Hyacinthe Sigismond Gerdil, a Savoyard philosopher, born at Samoens, June 23, 1718, died in Rome, Aug. 12, 1802. He became a Barna-bite, studied theology in Bologna, won the friendship of Cardinal Lambertini, afterward Pope Benedict XIV., and became professor of philosophy at Macerata, at Casale, and finally at Turin. Refusing the dignity of general of his order, he became tutor to the prince of Piedmont, afterward Charles Emanuel IV. of Sardinia, the rich abbey of Chiusa being given him, whose revenues he devoted to charity. His first works were Eclaircissements sur la notion et la divisihilite de Vetendue geometrique (Turin, 1741), and Immaterialite de Vdme de-montree contre Locke (1747). To these works succeeded almost every year until his death others in Latin, French, or Italian, on questions of theology, philosophy, physical or mathematical science, and sociology. He was created a cardinal in petto by Clement XIV., and officially proclaimed as such in 1777 by Pius VI. Appointed prefect of the Propaganda, protector of the Maronites, and corrector of oriental publications, he led in Rome a life of the most laborious poverty.

He sold his library in 1798 in order to support himself, followed Pius VI. to Siena, and would have been unanimously chosen by the conclave as his successor, if the fact of his being a native of Savoy, then a part of France, had not caused Austria to oppose him. His complete works were published in Rome (20 vols. 8vo, 1806-'21). An edition of his select works in 12 vols, was begun in Paris in 1826, but only 2 vols, have appeared. In 1863 Migne published a selection of his theological works in 1 vol. large 8vo.