7 Again, how glorious a victory for our faith is that in which Ebion— in other words, Photinus— both wins the day and loses it! He castigates Sabellius for denying that the Son of God is Man, and in his turn has to submit to the reproaches of Arian fanatics for failing to see that this Man is the Son of God. Against Sabellius he calls the Gospels to his aid, with their evidence concerning the Son of Mary; Arius deprives him of this ally by proving that the Gospels make Christ something more than the Son of Mary.
Sabellius denies that there is a Son of God; against him Photinus elevates man to the place of Son. Photinus will hear nothing of a Son born before the worlds; against him, Arius denies that the only birth of the Son of God was His human birth. Let them defeat one another to their hearts' content, for every victory which each of them wins is balanced by a defeat. Our present adversaries are ranted in the matter of the Divine nature of the Son; Sabellius in the matter of the Son's revealed existence; Photinus is convicted of ignorance, or else of falsehood, in his denial of the Son's birth before the worlds.
Meanwhile the Church, whose faith is based upon the teaching of Evangelists and Apostles, holds fast, against Sabellius, her assertion that the Son exists; against Arius, that He is God by nature; against Photinus, that He created the universe. And she is the more convinced of her faith, in that they cannot combine to contradict it. For Sabellius points to the works of Christ in proof of the Divinity of Him Who wrought them, though he knows not that the Son was their Author. The Arians grant Him the name of Son, though they confess not that the true nature of God dwelt in Him.
Photinus maintains His manhood, though in maintaining it he forgets that Christ was born as God before the worlds. Thus, in their several assertions and denials, there are points in which each heresy is in the right in defence or attack; and the result of their conflicts is that the truth of our confession is brought into clearer light.
Source: On the Trinity (New Advent)