Nicene Creed. The 325 AD Council of Nicaea, convened by Emperor Constantine, was the first ecumenical council of the Christian Church, which aimed to unify doctrine and resolve the Arian controversy. Let us pray. I believe in one God, the Father almighty, maker of heaven and earth, of all things visible and invisible. I believe in one Lord Jesus Christ, the Only Begotten Son of God, born of the Father before all ages. God from God, Light from Light, true God from true God, begotten, not made, co