The Chalcedonians were called so because they followed the resolutions of the 451 CE Council of Chalcedon. That council accepted Trinitarianism, the idea that one God existed in three divine persons, and they were co-eternal, three distinct persons that shared the same essence. It also accepted that Jesus had two natures, one divine and one human. (This is essentially the Roman Catholic tradition.)
This council rejected Arianism, Nestorianism, and others.
What Justinian did was called the "Three-Chapter Controversy" because it rejected three different ideas/sets of documents that existed:
- The writings of Theodore of Mopsuestia, whose writings included what were considered heresies.
- The letter of Ibas of Edessa, associated with the growth of Nestorianism, and who promoted the idea of Theodore of Mopsuestia.
- Some writings of Theodoret of Cyrus, a 5th-century theological commentator who would not reject Nestorius of Constantinople, and wrote opposing Cyril of Alexandria's attack on Nestorius.
Justinian wanted one universal religion throughout the empire. Opposition/heresy had to be quelled. About 543/44 he issued an edict that rejected the above-mentioned writings, hoping that the eastern bishoprics (who favored them) would accept the Council of Chalcedon and result in religious unity.
There was resistance to the edict, partially because of religious obstinance, partially because the Latin-speaking authorities did not read Greek and could not understand the writings mentioned, and could not therefore discuss them intelligently.
The council called by Justinian to discuss and ratify his edict (to which he sent Belisarius as an emissary) had little effect in the East. More concerned with encroaching Persians than changes in theology, Justinian's dream of a catholic theology throughout his empire failed.
Tomorrow we'll look at the ongoing threat of the Persians.