Bishops gathered, sometimes for years, to argue, to condemn, to compromise, and to name the faith. Each entry includes the creed produced, the controversy resolved, and what the council actually decided.
The first council of the Church, resolving whether Gentile converts must follow Mosaic law.
The first ecumenical council, condemning Arianism and formulating the original Nicene Creed.
Reaffirmed Nicene orthodoxy, expanded the Creed's teaching on the Holy Spirit, and condemned lingering Arianism.
Condemned Nestorianism and affirmed Mary as Theotokos, 'God-bearer.'
Defined Christ as one person in two natures, fully God and fully man, against Monophysitism.
Restored the veneration of icons after the first period of Byzantine iconoclasm.
Defined transubstantiation, mandated annual confession and communion, and reformed church discipline broadly.
The Catholic Church's definitive response to the Protestant Reformation, clarifying doctrine and reforming discipline.
Defined papal infallibility amid the loss of the Papal States and rising modern rationalism.
A sweeping renewal (aggiornamento) of Catholic life, liturgy, and relations with the modern world and other Christians.