The Council of Chalcedon Defines Christ's Two Natures, and Splits the Church Doing It
One Person, two natures, unconfused and undivided: a formula the Eastern churches never fully accepted
Quick facts
- Year
- 451 CE
- Rejected views
- Nestorianism (two persons), Eutychianism (one nature)
- Formula
- Two natures, unconfused, unchanged, undivided, unseparated
- Result
- Oriental Orthodox split (Coptic, Ethiopian, others)
What happened
The Fourth Ecumenical Council, meeting at Chalcedon in 451 CE, tried to settle a dispute over how Christ's divine and human natures related to each other, rejecting both Nestorius's teaching of two separate persons in Christ and Eutyches's opposite claim that Christ had only a single, divine nature after the incarnation. The council's Definition of Faith declared Christ to be acknowledged in two natures, without confusion, without change, without division, without separation, united in one person and subsistence while each nature kept its own distinct properties. Large areas of the Christian East, including the Coptic church in Egypt and the church in Ethiopia, rejected this formula and broke communion with Constantinople and Rome, forming what are now called the Oriental Orthodox churches, a division that persists today.
Why it matters
Chalcedon shows that even a council convened specifically to produce unity could instead produce a permanent new division, and the split it caused between Chalcedonian and non-Chalcedonian churches weakened the Byzantine Empire's hold on Egypt and Syria in the centuries before those regions came under Muslim rule.
How we know
The council's Definition of Faith and acts survive in the conciliar record compiled and transmitted through the Greek and Latin manuscript tradition of ecumenical council documents.
Sources
- Internet History Sourcebooks Project, Fordham University. The Council of Chalcedon, Session V, Definition of Faith · Primary source (author-declared)sourcebooks.fordham.edu · Cited as a "primary" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
- Christian History Institute. 451 The Council of Chalcedon · Reputable sourcechristianhistoryinstitute.org · The domain "christianhistoryinstitute.org" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
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Related timelines
- The Byzantine Empire → · The Chalcedonian split weakened Byzantine control over Egypt and Syria; see the Byzantine Empire timeline for how that played out over the following centuries.