First Ecumenical Council
First Council of Nicaea
325 · Nicaea, Bithynia · convened under Constantine I
Historical context
Convened to address the teaching of Arius, who held that the Son was a creature made by the Father.
Major decisions
- Defined the Son as homoousios (consubstantial) with the Father.
- Issued the original Nicene Creed.
- Set a common method for calculating the date of Pascha (Easter).
Canons
20 disciplinary canons addressing clergy, baptism, and church order.
Long-term impact
Established conciliar authority and the dogmatic vocabulary of the Trinity.