François VI, Duc de La Rochefoucauld, Prince de Marcillac (French: [fʁɑ̃swa d(ə) la ʁɔʃfuˈko]; 15 September 1613 – 17 March 1680) was a noted French author of maxims and memoirs. It is said that his world-view was clear-eyed and urbane, and that he neither condemned human conduct nor sentimentally celebrated it. Born in Paris on the Rue des Petits Champs, at a time when the royal court was vacillating between aiding the nobility and threatening it, he was considered an exemplar of the accomplished 17th-century nobleman. Until 1650, he bore the title of Prince de Marcillac.
You may find more from Francois de La Rochefoucauld on Wikiquote
The real existence of an enemy upon whom one can foist off everything evil is an enormous relief to one's conscience. You can then at least say, without hesitation, who the devil is; you are quite certain that the cause of your misfortune is outside, and not in your own attitude.