David Hume on Religious HypocrisyA Natural History of Religion (1757), Part XV.
Hear the verbal protestations of all men: Nothing so certain as their religious tenets. Examine their lives: You will scarcely think that they repose the smallest confidence in them. The greatest and truest zeal gives us no security against hypocrisy: The most open impiety is attended with a secret dread and compunction. No theological absurdities so glaring that they have not, sometimes, been embraced by men of the greatest and most cultivated understanding. No religious precepts so rigorous that they have not been adopted by the most voluptuous and most abandoned of men. … Look out for a people, entirely destitute of religion: If you find, them at all, be assured, that they are but few degrees removed from brutes. What so pure as some of the morals, included in some theological system? What so corrupt as some of the practices, to which these systems give rise?