At times like this we need to remind ourselves of what we believe. I am aware that the Ultramontanist will have Calvin, and the ultracalvinist hate the Thomists and consider the Pope an Antichrist — which some popes have been. No office has been without turncoats and traitors, over time. This is a false controversy, for Calvin is here summarizing the orthodox position: that Christ was fully God and fully man. This is a place where ideas matter, and careful thought is required.
For moving too far from reason and the scripture will lead you to error, as Matt Briggs reminds us in his excellent series of extracts from Aquinas’ Summa.
13 Similarly, also, the notion that all sins are equal seems to have some reasonableness, since sin occurs in human acts solely because a person overlooks the rule of reason. But a man who departs a little from reason overlooks its rule, just as one who misses it by a wide margin. So, it would seem that a sin is equal whether the wrong done was small or great.
14 Now, support for this argument seems to come from the practice in human courts of law. In fact, if a boundary line is set up which a certain man is not to cross, it makes no difference to the judge whether he trespassed for a large distance or a small one; just as it is unimportant, when a fighter goes over the ropes, whether he goes very far. So, in the case of a man overstepping the rule of reason, it makes no difference whether he bypasses it a little or a great deal.
15 However, if one takes a more careful look at it, in all matters in which the perfect and the good consists in some sort of commensuration, the greater the departure from the proper measurement, the worse will it be.
Thus, health consists in a properly measured amount of humors, and beauty in a due proportion of bodily members, while truth lies in a measured relation of the understanding, or of speech, to the thing. Now, clearly, the more inequality there is in the humors, the greater the sickness; and the greater the disorder in the members of the body, the greater is the ugliness; and the farther one departs from the truth, the greater is the falsity.
Summa Theologiae, Thomas Aquinas
Are there differences in the Reformed position on the Godhead of Christ and the need for the Cross and atonement? In substance, no. In detail, generally no. There are significant difference in the consideration of tradition and canon law. In the sacraments, and in many things. But Christ calls his faithful through the church, which contains people from all the visible congregations, though many within such are not of the Church invisible.
The functional unity is those who are on their Knees before the cross compared with those who are promethian, considering themselves God. Now that is out the way, let’s have some doctrine.
12. The divinity of Christ, if judged by the works which are ascribed to him in Scripture, becomes still more evident. When he said of himself, “My Father worketh hitherto, and I work,” the Jews, though most dull in regard to his other sayings, perceived that he was laying claim to divine power. And, therefore, as John relates (John 5:17), they sought the more to kill him, because he not only broke the Sabbath, but also said that God was his Father, making himself equal with God. What, then, will be our stupidity if we do not perceive from the same passage that his divinity is plainly instructed? To govern the world by his power and providence, and regulate all things by an energy inherent in himself (this an Apostle ascribes to him, Heb. 1:3), surely belongs to none but the Creator. Nor does he merely share the government of the world with the Father, but also each of the other offices, which cannot be communicated to creatures. The Lord proclaims by his prophets “I, even I, am he that blotteth out thy transgressions for mine own sake,” (Is. 43:25). When, in accordance with this declaration, the Jews thought that injustice was done to God when Christ forgave sins, he not only asserted, in distinct terms, that this power belonged to him, but also proved it by a miracle (Mt. 9:6). We thus see that he possessed in himself not the ministry of forgiving sins, but the inherent power which the Lord declares he will not give to another. What! Is it not the province of God alone to penetrate and interrogate the secret thoughts of the heart? But Christ also had this power, and therefore we infer that Christ is God.
13. How clearly and transparently does this appear in his miracles? I admit that similar and equal miracles were performed by the prophets and apostles; but there is this very essential difference, that they dispensed the gifts of God as his ministers, whereas he exerted his own inherent might. Sometimes, indeed, he used prayer, that he might ascribe glory to the Father, but we see that for the most part his own proper power is displayed. And how should not he be the true author of miracles, who, of his own authority, commissions others to perform them? For the Evangelist relates that he gave power to the apostles to cast out devils, cure the lepers, raise the dead, &c. And they, by the mode in which they performed this ministry, showed plainly that their whole power was derived from Christ. “In the name of Jesus Christ of Nazareth,” says Peter (Acts 3:6), “rise up and walk.” It is not surprising, then, that Christ appealed to his miracles in order to subdue the unbelief of the Jews, inasmuch as these were performed by his own energy, and therefore bore the most ample testimony to his divinity.
Again, if out of God there is no salvation, no righteousness, no life, Christ, having all these in himself, is certainly God. Let no one object that life or salvation is transfused into him by God. For it is said not that he received, but that he himself is salvation. And if there is none good but God, how could a mere man be pure, how could he be, I say not good and just, but goodness and justice? Then what shall we say to the testimony of the Evangelist, that from the very beginning of the creation “in him was life, and this life was the light of men?” Trusting to such proofs, we can boldly put our hope and faith in him, though we know it is blasphemous impiety to confide in any creature. “Ye believe in God,” says he, “believe also in me,” (John 14:1). And so Paul (Rom. 10:11, and 15:12) interprets two passages of Isaiah “Whose believeth in him shall not be confounded,” (Isa. 28:16); and, “In that day there shall be a root of Jesse, which shall stand for an ensign of the people; to it shall the Gentiles seek,” (Isa. 11:10). But why adduce more passages of Scripture on this head, when we so often meet with the expression, “He that believeth in me has eternal life?”
Again, the prayer of faith is addressed to him–prayer, which specially belongs to the divine majesty, if anything so belongs. For the Prophet Joel says, “And it shall come to pass, that whosoever shall call on the name of the Lord (Jehovah) shall be delivered” (Joel 2:32). And another says, “The name of the Lord (Jehovah) is a strong tower; the righteous runneth into it and is safe,” (Prov. 18:10). But the name of Christ is invoked for salvation, and therefore it follows that he is Jehovah. Moreover, we have an example of invocation in Stephen, when he said, “Lord Jesus, receive my spirit;” and thereafter in the whole Church, when Ananias says in the same book, “Lord, I have heard by many of this man, how much evil he has done to thy saints at Jerusalem; and here he has authority from the chief priests to bind all that call on thy name,” (Acts 9:13, 14). And to make it more clearly understood that in Christ dwelt the whole fulness of the Godhead bodily, the Apostle declares that the only doctrine which he professed to the Corinthians, the only doctrine which he taught, was the knowledge of Christ (1 Cor. 2:2). Consider what kind of thing it is, and how great, that the name of the Son alone is preached to us, though God command us to glory only in the knowledge of himself (Jer. 9:24). Who will dare to maintain that he, whom to know forms our only ground of glorying, is a mere creature? To this we may add, that the salutations prefixed to the Epistles of Paul pray for the same blessings from the Son as from the Father. By this we are taught, not only that the blessings which our heavenly Father bestows come to us through his intercession, but that by a partnership in power, the Son himself is their author. This practical knowledge is doubtless surer and more solid than any idle speculation. For the pious soul has the best view of God, and may almost be said to handle him, when it feels that it is quickened, enlightened, saved, justified, and sanctified by him.
Institutes of the Christian Religion Book 1 Chapter 13 paragraphs 12, 13. John Calvin. 15