Which notable doctrine was affirmed at the Council of Chalcedon?

The Council of Chalcedon, held in 451 AD, is particularly known for affirming the doctrine of the duality of Christ, which articulates the belief that Jesus Christ is both fully divine and fully human. This council responded to debates over Christ's nature, specifically the Monophysite controversy, which proposed that Christ has only one divine nature rather than two distinct natures.

The Chalcedonian Definition established that in the one person of Jesus Christ, there are two natures—one divine and one human—united "without confusion, without change, without division, and without separation." This doctrine was pivotal in shaping orthodox Christian belief and distinguishing it from various heretical interpretations regarding Christ's nature.

In contrast, while the other choices address important theological issues, they do not encapsulate the primary affirmation made by the Council of Chalcedon. Monophysitism is the very doctrine that Chalcedon opposed, Trinitarian theology reflects beliefs about the nature of God rather than Christ specifically, and the nature of salvation, though vital to Christian doctrine, was not the central focus of Chalcedon’s decrees. Thus, the duality of Christ stands out as the most significant affirmation made during this ecumenical