Where Arius's idea came from, the rival error of Modalism, and the apostolic paper trail Nicaea was defending.
Here's the key that unlocks the whole 300-year argument: nearly everyone was trying to protect the same precious truth — "God is one" (monotheism). The heresies weren't villains cackling against God; they were over-corrections. There were two ways to fall off the road.
God is a single person who shows up in three modes or masks: sometimes Father, sometimes Son, sometimes Spirit — never all at once.
"The Father became the Son."
✗ Loses the distinction of the persons
One divine being (oneness preserved), eternally existing as three distinct persons — Father, Son, Spirit — each fully God.
"True God from true God… of the same substance."
✓ Holds both oneness AND distinction
Keep God's oneness by making the Son a creature — the highest one, but created. Distinct persons, but the Son isn't truly God.
"There was when he was not."
✗ Loses the full deity of the Son
Modalism guards oneness by fusing the persons · Arianism guards it by ranking them · Nicaea keeps both.
Before Nicaea ever met, the worship of Christ as God is documented in an unbroken line back to the apostles — including by people who learned from them directly, and even by a hostile outsider:
c. AD 90–100 — The New Testament: "the Word was God" (John 1:1); Thomas to Jesus: "My Lord and my God!" (John 20:28).
c. 107 — Ignatius of Antioch (a disciple of the apostle John) writes of "Jesus Christ our God."
c. 112 — Pliny the Younger, a pagan Roman governor (no stake in it), reports Christians "sang hymns to Christ as to a god."
c. 180–200 — Irenaeus (taught by Polycarp, who was taught by John) and Tertullian, who coins the Latin word trinitas, "Trinity."
So Nicaea (325) didn't invent Christ's deity — it defended language for what the church had worshipped for ~300 years. (Recap of Lesson 2's thread; see Pliny & Ignatius.)
Arius didn't appear from nowhere. His view sits at the end of a strand called subordinationism — the tendency to rank the Son below the Father. You can trace a near-direct teaching line:
So Arianism was a sharpening of an older subordinationist habit. Even some earlier, otherwise-respected writers had used loose language that leaned that way — which is exactly why the church eventually needed a precise word (homoousios) to close the door. (Arianism; Lucian of Antioch.)
While the subordinationists were busy lowering the Son, others over-corrected the other way and fused the persons together. This is Modalism (also called Sabellianism, after its most famous teacher, or Monarchianism). Its own genealogy:
The decisive takedown came from Tertullian (~213) in a book literally titled Against Praxeas. He mocked the logic: if the Father is the Son, then the Father himself suffered and died on the cross. He coined a label for it — Patripassianism ("the Father suffered") — and the absurdity helped sink it.
Tertullian labeled the movement "Patripassianism"… because it implied that the Father suffered on the Cross. — Sabellianism (overview); see also Modalism & Monarchianism
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Want to read a bit of Tertullian's Against Praxeas? Curious how Modalism survives today (some modern groups are basically modalist)? Or how "subordinationism" differs from just saying the Son obeys the Father?
Message me. When you're ready, say next — the natural close to the "Who is Jesus?"
arc is Chalcedon (451): not "is Jesus God?" but "how is he God and man at once?"