4 Since, therefore, they cannot make any change in the facts recorded, they bring novel principles and theories of man's device to bear upon them. Sabellius, for instance, makes the Son an extension of the Father, and the faith in this regard a matter of words rather than of reality, for he makes one and the same Person, Son to Himself and also Father. Hebion allows no beginning to the Son of God except from Mary, and represents Him not as first God and then man, but as first man then God; declares that the Virgin did not receive into herself One previously existent, Who had been in the beginning God the Word dwelling with God, but that through the agency of the Word she bore Flesh; the 'Word' meaning in his opinion not the nature of the pre-existent Only-begotten God, but only the sound of an uplifted voice.
Similarly certain teachers of our present day assert that the Image and Wisdom and Power of God was produced out of nothing, and in time. They do this to save God, regarded as Father of the Son, from being lowered to the Son's level. They are fearful lest this birth of the Son from Him should deprive Him of His glory, and therefore come to God's rescue by styling His Son a creature made out of nothing, in order that God may live on in solitary perfection without a Son born of Himself and partaking His nature.
What wonder that their doctrine of the Holy Ghost should be different from ours, when they presume to subject the Giver of that Holy Ghost to creation, and change, and non-existence. Thus do they destroy the consistency and completeness of the mystery of the faith. They break up the absolute unity of God by assigning differences of nature where all is clearly common to Each; they deny the Father by robbing the Son of His true Sonship; they deny the Holy Ghost in their blindness to the facts that we possess Him and that Christ gave Him.
They betray ill-trained souls to ruin by their boast of the logical perfection of their doctrine; they deceive their hearers by emptying terms of their meaning, though the Names remain to witness to the truth. I pass over the pitfalls of other heresies, Valentinian, Marcionite, Manichee and the rest. From time to time they catch the attention of some foolish souls and prove fatal by the very infection of their contact; one plague as destructive as another when once the poison of their teaching has found its way into the hearer's thoughts.
Source: On the Trinity (New Advent)