De Synodis
XII. “If any man hearing that the only Son of God was crucified, says that His divinity suffered corruption or pain or change or diminution or destruction: let him be anathema.”
49. It is clearly shown why the Word, though He was made Flesh, was nevertheless not transformed into Flesh. Though these kinds of suffering affect the infirmity of the flesh, yet God the Word when made Flesh could not change under suffering. Suffering and change are not identical. Suffering of every kind causes all flesh to change through sensitiveness and endurance of pain. But the Word that was made Flesh, although He made Himself subject to suffering, was nevertheless unchanged by the liability to suffer. For He was able to suffer, and yet the Word was not possible. Possibility denotes a nature that is weak; but suffering in itself is the endurance of pains inflicted, and since the Godhead is immutable and yet the Word was made Flesh, such pains found in Him a material which they could affect though the Person of the Word had no infirmity or possibility. And so when He suffered His Nature remained immutable because like His Father, His Person is of an impassible essence, though it is born.
XIII. If any man says Let us make man was not spoken by the Father to the Son, but by God to Himself: let him be anathema.
XIV. If any man says that the Son did not appear to Abraham, but the Unborn God, or a part of Him: let him be anathema.
XV. If any man says that the Son did not wrestle with Jacob as a man, but the Unborn God, or a part of Him: let him be anathema.
XVI. “If any man does not understand The Lord rained from the Lord to be spoken of the Father and the Son, but says that the Father rained from Himself: let him be anathema. For the Lord the Son rained from the Lord the Father.”
50. These points had to be inserted into the creed because Photinus, against whom the synod was held, denied them. They were inserted lest any one should dare to assert that the Son of God did not exist before the Son of the Virgin, and should attach to the Unborn God with the foolish perversity of an insane heresy all the above passages which refer to the Son of God, and while applying them to the Father, deny the Person of the Son. The clearness of these statements absolves us from the necessity of interpreting them.
XVII. “If any man says that the Lord and the Lord, the Father and the Son, are two Gods because of the aforesaid words: let him be anathema. For we do not make the Son the equal or peer of the Father, but understand the Son to be subject. For He did not come down to Sodom without the Father's will, nor rain from Himself but from the Lord, to wit, by the Father's authority; nor does He sit at the Father's right hand by His own authority, but because He hears the Father saying, Sit on My right hand.”
51. The foregoing and the following statements utterly remove any ground for suspecting that this definition asserts a diversity of different deities in the Lord and the Lord. No comparison is made because it was seen to be impious to say that there are two Gods: not that they refrain from making the Son equal and peer of the Father in order to deny that He is God. For, since he is anathema who denies that Christ is God, it is not on that score that it is profane to speak of two equal Gods. God is One on account of the true character of His natural essence and because from the Unborn God the Father, who is the one God, the Only-begotten God the Son is born, and draws His divine Being only from God; and since the essence of Him who is begotten is exactly similar to the essence of Him who begot Him, there must be one name for the exactly similar nature. That the Son is not on a level with the Father and is not equal to Him is chiefly shown in the fact that He was subjected to Him to render obedience, in that the Lord rained from the Lord and that the Father did not, as Photinus and Sabellius say, rain from Himself, as the Lord from the Lord; in that He then sat down at the right hand of God when it was told Him to seat Himself; in that He is sent, in that He receives, in that He submits in all things to the will of Him who sent Him. But the subordination of filial love is not a diminution of essence, nor does pious duty cause a degeneration of nature, since in spite of the fact that both the Unborn Father is God and the Only-begotten Son of God is God, God is nevertheless One, and the subjection and dignity of the Son are both taught in that by being called Son He is made subject to that name which because it implies that God is His Father is yet a name which denotes His nature. Having a name which belongs to Him whose Son He is, He is subject to the Father both in service and name; yet in such a way that the subordination of His name bears witness to the true character of His natural and exactly similar essence.
XVIII. “If any man says that the Father and the Son are one Person: let him be anathema.”
52. Sheer perversity calls for no contradiction: and yet the mad frenzy of certain men has been so violent as to dare to predicate one Person with two names.
XIX. “If any man speaking of the Holy Ghost the Paraclete say that He is the Unborn God: let him be anathema.”
53. The further clause makes liable to anathema the predicating Unborn God of the Paraclete. For it is most impious to say that He who was sent by the Son for our consolation is the Unborn God.
XX. “If any man deny that, as the Lord has taught us, the Paraclete is different from the Son; for He said, And the Further shall send you another Comforter, whom I shall ask: let him be anathema.”
54. We remember that the Paraclete was sent by the Son, and at the beginning the creed explained this. But since through the virtue of His nature, which is exactly similar, the Son has frequently called His own works the works of the Father, saying, I do the works of My Father: so when He intended to send the Paraclete, as He often promised, He said sometimes that He was to be sent from the Father, in that He was piously wont to refer all that He did to the Father. And from this the heretics often seize an opportunity of saying that the Son Himself is the Paraclete: while by the fact that He promised to pray that another Comforter should be sent from the Father, He shows the difference between Him who is sent and Him who asked.
XXI. “If any man says that the Holy Spirit is a part of the Father or of the Son: let him be anathema.”
55. The insane frenzy of the heretics, and not any genuine difficulty, rendered it necessary that this should be written. For since the name of Holy Spirit has its own signification, and the Holy Spirit the Paraclete has the office and rank peculiar to His Person, and since the Father and the Son are everywhere declared to be immutable: how could the Holy Spirit be asserted to be a part either of the Father or of the Son? But since this folly is often affirmed amid other follies by godless men, it was needful that the pious should condemn it.
XXII. “If any man says that the Father and the Son and the Holy Spirit are three Gods: let him be anathema.”
56. Since it is contrary to religion to say that there are two Gods, because we remember and declare that nowhere has it been affirmed that there is more than one God: how much more worthy of condemnation is it to name three Gods in the Father, Son, and Holy Ghost? Nevertheless, since heretics say this, Catholics rightly condemn it.
XXIII. “If any man, after the example of the Jews, understand as said for the destruction of the Eternal Only-begotten God, the words, I am the first God, and I am the last God, and beside Me there is no God, which were spoken for the destruction of idols and them that are no gods: let him be anathema.”
Source: On the Councils, or the Faith of the Easterns (New Advent)