Chalcedonian

Chalcedonian refers to adherents of the Chalcedonian Definition, produced at the Fourth Ecumenical Council held in 451 at Chalcedon, near Constantinople. The Definition declares that in the incarnate Word, Jesus Christ exists in two distinct natures, divine and human, without confusion, change, division, or separation, united in one person. It was formulated to settle Christological disputes between those emphasizing a single divine nature and those arguing for a broader two-nature understanding.

Historically, the Chalcedonian Definition became the doctrinal standard for the churches aligned with the Byzantine state and later the Roman Catholic and most Eastern Orthodox churches, as well as many Protestant denominations through the Reformation. It also marked a sharp divergence with non-Chalcedonian churches, often termed Oriental Orthodox, such as the Coptic, Syriac, Armenian, and Ethiopian traditions, which rejected the formula as not accurately expressing the nature of Christ.

In modern usage, the term Chalcedonian is employed to distinguish churches and theologians that accept the Chalcedonian Definition from those that do not. It remains a central reference point in ecumenical dialogues and in assessments of historical Christology, illustrating how late antique theological disputes shaped the structure of Christian communion and doctrine for centuries.