We have only a
piecemeal knowledge about the use of the term homoousios
(consubstantial) before 325. It first appears in Gnostic writings of the second
century, where it communicates a kind of emanation of one divine being from another,
with the derived deity possessing part of the divinity from which it
emanated. This reflects a conception of God foreign to Christian faith and plainly
was not acceptable to describe the relationship between the Father and the Son
as found in the Scriptures. In the third century, homoousios was used
positively on occasion to describe the relationship between the Father and the
Son—that the Son was homoousios with the Father. In general, when used
positively, homoousios tended to communicate the sense of “the same
order of being.” But at the same time, the term was condemned at the Council of
Antioch in 268. The exact reason for this condemnation is unclear, but it was
probably condemned as communicating a kind of materialistic emanation of the Son
from the Father—the idea that the Son possessed part of the Father’s
being. Thus, before 325 the term homoousios itself had a mixed heritage
in the Christian tradition. (Jared Ortiz and Daniel A. Keating, The Nicene Creed:
A Scriptural, Historical and Theological Commentary [Grand Rapids, Mich.:
Baker Academic, 2024], 92)