed, 2013
By a not uncommon process of ratiocination, Mrs. Fetherel's success had convinced her of her vocation.
-- Edith Wharton, "Expiation," Cosmopolitan, 1908
Ratiocination is derived from the Latin word ratiōcinārī meaning "to reckon, calculate, conclude" which in turns come from the root ratiō meaning "reason."