Second Lateran Council, (1139), the 10th ecumenical council, convoked by Pope Innocent II. The council was convened to condemn as schismatics the followers of Arnold of Brescia, a vigorous reformer and opponent of the temporal power of the pope, and to end the schism created by the election of Anacletus II, a rival pope. Supported by St. Bernard of Clairvaux and later by Emperor Lothar II, Innocent was eventually acknowledged as the legitimate pope.
Besides reaffirming previous conciliar decrees, the Second Lateran Council declared invalid all marriages of those in major orders and of professed monks, canons, lay brothers, and nuns. The council repudiated the heresies of the 12th century concerning holy orders, matrimony, infant baptism, and the Eucharist. The Orthodox churches do not accept any of the five Lateran councils as truly ecumenical.