'In my Opinion, you are not unlike the Moors, who are incapable of being convinc'd of the Error of their Religion, by Scripture, speculative Reasons, or those drawn immediately from the Articles of our Faith; and will yield to nothing but Demonstrations, as evident as those of the Mathematicks, and which can as little be deny'd, as when we say, If from two equal Parts, we take away two equal Parts, the Parts that remain are also equal. And when they do not understand this Proposition, which they seldom do, we are oblig'd by Operation, to make it yet more plain and obvious to their Senses; and yet all this Labour will at last prove ineffectual to the convincing them of the Verities of our Religion.'
--Don Quixote, Part I, Book IV, Chapter VI, 'The Novel of the Curious Impertinent'
(The joke is that the mathematical process described here is Algebra, learned by the Europeans from the Moors.)
