Twenty-one times in sixteen hundred years the bishops of the whole Church have met to settle something. Between them they gave us the Creed we say on Sundays, the words for who Christ is, the canon of Scripture, the seven sacraments, and the shape of nearly everything else this site describes. Here is each one: where it met, what it faced, what it actually defined — with the texts quoted — and what it is popularly believed to have done but did not.
All 21 are mapped and dated. Every one has been written.
Click a pin to read what met there · the trace follows the councils in order, and shows where the Church’s centre of gravity moved
The First Seven
Held in the Greek East while the Church was still undivided, and received to this day by Catholics and Orthodox alike. Between them they settled who Christ is.
Nicaea I
Condemned Arius and confessed the Son consubstantial with the Father, giving the Church its first common Creed and a rule for dating Easter.
Constantinople I
Completed the Creed we still say, confessing the Holy Spirit as Lord and Giver of life, and gave Constantinople precedence after Rome.
Ephesus
Against Nestorius, defined that Mary is Theotokos, Mother of God, because the one born of her is a single person, the Word made flesh.
Chalcedon
Defined Christ as one person in two natures, divine and human, without confusion, change, division or separation — and split the East in doing it.
Constantinople II
Condemned the Three Chapters and read Chalcedon in Cyril's sense, trying to win back the East it had lost — with a pope held in the city under pressure.
Constantinople III
Against monothelitism: Christ has two wills and two operations, the human freely and always following the divine.
Nicaea II
Ended the first iconoclast crisis: sacred images may be venerated, and the honour paid to them passes to the one they depict.
The Medieval Councils
Held in the Latin West — the Lateran basilica five times, then Lyon, Vienne, Constance and Florence. They legislated for Christendom, ended two schisms, and twice tried to reunite East and West.
Constantinople IV
Deposed Photius and settled the Byzantine patriarchal quarrel — the last council held in the East, and the first the Orthodox do not receive.
Lateran I
The first council held in the West: it ratified the Concordat of Worms and closed the investiture struggle between emperor and pope.
Lateran II
Ended the Anacletan schism and made major orders a diriment impediment to marriage — clerical celibacy as Western law.
Lateran III
Gave the election of a pope to a two-thirds majority of the cardinals alone, and condemned lending at interest.
Lateran IV
The great medieval council: it used the word transubstantiation, and required every Catholic to confess and receive communion once a year.
Lyon I
Deposed the emperor Frederick II and called for the relief of the Holy Land and of the Latin East.
Lyon II
Fixed the rules of the conclave, and made a reunion with the Greeks that their own Church never accepted.
Vienne
Suppressed the Knights Templar under pressure from the French crown, and settled the Franciscan quarrel over poverty.
Constance
Ended the Great Western Schism of three rival claimants and elected Martin V; condemned Wyclif, and burned Jan Hus.
Florence
Defined the papal primacy against conciliarism and signed reunion with the Greeks, Armenians and Copts — undone within years by the fall of Constantinople.
Reformation and Response
Lateran V closed months before Luther posted his theses; Trent answered him. Between the two lies the hinge of Western Christian history.
Lateran V
Legislated a reform of the Roman clergy that was never carried out. It closed in March 1517; Luther posted his theses that October.
Trent
The answer to the Reformation: Scripture and tradition, justification, the seven sacraments, the Mass — and a reform of the clergy that shaped Catholic life for four centuries.
The Modern Councils
Both met in St. Peter's, a century apart. The first defined how the pope teaches; the second described the Church to a world that had stopped listening.
Vatican I
Defined the primacy and the infallibility of the pope, in carefully limited terms — then broke off when Italian troops took Rome.
Vatican II
Sixteen documents on the Church, revelation, the liturgy and the modern world. It defined no new dogma and condemned no one — which is why arguing about it is so easy.
A council is not a parliament and its decrees are not opinions. What an ecumenical council defines with the pope binds the whole Church — which is exactly why it matters to know what each one actually said, and what it left alone.