In all ages of the world, priests have been enemies to liberty; and it is certain, that this steady conduct of theirs must have been founded on fixed reasons of interest and ambition. Liberty of thinking, and of expressing our thoughts, is always fatal to priestly power, and to those pious frauds, on which it is commonly founded; and, by an infallible connexion, which prevails among all kinds of liberty, this privilege can never be enjoyed, at least has never yet been enjoyed, but in a free government.

Part I, Essay 9: Of The Parties of Great Britain - Essays, Moral, Political, and Literary (1741-2; 1748)