Paul of Samosata, bishop of Antioch [was] the first man to use the Greek adjective homoousios (“of the same substance”) to denote the Son’s relation to the Father in the Godhead. The Son, that is to say, was “of the same substance” as the Father in the way in which a stream is “of the same substance” as the foundation from which it flows. It is remarkable that this very adjective, used by Paul of Samosata in a sense judged to be heretical, later became the hallmark of orthodoxy when used in a rather different sense by Athanasius in his struggle against the Arian heresy . . .The phrase “of the same essence (Greek homoousios) as the Father” caused some heart-searching. Not only was it absent from the Bible; it had actually been used by the heretic Paul of Samosata in the previous century to express his conception of Christ as an emanation from God. Many questioned the wisdom of including it in the Creed of Nicaea. It was, however (according to Eusebius), suggested by Constantine himself; and when the Arians showed their dismay at it, the anti-Arian party took it up and insisted that it was indispensable, as no other term could explicitly exclude Arianism. The Arians and their sympathisers would have agreed to describe Christ as “like” (Greek homoios) the Father,” but these terms were naturally judged inadequate to safeguard the catholic belief.
F.F. Bruce, The Spreading Flame: The
Rise and Progress of Christianity from its First Beginnings to the Conversion
of the English, 255, 306.