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Know Your Heresies: Sabellianism

One Liam in Three Persons (2010), digital painting by Timothy Lim

The Holy Tri-Neeson (2011), T-shirt graphic by Timothy Lim

Encyclopædia Britannica has more.

The upshot: While we don’t know many of the specifics of the Sabellian heresy, we do know it was a variant of the Modalist heresy. Modalism is, briefly, the notion that the Holy Spirit, the Son, and perhaps — depending on the kind of Modalism in question — the Father, are not essential to God’s Being. Rather (says Modalism), the one God (who may or may not be identical with the Father) is like an actor; the Persons of the Trinity (or, at least, the Holy Spirit and the Son) are like roles the one God plays.

I find that almost all attempts to explain Trinitarianism have to pass through Modalism early on.