Nicene Creed
The Nicene Creed was composed at the First Council of Nicaea (325) to refute Arianism, which denied the full divinity of the Son. It was expanded at the First Council of Constantinople (381) to add fuller teaching on the Holy Spirit. The 381 version is the one universally used in Christian worship. The Western church later added the filioque ("and the Son") to the clause on the Spirit's procession — a major point of contention with the Eastern church.
But to us there is but one God, the Father, of whom are all things, and we in him; and one Lord Jesus Christ, by whom are all things, and we by him. — 1 Corinthians 8:6
Niceno-Constantinopolitan Creed (381 AD)
The form used in Christian worship worldwide.
I believe in one God, the Father Almighty, Maker of heaven and earth, and of all things visible and invisible. (Deut. 6:4; Gen. 1:1; Col. 1:16)
And in one Lord Jesus Christ, the only-begotten Son of God, begotten of the Father before all worlds; God of God, Light of Light, very God of very God; begotten, not made, being of one substance (homoousios) with the Father, by whom all things were made. (John 1:1–3; John 1:14; Heb. 1:3; Col. 2:9)
Who, for us men and for our salvation, came down from heaven, and was incarnate by the Holy Spirit of the virgin Mary, and was made man; (John 6:38; Luke 1:35; Gal. 4:4; Phil. 2:7)
and was crucified also for us under Pontius Pilate; he suffered and was buried; (1 Cor. 15:3; Isa. 53:5)
and the third day he rose again, according to the Scriptures; (1 Cor. 15:4; Acts 10:40)
and ascended into heaven, and sits on the right hand of the Father; (Ps. 110:1; Acts 2:33)
and he shall come again, with glory, to judge the quick and the dead; whose kingdom shall have no end. (Acts 17:31; Luke 1:33)
And I believe in the Holy Ghost, the Lord and Giver of Life; who proceeds from the Father [and the Son — filioque, Western addition]; who with the Father and the Son together is worshipped and glorified; who spoke by the prophets. (John 15:26; John 14:26; 2 Pet. 1:21)
And I believe one holy catholic and apostolic Church. I acknowledge one baptism for the remission of sins; and I look for the resurrection of the dead, and the life of the world to come. Amen. (Eph. 4:4–6; Acts 2:38; 1 Cor. 15:52; John 17:3)
Original Nicene Creed (325 AD)
The original 325 creed was shorter and focused specifically on combating Arius' teaching that the Son was a created being ("there was a time when he was not"). It ended with an explicit anathema against Arian positions. The key phrase added was homoousios — of the same substance as the Father.
We believe in one God, the Father Almighty, maker of all things visible and invisible. And in one Lord Jesus Christ, the Son of God, begotten of the Father, the only-begotten; that is, of the essence of the Father, God of God, Light of Light, very God of very God, begotten, not made, consubstantial with the Father; (John 1:1) by whom all things were made both in heaven and on earth; who for us men, and for our salvation, came down and was incarnate and was made man; he suffered, and the third day he rose again, ascended into heaven; from thence he shall come to judge the quick and the dead. And in the Holy Ghost.
The Homoousios Controversy
The word homoousios ("same substance") was the critical term at Nicaea. Arius had taught that the Son was the greatest of all created beings — exalted, but not eternal and not truly God. Athanasius and the Nicene fathers insisted that a merely created Savior could not accomplish what Romans 5:10 promises, and that only one who truly shares the divine nature can reconcile us to God (2 Pet. 1:4).