Grey Eminence: A Study in Religion and Politics is a book by Aldous Huxley published in 1941. It is a biography of François Leclerc du Tremblay, the French monk who served as advisor to Cardinal de Richelieu. He was also known as Father Joseph and as l'éminence grise; that phrase originally referred to du Tremblay. The best book on the intelligence operations of the French state" during the Thirty Years' War.