Constituted by bishops and other ranking ecclesiastics, these early assemblies legislated matters of both doctrine and discipline. Among the most important of these councils were the Council of Nicea I (325) which ruled on Arianism, the Council of Chalcedon (451) which set down the orthodox teaching on the person and nature of Christ, and the Council of Constantinople I (381) which reaffirmed the teaching of the Council of Nicea I (325). The last of these seven councils was held in 787.