Chalcedon, Council of - The Fourth Ecumenical Council, held in 451, from 8 October until 1 November inclusive, at Chalcedon, a city of Bithynia in Asia Minor.
Constantinople, First Ecumenical Council of - Called in May, 381, by Emperor Theodosius, to provide for a Catholic succession in the patriarchal See of Constantinople, to confirm the Nicene Faith, to reconcile the semi-Arians with the Church, and to put an end to the Macedonian heresy.
Nicaea, First Council of - First Ecumenical Council of the Catholic Church, held in 325 on the occasion of the heresy of Arius. It defined the Nicene Creed.
The Seven Ecumenical Councils of the Undivided Church - Translation and introduction by Philip Schaff and Henry Wace. Volume XIV: A Select Library of The Nicene and Post-Nicene Fathers of the Christian Church, Second Series. From Christian Classics Ethereal Library.