1st ecumenical council; i.e. convocation of bishops from the whole church
Prior council: none
Summoned by: Emperor Constantine I (306-337) who attended some sessions.
Why: To quell growing unrest in the Greek-speaking East due to the ‘Arian controversy’; i.e. the exact nature of the relationship between the Father and the Son. The conventional belief, as affirmed by the then Patriarch of Alexandria, St. Alexander (313-326), was that the Father and the Son were of the same ‘substance’. Arius, an influential Alexandrian theologian, maintained, however, that Jesus was but of a similar ‘substance’ to God the Father. [‘Arian’ and ‘Arianism’ relate to this Arius, who died in 336, aged 80+.]
Location: Nicaea (now Iznik), Turkey – S. of Constantinople across the Sea of Mamara — close to the then location of the Emperor’s summer residence.
Invitees: All ‘1800’ bishops of the entire Church; ~1000 from the east. Travel costs to/from Nicaea were to be reimbursed, and each bishop could bring two priests and three deacons.
Attendees: Between 250 and 318 bishops, but supposedly only 5 from Latin-speaking (i.e. Western) regions. The Patriarchs of Alexandria, Antioch and Jerusalem were there, as was Arius and the renowned Church historian, Eusebius, the Bishop of Caesarea (Palestine), originally a supporter of Arius – who counted 249 other bishops at Nicaea. (Others said 270 to 318.)
Papal participation: Silvester I, citing old age, did not attend and was represented by two priests and possibly also indirectly by Hosius, Bishop of Cordoba (Spain) – who presided over the council, though from the Latin camp.
Dates: Opened May 20. Nicene Creed approved June 19. Ended July 25, 325.
Key agenda items: Arian controversy; when to celebrate Easter; terms for readmitting those that lapsed during the persecution (i.e. Meletian controversy) and the validity of baptisms by those since deemed ‘heretics’.
Major resolutions: The adoption of the original “We believe in one God, …” Nicene Creed, with Arianism resoundingly rejected in favor of the Father and Son being equal. To always celebrate Easter on a Sunday, independent of the Jewish Passover, across the Church with Alexandria to determine the dating mechanism. Tolerance for the lapsed; counter to Meletians. Invalidity of baptisms performed by Monarchianist. Recognition of the historic stature of Alexandria, Rome and Antioch. ‘Tenure’ and non-transferability of priests; banning of clerical usury and disavowal of self-castration!
Accepted by: All major Christians churches, East and West.
Next council: Constantinople, 381