Assemblies of bishops to decide questions of doctrine and ecclesiastical discipline. They are oecumenical, national, or provincial, according as the bishops assembled represented the whole Church, a merely national one, or a provincial section of it. Eastern: Nice, 325 (at which Arius was condemned), 787; Constantinople, 381 (at which Apollinaris was condemned), 553, 680, 869; Ephesus, 431 (at which Nestorius was condemned); Chalcedon, 451 (at which Eutyches was condemned). Western: Lateran, 1123, 1139, 1179, 1215, 1274; Synod of Vienne, 1311; Constance, 1414; Basel, 1431-1443; Trent, 1545-1563; Vatican, 1869.