The Ecumenical Councils

Nicaea I

The first ecumenical council held in 325, condemned Arianism, defined the consubstantiality of the Father and the Son.

Arianism

A heresy that denied the divinity of Christ, condemned at the Council of Nicaea I.

Nicaea-Constantinopolitan Creed

The creed formulated during Nicaea I that defined essential Christian beliefs, later completed at Constantinople I.

Constantinople I

The second ecumenical council held in 381 that reaffirmed the outcome of Nicaea I and condemned Macedonianism.

Macedonianism

A heresy that denied the divinity of the Holy Spirit, condemned at the Council of Constantinople I.

Theotokos

A title for Mary meaning 'Mother of God,' defined at the Council of Ephesus.

Ephesus

The third ecumenical council held in 431 that condemned Nestorianism and affirmed Mary as the Mother of God.

Nestorianism

A heresy that denied the unity of divine and human in Christ, condemned at the Council of Ephesus.

Chalcedon

The fourth ecumenical council held in 451 that condemned Monophysitism and affirmed the dual nature of Christ.

Monophysitism

A heresy that denied Christ's human nature, condemned at the Council of Chalcedon.

Constantinople II

The fifth ecumenical council held in 553 that condemned the Three Chapters, writings tainted by Nestorianism.

Monothelitism

The heresy that held Christ had only one will, condemned at the Council of Constantinople III.

Papal Infallibility

The doctrine that the Pope is incapable of error when pronouncing definitively on matters of faith or morals.

Lateran I

The first Lateran council held in 1123 that confirmed the Concordat of Worms.

Concordat of Worms

An agreement reached in 1122 to resolve the dispute over investiture between the Church and secular authorities.

Lateran IV

The fourth Lateran council held in 1215 that ordered annual reception of penance and the Eucharist.

Transubstantiation

The doctrine explaining the Real Presence of Christ in the Eucharist, discussed at Lateran IV.

Florence

The ecumenical council (1438-1443) that addressed papal primacy and temporarily united Eastern Churches with Rome.

Great Schism

The split in the Catholic Church resulting in rival claimants to the papacy, resolved at the Council of Constance.

Counter-Reformation

The period of Catholic revival initiated by the Council of Trent to respond to Protestant reforms.

Vatican II

The ecumenical council held from 1962-1965 aimed at renewal and reform of the Church in response to contemporary issues.

Pope Sylvester I

The Pope during the Nicaea I council (314-335) who presided over the meetings.