Charles Irenee Castel Saint-Pierre, abbé de, a French philanthropist, born near Barfleur, Normandy, Feb. 18; 1658, died in Paris, April 29, 1743. He was educated by the Jesuits at Caen and joined the priesthood. In 1686 he went to Paris with the geometrician Varignon, and in 1695 succeeded Bergeret in the academy. In 1702 he became chaplain of the bishop of Orleans, who obtained for him the abbey of Tiron. In 1712 he attended the congress of Utrecht with Cardinal Polignac. His Projet de paix perpétuelle (3 vols., Utrecht, 1713-'17) was followed in 1718 by Discours sur la polysynodic, in which he severely judged Louis XIV., and advocated constitutional government. He was consequently expelled from the academy, but an association known as club de l'entresol gave him opportunities to expound his humanitarian schemes, and became the nucleus of the future academy of moral and political sciences. The club was closed in 1731 by Cardinal Fleury, after seven years' existence. Most of his writings are included in his Ouvrages de politique et de morale (18 vols., Rotterdam, 1738-41).