In 325 Constantine agreed with Pope Sylvester to convoke the Council of Nicea between the patriarchs of Rome, Antioch, Alexandria and Constantinople. The Council defined as many of the fundamental tenets of Christian doctrine, notably the Trinitarian belief in the Father creator, the son as the word of God made man, and the Holy Spirit. The Council condemned as heresy those sects who refuse to accept Christ’s double nature as both human and divine, notably the Arians, Nestorians, Syriacs and Copts.
Editors. "Council of Nicea". The Literary Encyclopedia. First published 16 November 2005
[http://www.litencyc.com/php/stopics.php?rec=true&UID=1628, accessed 30 June 2015.]