Britannica Sources used in this answer

What decisions did the Council of Chalcedon make in 451?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Christology The Transfiguration, the nature of Jesus as the Son of God being revealed to the apostles Peter, James, and John, mosaic icon, early 13th century; in the Louvre, Paris.

The Council of Chalcedon, held in 451, was a pivotal event in the development of Christology. Its primary theological decision was to establish a formal definition of the two natures of Christ, affirming that Jesus is one person who is both "perfect in deity and perfect in humanity" without the two natures being "mixed, transmuted, divided, or separated."12

Key decisions and actions of the council included:

Doctrinal Affirmation: The council approved the Nicene Creed, two letters of St. Cyril of Alexandria emphasizing the unity of Christ, and the Tome of Pope Leo I, which confirmed the existence of two distinct natures in Christ.2
Rejection of Heresies: The council formally condemned Nestorianism and rejected the monophysite doctrine, which erroneously claimed that Christ possessed only a single, divine nature.123
Institutional Governance: Beyond theology, the council issued disciplinary decrees regarding clergy and monks and elevated Jerusalem and Constantinople to the status of patriarchates, contributing to the church's institutional stability.2