What the Council of Chalcedon Actually Said in 451 AD

Rev. C•D•F• Warrington, M.Div.
By Rev. C•D•F• Warrington, M.Div.

Ordained Minister, M.Div.

May 16, 2026

2 min read

Oil painting of the Council of Chalcedon bishops assembled in 451 AD with scrolls of the Christological definition in candlelit setting

The Council of Chalcedon convened in October 451 AD, called by Emperor Marcian to resolve the Christological controversies that had fractured the Eastern church since the Council of Ephesus twenty years earlier. Roughly 500 bishops gathered—the largest council of the ancient church—and what they produced would define orthodox Christology for the next fifteen centuries.

The Problem Chalcedon Was Solving

Two competing heresies had created the crisis. Nestorius of Constantinople was accused (fairly or not) of dividing Christ into two persons—one divine, one human—in a way that undermined the unity of the Savior. Eutyches of Constantinople swung to the opposite extreme: he taught that Christ had only one nature, a fused divine-human mixture. Ephesus condemned Nestorius in 431; a subsequent 'Robber Council' in 449 vindicated Eutyches through force rather than argument. Chalcedon corrected both.

The Definition

The Chalcedonian Definition affirmed that Jesus Christ is 'truly God and truly man'—two complete natures, divine and human, united in one person. It drew on Leo I's Tome, which had been read to the council to widespread acclaim. The bishops described the two natures as united 'without confusion, without change, without division, without separation'—four adverbs that became the permanent grammar of orthodox Christology.

Why the Council Was Necessary

Chalcedon was necessary because the wrong Christ saves no one. A divided Christ (Nestorius) cannot be a single Savior. A confused Christ (Eutyches) is neither truly God nor truly man and cannot bridge the gap between them. The real Christ—truly and completely both—is the only one capable of the work the New Testament ascribes to Him.

Frequently Asked Questions

What did the Council of Chalcedon decide in 451 AD?

The Council of Chalcedon defined that Jesus Christ is one Person in two natures — fully divine and fully human — without confusion, change, division, or separation. This became the orthodox definition of the Incarnation accepted by most branches of Christianity.

Why was the Council of Chalcedon necessary?

Conflicting teachings about Christ's nature had divided the church. Nestorius seemed to split Christ into two persons, while Eutyches blended the natures into one. Chalcedon clarified that both natures remain distinct and complete within the one Person of Christ.

Which churches reject the Chalcedonian definition?

The Oriental Orthodox churches — including the Coptic, Ethiopian, Armenian, and Syriac Orthodox — rejected Chalcedon and are sometimes called 'non-Chalcedonian.' Modern ecumenical dialogue has shown that the differences may be more terminological than substantive.

What are the four 'adverbs' of Chalcedon?

Chalcedon defined Christ's two natures as existing 'without confusion, without change, without division, without separation.' These four negatives define what the union of natures is not, ruling out both the merging and the splitting of Christ's divinity and humanity.

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