Nicaea, First Council of

Nicaea, First Council of,

325, 1st ecumenical council, convened by Roman Emperor Constantine the Great to solve the problems raised by ArianismArianism
, Christian heresy founded by Arius in the 4th cent. It was one of the most widespread and divisive heresies in the history of Christianity. As a priest in Alexandria, Arius taught (c.
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. It has been said that 318 persons attended, but a more likely number is 225, including every Eastern bishop of importance, four Western bishops (among them HosiusHosius
, c.255–c.358, Spanish prelate, bishop of Córdoba, leader against Arianism. He presided at the Council of Nicaea (325) and is credited by Athanasius with having authored the Nicene formulary.
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 of Córdoba, president of the council), and two papal legates. The chief figures at the council were AriusArius
, c.256–336, Libyan theologian, founder of the Arian heresy. A parish priest in Alexandria, he advanced the doctrine famous as Arianism and was excommunicated locally (321).
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 and his opponent, AthanasiusAthanasius, Saint
, c.297–373, patriarch of Alexandria (328–73), Doctor of the Church, great champion of orthodoxy during the Arian crisis of the 4th cent. (see Arianism).
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. The council adopted, as a test of faith, a formula that seems to have been based on a simple baptismal creed presented possibly by Eusebius of Caesarea; this was not, however, the creed generally circulated today as the Nicene Creed (see creedcreed
[Lat. credo=I believe], summary of basic doctrines of faith. The following are historically important Christian creeds.

1 The Nicene Creed, beginning, "I believe in one God the Father Almighty, maker of heaven and earth, and of all things visible and
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). The formula included the Greek word homoousion [consubstantial], which was used concerning the Son and the Father. The word, suggested probably by Hosius, became the touchstone of orthodoxy and the bugbear of Arianism, for it established the divinity and the equality of the Son to the Father. The creed was accepted by all the bishops except two, who were banished along with Arius to Illyricum. The council ruled on other questions as well, attempting to standardize the date of Easter and granting patriarchal authority to the bishop of Alexandria. The First Council of Nicaea was significant as the model and the original of great councils. The test it adopted provided a universal statement of faith in place of the earlier and varying baptismal formulas.