If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, Does it contain any abstract reasoning concerning quantity or number? No. Does it contain any experimental reasoning, concerning matter of fact and existence? No. Commit it then to the flames: For it can contain nothing but sophistry and illusion.

Franklin, Benjamin. "Poor Richard’s Almanack, 1743." Benjamin Franklin: Autobiography, Poor Richard, and Later Writings, edited by J. A. Leo Lemay. Library of America, 2005.

Pascal, Blaise. "Pensées." Pensées and Other Writings, edited by Anthony Levi, translated by Honor Levi. Oxford University Press, 2008, no. 277.

Rousseau, Jean-Jacques. "Of the Social Contract." Of the Social Contract and Other Political Writings, translated by Quintin Hoare. Penguin Classics, 2012, bk. 4, ch. 7.