What Is Arianism? A Simple Explanation

Arianism is probably the most famous heresy in Christian history. It’s the reason the Council of Nicaea happened. It’s the controversy that gave us the Nicene Creed. And versions of it keep resurfacing, century after century, even among people who have never heard the name “Arius.”

So what is it, actually?

Who Was Arius?

Arius was a priest in Alexandria, Egypt, in the early 4th century. He was popular, charismatic, and — according to his opponents — a gifted songwriter who set his theology to catchy tunes that spread through the streets of Alexandria.

His central concern was protecting God’s uniqueness. If God is truly one, truly supreme, truly without origin or cause — then nothing else can share that status. Not even the Son. His reasoning was tighter than his opponents liked to admit: unbegottenness is not an incidental attribute of God — it is a fundamental, essential one. The Son, by the testimony of Scripture itself, is begotten. If the biblical text is the authority, a begotten being cannot be the unbegotten God.

What Did Arius Actually Teach?

Arius’s argument went something like this:

1. God the Father is the one true God — unbegotten, without origin, eternally self-existent.
2. The Son was brought into being by the Father before all creation. The Son is the first and greatest of all God’s works — through the Son, everything else was made.
3. Therefore, there was a “time” (or at least a logical moment) when the Son did not exist. The Father existed; the Son did not. Then the Father generated the Son.

The famous Arian slogan captured it: “There was when he was not.” The Son had a beginning. The Father didn’t.

This didn’t mean the Son was ordinary. Arius believed Jesus was divine in some sense — exalted far above angels and humans, the agent through whom God created the universe. But the Son was not God in the same way the Father was God. The Son was a creature — the supreme creature, but a creature nonetheless.

Why Did It Matter?

To modern ears, this might sound like a technical distinction. What’s the big deal if Jesus is “very, very divine” rather than “fully divine”?

The answer is salvation.

The church fathers argued that if Jesus is a creature, he can’t save us. Only God can bridge the gap between God and humanity. A created being — however exalted — stands on our side of the divide. Athanasius, Arius’s fiercest opponent, put it bluntly: if the Son is a creature, then when we worship Jesus, we’re worshipping a creature. That’s idolatry.

The counter-argument, then and now, is equally direct: God the Father saves through the Son. The Son doesn’t need to be God to be God’s appointed instrument of salvation. Paul wrote that “there is one mediator between God and men, the man Christ Jesus” (1 Timothy 2:5) — placing the one God and the man Jesus on different sides of the mediation.

There was also a philosophical issue. If the Father created the Son, then God changed — God went from being “not a Father” to being “a Father.” But the Greek philosophical tradition (deeply influential in early Christianity) held that God is immutable, unchanging. A God who creates a Son at some point is a God who changes. That was unacceptable.

What Happened at Nicaea?

In 325, Emperor Constantine convened the Council of Nicaea to resolve the dispute. The council’s answer was a single Greek word: homoousios. The Son is “of one substance” with the Father. Same essence. Co-eternal. Uncreated.

The Nicene Creed, produced at this council, specifically targets Arian claims:

• “Begotten, not made” — the Son’s generation isn’t an act of creation.
• “Of one substance with the Father” — the Son shares the Father’s divine nature completely.
• “True God from true God” — not a lesser divinity, not a superior angel, but God in the fullest sense.

Arius was condemned and exiled.

What Happened After Nicaea?

If you think that settled things, you haven’t read much church history.

The next several decades were chaos. Bishops whom Athanasius labelled “Arian” regrouped — though most of them were not followers of Arius at all but bishops with their own pre-existing convictions about the Son’s relationship to the Father. The label was a polemical weapon, applied by the pro-Nicene party to anyone who rejected homoousios, regardless of their actual theology. Emperors took sides. Athanasius was exiled five times. A series of anti-Nicene councils reversed Nicaea’s decision. For roughly twenty years (360–380), the Nicene position was the minority view, condemned by the institutional church.

It wasn’t until the Council of Constantinople in 381 that the Nicene formula was definitively reaffirmed — and even then, it took the brilliant theological work of the Cappadocian Fathers (Basil, Gregory of Nazianzus, Gregory of Nyssa) to clarify what homoousios actually meant.

Why It Keeps Coming Back

Arianism is the Christian heresy that won’t stay dead. It resurfaces in different forms because its core intuition is genuinely appealing:

Jehovah’s Witnesses teach that Jesus is Michael the Archangel — God’s first creation, through whom all else was made. This is essentially Arianism with different vocabulary.

Casual subordinationism is rampant in everyday Christianity. When believers say things like “Jesus is the Son of God” and mean it the way you’d mean “John is the son of Robert” — an implication of derivation and subordination — they’re closer to Arius than to Nicaea.

The biblical evidence is genuinely ambiguous. Jesus says “the Father is greater than I” (John 14:28). He prays to the Father. He says he doesn’t know the day or hour of his return (Mark 13:32). Paul says the Son will ultimately hand the kingdom back to the Father (1 Corinthians 15:28). Read on their own, these texts sound Arian. The Nicene reading requires synthesizing them with “high” Christological texts like John 1:1 and Philippians 2:6 — a synthesis that isn’t self-evident.

The Bottom Line

Arius wasn’t stupid, and the bishops labelled “Arian” weren’t villains. They were trying to protect monotheism — the foundational claim of both Judaism and Christianity — from what looked like a slide into polytheism. Their concern was genuine, and it persists today among biblical unitarians, who hold that the Father alone is God (1 Corinthians 8:6), that Jesus is God’s human Son and Messiah, and that the subordination texts mean exactly what they say.

The Nicene answer was that you can affirm both strict monotheism and the full divinity of the Son — but only by developing vocabulary (one ousia, three hypostaseis) that the New Testament never uses. The price of “orthodoxy” was moving beyond biblical language into Greek philosophical categories. Whether that move was a legitimate development or an overreach is a question Christians have been arguing about for seventeen centuries. It was settled not by exegesis alone but by a combination of theological argument, imperial power, and the systematic destruction of the losing side’s writings. We have the Nicene case in full; we have the anti-Nicene case almost entirely through the words of its opponents.

And they’re still arguing.

Think you’d have sided with Arius or Athanasius? Take the quiz and find out what the councils would say about your view.