Council, or SYNOD, an assembly of ecclesiastics met to regulate doctrine or discipline. We first hear of such assemblies during the Montanist controversy, about 150 A.D. Ecumenical councils are convoked from all parts of Christendom, and claim to regulate the affairs of the whole church. Other synods have represented the East and West respectively. Patriarchal, national, and primatial councils represent a whole patriarchate, a nation, or the several provinces subject to a primate, while the bishops and other dignitaries of a province constitute a provincial; the clergy of a diocese under the presidency of the bishop, a diocesan council. Mixed councils during the middle ages dealt with civil as well as ecclesiastical affairs, and were composed of secular persons as well as churchmen. Sometimes, but not always, the lay and ecclesiastical members voted in separate chambers.
The first eight general councils were convoked by the emperor, all the later ones by the popes, and the fifth Lateran Council asserts (Sess. xi.) the modern principle that the right of convoking, removing, and dissolving general councils belongs to the pope. The right of voting was reserved in early times to bishops and priests, or deacons who acted as representatives of absent bishops. From the 7th century onwards this right was sometimes extended to abbots, and from the end of the medieval period to cardinals who were not also bishops. At the Vatican Council the members entitled to vote were cardinals, bishops (even if only titular bishops), mitred abbots, and generals of religious orders. Priests acting as proxies of bishops were not admitted. The presidency at the early ecumenical councils followed no fixed rule. In a certain sense it belonged to the emperor, who had convoked the bishops, and was responsible for peace and order. 'It was not,' says Harnack (Dogmengeschichte, ii. p. 101), 'till the fourth general council that the papal legates gained a unique position, and learned Catholics have admitted that the presidency of the papal legates at Nicæa does not admit of positive proof.' This is true even of Catholic theologians writing after the Vatican decrees. Thus Kraus (Kirchengeschichte, p. 147) contents himself with maintaining 'the probability' that the papal legates presided at Nicæa, and Hefele (Concil. i. p. 38, 2d ed.) admits that the question is 'not without difficulty.' The modern theory that a council is then, and then only, to be counted general when its acts have been ratified by the pope, is of still later origin. Even medieval theologians, such as Thomas of Walden, maintained that the decisions of general councils did not acquire binding force till they had been accepted by the whole church. And although it was an established principle in the 6th and the following centuries that the definitions of councils, indisputably œcuménical, could not be called in question, it is certain that St Augustine had been of another mind. He asserts (De Bapt. contra Donat. ii. p. 3-4) that Scripture alone has final and irreformable authority, but that even 'plenary councils, assembled from the whole Christian world,' may be 'corrected' (emendari) by the accession of knowledge and experience. Moreover, the fact that the decisions even of provincial councils are sometimes attributed, in the 4th century, to the 'suggestion' of the Holy Spirit, shows that caution is needed in interpreting the rhetorical language of early writers.
The Greek Church recognises seven general councils—viz.: (1) The first of Nicæa, 325 A.D.; (2) the first of Constantinople, 381; (3) Ephesus, 431; (4) Chalcedon, 451; (5) second of Constantinople, 553; (6) third of Constantinople, 680; (7) second of Nicæa, 787. To these Roman Catholics add: (8) fourth of Constantinople, 869; (9) first Lateran, 1123; (10) second Lateran, 1139; (11) third Lateran, 1179; (12) fourth Lateran, 1215; (13) first of Lyons, 1245; (14) second of Lyons, 1274; (15) Vienne, 1311; (16) Constance, 1414-18, of which Ultramontanes accept only the decrees passed in sessions 42d to 45th inclusive, and such decrees of earlier sessions as were approved by Martin V.; (17) Basel, 1431 and the following years, œcuménical according to Ultramontanes only till the end of the twenty-fifth session, and even then only in respect of such decrees as were approved by Eugenius IV.; (18) Ferrara-Florence, 1438-42, really a continuation of Basel; (19) fifth Lateran, 1512-17; (20) Trent, 1545-63; (21) Vatican, December 8, 1869, to July 18, 1870, and still unfinished.
The best collections of councils are by Hardouin (12 vols. folio, Paris, 1715), and that of Mansi (31 vols. folio, Florence, 1759), which is by far more complete than Hardouin's, but inferior to it in correctness of typography. An excellent account of the councils, with the text of the most important decrees, will be found in Bishop Hefele's Konziliengeschichte (7 vols. 1855-74; continued by Hergenröther and then Knöpfler, vols. viii.-ix., 1887-90; Eng. trans., vols. i.-iv., 1871-95). For the more important councils, see NICÆA, BASEL, &c.