An ecumenical council, also called general council, is a meeting of bishops and other church authorities to consider and rule on questions of Christian doctrine, administration, discipline, and other matters in which those entitled to vote are convoked from the whole world (oikoumene) and which secures the approbation of the whole Church.

The word "ecumenical" derives from the Late Latin oecumenicus "general, universal", from Greek oikoumenikos "from the whole world", from he oikoumene ge "the inhabited world" (as known to the ancient Greeks); the Greeks and their neighbors, considered as developed human society (as opposed to barbarian lands); in later use "the Roman world" and in the Christian sense in ecclesiastical Greek, from oikoumenos, present passive participle of oikein ("inhabit"), from oikos ("house, habitation"). The first seven ecumenical councils, recognised by both the eastern and western denominations comprising Chalcedonian Christianity, were convoked by Roman Emperors, who also enforced the decisions of those councils within the state church of the Roman Empire.

Starting with the second ecumenical council, noteworthy schisms led to non-participation by some members of what had previously been considered a single Christian Church. Thus, some parts of Christendom did not attend later councils, or attended but did not accept the results. Bishops belonging to what became known as the Church of the East participated in the first two councils. Bishops belonging to what became known as Oriental Orthodoxy participated in the first five councils, but rejected the decisions of the fifth and did not attend any subsequent ecumenical councils. Bishops belonging to what then became known as the Catholic Church and Eastern Orthodox Church participated in seven ecumenical councils, as described below, but not the fourth one of those that the Oriental Orthodox bishops participated in.

Acceptance of councils as ecumenical and authoritative varies between different Christian denominations. Disputes over Christological and other questions have led certain branches to reject some councils that others accept.

Acceptance of councils by denomination The Church of the East accepts as ecumenical the first two councils. Oriental Orthodox Churches accept the first three, while some also accept the fourth one, the Second Council of Ephesus.

Both the Catholic Church and Eastern Orthodox Church recognize in whole or in part seven councils held between the 4th to the 9th centuries as ecumenical. Some Eastern Orthodox also accept one later council as ecumenical. The Catholic Church has continued to hold general councils of the bishops in full communion with the Pope, and recognizes a total of twenty-one councils as ecumenical.

The first three councils and the Council of Chalcedon are recognized by some Lutheran Churches, Anglican Communion and Reformed Churches—though they are "considered subordinate to Scripture". The Lutheran World Federation recognizes as "exercises of apostolic authority" the same seven Ecumenical Councils that both the Catholic Church and Eastern Orthodox Church accept in whole or in part, and recognizes their decisions as authoritative; while member churches are not required to accept all theological statements produced by the Federation, but only to subscribe to the most basic Lutheran historical confessional documents, most do follow this recommendation. The Anglican Communion "acknowledge the authoritative place of the Ecumenical Councils in the life of the Church." The Anglican Communion has further affirmed the following: The Anglican Communion has not expressly, or officially, defined, in its historic formularies or Canons, an exact number of those councils which it receives as Ecumenical, although there is a broad consensus in favour of the first four councils, and a respect for six and sometimes even seven.

Infallibility of ecumenical councils

The doctrine of the infallibility of ecumenical councils states that solemn definitions of ecumenical councils, which concern faith or morals, and to which the whole Church must adhere, are infallible. Such decrees are often labeled as 'Canons' and they often have an attached anathema, a penalty of excommunication, against those who refuse to believe the teaching. The doctrine does not claim that every aspect of every ecumenical council is dogmatic, but that every aspect of an ecumenical council is free of errors or impeccable.St Thomas Aquinas, S. Th. II, II, q. 11, a. 2 "Now a thing may be of the faith in two ways, in one way, directly and principally, e.g. the articles of faith; in another way, indirectly and secondarily, e.g. those matters, the denial of which leads to the corruption of some article of faith; and there may be heresy in either way, even as there can be faith." http://newadvent.org/summa/3011.htm#article2

Both the Catholic and the Eastern Orthodox churches uphold versions of this doctrine. However, the Catholic Church holds that solemn definitions of ecumenical councils meet the conditions of infallibility only when approved by the Pope,Vatican I, Dei Filius ch. 3 ¶ 1. Vatican II, Lumen Gentium § 25 ¶ 2. 1983 Code of Canon Law 749 § 2. while the Eastern Orthodox Church holds that an ecumenical council is itself infallible when pronouncing on a specific matter."The infallibility of the Church does not mean that the Church, in the assembly of the Fathers or in the expression of the Conscience of the Church, has already formally expressed all the truths of faith and norms. The infallibility of the Church is confined to the formulation of truths in question. This infallibility is not wholly God-inspired energy which would affect the participants of the synod to such an extent that they would be inspired to pronounce all the truths at one time as a whole system of a Christian catechism. The Synod does not formulate a system of beliefs encompassing all Christian teachings and truths, but only endeavours to define the particular disputed truth which was misunderstood and misinterpreted. The Church of Christ and its divine nature, as set forth above, is the foundation upon which the Eastern Orthodox Church [sic.] continues to administer and nourish its faithful, thereby protecting its fundamental essentials." Rev. George Mastrantonis, of the Greek Orthodox Archdiocese of America.

Protestant churches generally view ecumenical councils as fallible human institutions that have no more than a derived authority to the extent that they correctly expound Scripture (as most would generally consider occurred with the first three councils and the Council of Chalcedon in regard to their dogmatic decisions).Hans Schneider, "Councils of the Church", The Encyclopedia of Christianity (Grand Rapids, Michigan; Leiden, Netherlands: Wm. B. Eerdmans; Brill, 1999–2003), 701.

Council documents

Ecumenical councils were, from the beginning, bureaucratic exercises. Written documents were circulated, speeches made and responded to, votes taken, and final documents published and distributed. A large part of what is known about the beliefs of what was condemned as heresies by the councils comes from the documents the councils quoted in order to present refutations to them, or from deduction based on the refutations alone.

Most councils dealt not only with doctrinal but also with disciplinary matters, which were decided in canons ("laws"). Study of the canons of ecumenical councils is the foundation of the development of canon law, especially the reconciling of or determination of priority between seemingly contradictory canons. Canons consist of doctrinal statements and disciplinary measures—most ecumenical councils and local synods dealt with immediate disciplinary concerns as well as major difficulties of doctrine. Eastern Orthodoxy typically views the purely doctrinal canons as dogmatic and applicable to the entire church at all times, while the disciplinary canons apply to a particular time and place and may or may not be applicable in other situations.

Circumstances of the early ecumenical councils The ecumenical councils were successors to the earlier councils (also known as synods) held in the Empire before Christianity was made legal. These include the Council of Jerusalem (c. 50), the Council of Rome (155), the Second Council of Rome (193), the Council of Ephesus (193), the Council of Carthage (251), the Council of Iconium (258), the Council of Antioch (264), the Councils of Arabia (246–247), the Council of Elvira (306), the Council of Carthage (311), the Synod of Neo-Caesarea (c. 314), the Council of Ancyra (314) and the Council of Arles (314).

Of the seven councils recognised in whole or in part by both the Catholic and the Eastern Orthodox Church as ecumenical, all were called by a Roman emperor.Thomas J. Reese, Inside the Vatican: The Politics and Organization of the Catholic Church, (Harvard University Press, 1996), 35.Historical Theology: An Introduction to Christian Doctrine – Gregg Allison, Wayne Grude. mGoogle Books.The Ecumenical Patriarchate – Demetrius Kimina. sGoogle Books (27 March 2009). The emperor gave them legal status within the entire Roman Empire. All were held in the eastern part of the Roman Empire. The Bishop of Rome, self-styled as "pope" since the end of the fourth century, did not attend, although he sent legates to some of them.

Various theological and political differences led to parts of the Church to separate after some councils were held, with theological views on which councils were ecumenical becoming fragmented. The 431 Council of Ephesus—the third ecumenical council to be held—called by emperor Theodosius II to address a Christological dispute between the patriarchs Cyril of Alexandria and Nestorius of Constantinople. The attending bishops ended up fracturing into two separate synods after Cyril declared the council open prior to the arrival of the delayed delegation of eastern bishops headed by John I of Antioch, who upon arriving five days later and learning of Cyril's actions decided to declare the opening of the council by themselves and proceeded to support Nestorius. The result was the Nestorian schism between what came to be known as the Church of the East and wider Christendom.

Similarly, the Second Council of Ephesus of 449, also held in Anatolia, was called by the Byzantine Emperor Theodosius II and, though annulled by the Council of Chalcedon, was confirmed by Emperor Basiliscus, who annulled the Council of Chalcedon.

The Council of Hieria of 754, held at the imperial palace of that name close to Chalcedon in Anatolia, was summoned by Byzantine Emperor Constantine V and was attended by 338 bishops, who regarded it as the seventh ecumenical council. The Second Council of Nicaea, which annulled that of Hieria, was itself annulled at the synod held in 815 in Constantinople under Emperor Leo V. This synod, presided over by Patriarch Theodotus I of Constantinople, declared the Council of Hieria to be the seventh ecumenical council, but, although the Council of Hieria was called by an emperor and confirmed by another, and although it was held in the East, it later ceased to be considered ecumenical.

Catholic views on those circumstances The Catholic Church does not consider the validity of an ecumenical council's teaching to be in any way dependent on where it is held or on the granting or withholding of prior authorization or legal status by any state, in line with the attitude of the 5th-century bishops who "saw the definition of the church's faith and canons as supremely their affair, with or without the leave of the Emperor" and who "needed no one to remind them that Synodical process pre-dated the Christianisation of the royal court by several centuries".