In view of the length of my previous sermon, I deferred a question of great importance, namely the correct meaning of what John … says in his epistle: "Every spirit that confesses that Jesus Christ has come in the flesh is of God" (1 John 4:2). We see many heresies confessing that Christ came in the flesh, yet we cannot say they are all of God.

The Manichee, of course, denies that Christ came in the flesh. There is no need to linger over this and persuade you at length that such a fallacy is not from God. The Arian, however, professes that Christ came in the flesh, as does the Eunomian, the Sabellian and the Photinian. Why do we seek witnesses to prove them wrong? Who can count the number of these pestilences? For the moment, however, let us deal with the more notorious of these. There are many who do not know the heresies I have mentioned, and they are better off for their ignorance. As we well know, the Donatist says that Christ came in the flesh, and yet far be it that this fallacy is from God. To speak to the more recent heresies, the Pelagians profess that Christ came in the flesh; nevertheless, this fallacy is far removed from God.

Let us then, my beloved ones, reflect carefully. For since we all accept the truth of the words: "Every spirit that confesses that Jesus Christ has come in the flesh is of God," we therefore must refute those who do not profess that Christ came in the flesh. For if we were to allow this confession to stand, we should have to admit that those who profess it are of God. How am I to restrain or deter you from these errors, how am Ito defend you against them with the shield of truth? May the Lord assist me— for your expectation is already a prayer for me—that those may be refuted who do not profess that Christ came in the flesh.

The Arian hears of and preaches the birth by the Virgin Mary. Does he therefore profess that Christ came in the flesh? Not at all! How am Ito prove this? If God will spur on your minds, it will be very easy. What is the question I am posing? I am inquiring whether the Arian professes that Jesus Christ came in the flesh. How can one who denies Christ himself profess that He came in the flesh? Who is Christ, after all? Let us ask the blessed Peter.

When the Gospel was being read just now, you heard how Jesus Christ himself asked, "Who do men say the Son of Man is?" (Matthew 16:13). The disciples gave Him various answers: "Some say, John the Baptist; and others, Elias; and others, Jeremias, or one of the prophets" (v.14). Those who were professing this word or would profess it now, know Jesus Christ as no more than a man. If, however, they know Jesus Christ as no more than a man, they do not know Him at all. If He is only a man and nothing more, then He is not Jesus Christ. But then He asked of the disciples, "But who do you say that lam?" (v. 15). Peter answered for all of them, for there was agreement among all of them. "Thou are the Christ, the Son of the living God" (V. 16).

There you have a true confession and a full confession. You must now reconcile what Christ said of himself with what Peter said of Christ. And what did Christ say of himself? "Who do men say the Son of Man is?" And what did Peter say of Christ? "Thou are the Christ, the Son of the living God." Reconcile these two and you will have the Incarnation of Christ…

What then is the Son of God? Just as we were asking what Christ is and heard that He is the Son of God, let us now ask what the Son of God is. Behold, here is the Son of God: "In the beginning was the Word, and the Word was with God; and the Word was God. He was in the beginning with God. In the beginning was the Word" (John 1:1,2)."In the beginning," as Genesis 1:1 says, "God created the heavens and the earth. You, however, maintain that "In the beginning God created the Word." You say the Word was created and you make the Word a part of Creation. But while you say, "In the beginning God created the Word," the Evangelist says, "In the beginning was the Word." Therefore, "In the beginning God created the heavens and the earth," for He was the Word. "All things were made through Him" (John 1:3). You say the Word was created. If you say it was created, then you deny the Son.

We are seeking the Son according to His nature, not according to grace. We seek the only-begotten Son, not the adopted son. Such is the Son we seek, such is the true Son, "who was by nature God" (Philippians 2:6). I quote the words of the Apostle, lest those of you who are uninstructed think these are my words. We are seeking the Son, "who though he was by nature God," as the Apostle says, "did not consider being equal to God a thing to be clung to." It was not a thing to be clung to, because it was His nature. He obtained it by His nature, not by seizing it. "He did not consider being equal to God a thing to be clung to." He was thus by nature, not by acquisition. Thus He was from all eternity, thus He was co-eternal with the Creator, thus He was equal with the Father; thus He was.

"But he emptied himself." (v. 7). How did He do this? Was it by divesting himself of what He was or by clothing Himself in what He was not? Let us listen to what the Apostle says: "… He emptied himself, taking the nature of a slave" (V. 7). Thus did He empty himself: not by losing His nature as God, but by taking the nature of a slave. His nature as a slave was added to Him, and His nature as God did not depart from Him. This is what it means to profess that Christ came in the flesh. The Arian, however, who does not profess that He is equal with the Father, thus fails to profess Him as the Son. If he does not profess Him as the Son, then he does not profess Christ. How can he who does not profess Christ profess that Christ came in the flesh?

The Eunomian is the equal and the ally of the Arian, differing only in small matters. The Arians are said to have professed that Christ is at least similar to the Father. Although not equal, He is similar. For the Eunomian. however, He is not even similar. Thus he too denies Christ. For if the true Christ is equal with and similar to the Father, then he who denies that He is equal denies also that He is Christ. Thus whoever contends that He is neither equal nor similar denies that Christ came in the flesh. I ask him, "Did Christ come in the flesh?" "He came," he answers. We assume that this is his confession. Then I ask, "Who was this Christ who came in the flesh? Was He equal with the Father or was He unequal?" "Unequal," he answers. Thus you say that one unequal with the Father came in the flesh. In so doing, however, you deny that Christ came in the flesh, for Christ is equal with the Father.

Listen to what the Sabellian says. "He who is the Son is also the Father." This he says, and it is from this that he stings and injects his venom. He says that Christ is the Father. At one moment He is the Son; at the next moment He is the Father, This is not the true Christ. You are mistaken if you say that this is the Christ who came in the flesh. For since this is not Christ, you deny that Christ came in the flesh.

And what do you say, Photinus? He says that Christ is merely a man, that He is not God at all. You profess His nature as a slave and you deny His nature as God. In His nature as God He is equal with the Father; in His nature as a slave He shares in our human lot. Thus you deny that Christ came in the flesh.

And what of the Donatists? Many of the Donatists profess as we do, saying that the Son is equal with the Father and of the same substance. There are other Donatists, however, who, while professing that He is of the same substance as the Father, deny that He is equal with the Father. What need is there to argue with those who deny that He is equal with the Father? If they deny that He is equal, they deny Him also as the Son, and they deny Christ. If they deny Christ, how can they profess that Christ came in the flesh?