Sabellianism
In one sentence
A historical form of modalistic monarchianism associated with Sabellius.
In simple terms
Sabellianism explains Father, Son, and Holy Spirit as different manifestations of one divine Person.
Biblical truth
Scripture simultaneously affirms divine unity and portrays real relations among Father, Son, and Spirit.
Key Scriptures
Matt. 3:16–17 · Matt. 28:19 · John 1:1–2 · John 17:5 · John 14:16
Example
In this model Father and Son are not eternal interlocutors within God but denote different modes of divine revelation.
Who holds it
Historically associated with Sabellius and strands of third-century modalistic Monarchianism.
Not to be confused with
Not to be confused with any strong affirmation of divine unity; Nicene Trinitarianism is also strictly monotheistic.
History
The teaching is known largely through opponents, so the precise formulations of Sabellius are only partly reconstructable.
Main point of debate
The dispute concerns whether Father, Son, and Spirit are eternal personal distinctions in God or successive manifestations of one Person.