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First Council of Nicaea

Icon of the First Council of Nicaea.
Nicaea made homoousios the decisive word in the Arian controversy. via Wikimedia Commons · Public domain

A dispute over Jesus was splitting churches across the Roman Empire. Arius taught that the Son of God was the greatest being God had made, but not fully God himself. His opponents believed that Christians worship Jesus precisely because he is truly God. Emperor Constantine gathered bishops at Nicaea to settle the matter. They said the Son is 'of one substance' with the Father—meaning not a creature, but fully God. This was the decisive beginning of the creed many Christians still recite today.

Jesus the Son is fully God, not a created being.

Highlights

  • Constantine summoned the council.
  • Arius was condemned.
  • The bishops said the Son is fully God.
  • The later creed grew from this settlement.

How it happened

What happened

Constantine gathered bishops at Nicaea to answer the Arian controversy and restore unity across the imperial church.

The argument

Arius said the Son was created by the Father. The Nicene party insisted that the Son is fully divine, not the highest creature.

What changed

The council used homoousios to confess that the Son is of one substance with the Father.

Why it matters

If the Son is not truly God, then God himself has not come to save. Nicaea made that line non-negotiable.

People in the story

Constantine the GreatConstantine the GreatFirst Christian Roman emperor. Issued the Edict of Milan (313), convened the Council of Nicaea (325), and was baptized on his deathbed by Eusebius of Nicomedia.Athanasius of AlexandriaAthanasius of AlexandriaBishop of Alexandria and chief defender of Nicene orthodoxy against Arianism. Five times exiled. Wrote On the Incarnation and the Vita Antonii.AriusAriusAlexandrian presbyter whose teaching that the Son was a created being sparked the Arian controversy. Condemned at Nicaea (325). Heretic.
Eusebius, Vita Constantini 3.6-14
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Cover of Eusebius's Ecclesiastical History
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Eusebius of Caesarea

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Today: First Council of Nicaea (325) — Patristic Lineage