This chapter contains two principal heads: I. A brief exposition of the doctrine of Christ's two natures in one person, sec.1-4. II. A refutation of the heresies of Servetus, which destroy the distinction of natures in Christ, and the eternity of the divine nature of the Son.
1. Proof of two natures in Christ -- a human and a divine. Illustrated by analogy, from the union of body and soul. Illustration applied.
2. Proof from passages of Scripture which distinguish between the two natures. Proof from the communication of properties.
3. Proof from passages showing the union of both natures. A rule to be observed in this discussion.
4. Utility and use of the doctrine concerning the two natures. The Nestorians. The Eutychians. Both justly condemned by the Church.
5. The heresies of Servetus refuted. General answer or sum of the orthodox doctrine concerning Christ. What meant by the hypostatic union. Objections of Servetus to the deity of Christ. Answer.
6. Another objection and answer. A twofold filiation of Christ.
7. Other objections answered.
8. Conclusion of the former objections. Other pestilential heresies of Servetus.
1. When it is said that the Word was made flesh, we must not understand it as if he were either changed into flesh, or confusedly intermingled with flesh, but that he made choice of the Virgin's womb as a temple in which he might dwell. He who was the Son of God became the Son of man, not by confusion of substance, but by unity of person. For we maintain, that the divinity was so conjoined and united with the humanity, that the entire properties of each nature remain entire, and yet the two natures constitute only one Christ. If, in human affairs, any thing analogous to this great mystery can be found, the most apposite similitude  seems to be that of man, who obviously consists of two substances, neither of which however is so intermingled with the other as that both do not retain their own properties. For neither is soul body, nor is body soul. Wherefore that is said separately of the soul which cannot in any way apply to the body; and that, on the other hand, of the body which is altogether inapplicable to the soul; and that, again, of the whole man, which cannot be affirmed without absurdity either of the body or of the soul separately. Lastly, the properties of the soul are transferred to the body, and the properties of the body to the soul, and yet these form only one man, not more than one. Such modes of expression intimate both that there is in man one person formed of two compounds, and that these two different natures constitute one person. Thus the Scriptures speak of Christ. They sometimes attribute to him qualities which should be referred specially to his humanity and sometimes qualities applicable peculiarly to his divinity, and sometimes qualities which embrace both natures, and do not apply specially to either. This combination of a twofold nature in Christ they express so carefully, that they sometimes communicate them with each other, a figure of speech which the ancients termed ijdiwmavtwn koinoniva (a communication of properties).
2. Little dependence could be placed on these statements, were it not proved by numerous passages throughout the sacred volume that none of them is of man's devising. What Christ said of himself, "Before Abraham was I am," (John 8:58), was very foreign to his humanity. I am not unaware of the cavil by which erroneous spirits distort this passage -- viz. that he was before all ages, inasmuch as he was foreknown as the Redeemer, as well in the counsel of the Father as in the minds of believers. But seeing he plainly distinguishes the period of his manifestation from his eternal existence, and professedly founds on his ancient government, to prove his precedence to Abraham, he undoubtedly claims for himself the peculiar attributes of divinity. Paul's assertion that he is "the first-born of every creature," that "he is before all things, and by him all things consist," (Col.1:15, 17); his own declaration, that he had glory with the Father before the world was, and that he worketh together with the Father, are equally inapplicable to man. These and similar properties must be specially assigned to his divinity. Again, his being called the servant of the Father, his being said to grow in stature, and wisdom, and favour with God and man, not to seek his own glory, not to know the last day, not to speak of himself, not to do his own will, his being seen and handled,  apply entirely to his humanity; since, as God, he cannot be in any respect said to grow, works always for himself, knows every thing, does all things after the counsel of his own will, and is incapable of being seen or handled. And yet he not merely ascribes these things separately to his human nature, but applies them to himself as suitable to his office of Mediator. There is a communication of ijdiwvmata, or properties, when Paul says, that God purchased the Church "with his own blood," (Acts 20:28), and that the Jews crucified the Lord of glory (1 Cor.2:8). In like manner, John says, that the Word of God was "handled." God certainly has no blood, suffers not, cannot be touched with hands; but since that Christ, who was true God and true man, shed his blood on the cross for us, the acts which were performed in his human nature are transferred improperly, but not ceaselessly, to his divinity. We have a similar example in the passage where John says that God laid down his life for us (1 John 3:16). Here a property of his humanity is communicated with his other nature. On the other hand, when Christ, still living on the earth, said, "No man has ascended up to heaven but he that came down from heaven, even the Son of man, which is in heaven," (John 3:13), certainly regarded as man in the flesh which he had put on, he was not then in heaven, but inasmuch as he was both God and man, he, on account of the union of a twofold nature, attributed to the one what properly belonged to the other.
3. But, above all, the true substance of Christ is most clearly declared in those passages which comprehend both natures at once. Numbers of these exist in the Gospel of John. What we there read as to his having received power from the Father to forgive sins; as to his quickening whom he will; as to his bestowing righteousness, holiness, and salvation; as to his being appointed judge both of the quick and the dead; as to his being honoured even as the Father,  are not peculiar either to his Godhead or his humanity, but applicable to both. In the same way he is called the Light of the world, the good Shepherd, the only Door, the true Vine. With such prerogatives the Son of God was invested on his manifestation in the flesh, and though he possessed the same with the Father before the world was created, still it was not in the same manner or respect; neither could they be attributed to one who was a man and nothing more. In the same sense we ought to understand the saying of Paul, that at the end Christ shall deliver up "the kingdom to God, even the Father," (1 Cor.15:24). The kingdom of God assuredly had no beginning, and will have no end: but because he was hid under a humble clothing of flesh, and took upon himself the form of a servant, and humbled himself (Phil.2:8), and, laying aside the insignia of majesty, became obedient to the Father; and after undergoing this subjection was at length crowned with glory and honour (Heb.2:7), and exalted to supreme authority, that at his name every knee should bow (Phil.2:10); so at the end he will subject to the Father both the name and the crown of glory, and whatever he received of the Father, that God may be all in all (1 Cor.15:28). For what end were that power and authority given to him, save that the Father might govern us by his hand? In the same sense, also, he is said to sit at the right hand of the Father. But this is only for a time, until we enjoy the immediate presence of his Godhead. And here we cannot excuse the error of some ancient writers, who, by not attending to the office of Mediator, darken the genuine meaning of almost the whole doctrine which we read in the Gospel of John, and entangle themselves in many snares. Let us, therefore, regard it as the key of true interpretation, that those things which refer to the office of Mediator are not spoken of the divine or human nature simply.  Christ, therefore, shall reign until he appear to judge the world, inasmuch as, according to the measure of our feeble capacity, he now connects us with the Father. But when, as partakers of the heavenly glory, we shall see God as he is, then Christ, having accomplished the office of Mediator, shall cease to be the vicegerent of the Father, and will be content with the glory which he possessed before the world was. Nor is the name of Lord specially applicable to the person of Christ in any other respect than in so far as he holds a middle place between God and us. To this effect are the words of Paul, "To us there is but one God, the Father, of whom are all things, and we in him; and one Lord Jesus Christ, by whom are all things, and we by him," (1 Cor.8:6); that is, to the latter a temporary authority has been committed by the Father until his divine majesty shall be beheld face to face. His giving up of the kingdom to the Father, so far from impairing his majesty, will give a brighter manifestation of it. God will then cease to be the head of Christ, and Christ's own Godhead will then shine forth of itself, whereas it is now in a manner veiled.
4. This observation, if the readers apply it properly, will be of no small use in solving a vast number of difficulties. For it is strange how the ignorant, nay, some who are not altogether without learning, are perplexed by these modes of expression which they see applied to Christ, without being properly adapted either to his divinity or his humanity, not considering their accordance with the character in which he was manifested as God and man, and with his office of Mediator. It is very easy to see how beautifully they accord with each other, provided they have a sober interpreter, one who examines these great mysteries with the reverence which is meet. But there is nothing which furious and frantic spirits cannot throw into confusion.  They fasten on the attributes of humanity to destroy his divinity; and, on the other hand, on those of his divinity to destroy his humanity: while those which, spoken conjointly of the two natures, apply to neither, they employ to destroy both. But what else is this than to contend that Christ is not man because he is God, not God because he is man, and neither God nor man because he is both at once. Christ, therefore, as God and man, possessing natures which are united, but not confused, we conclude that he is our Lord and the true Son of God, even according to his humanity, though not by means of his humanity. For we must put far from us the heresy of Nestorius, who, presuming to dissect rather than distinguish between the two natures, devised a double Christ. But we see the Scripture loudly protesting against this, when the name of the Son of God is given to him who is born of a Virgin, and the Virgin herself is called the mother of our Lord (Luke 1:32, 43). We must beware also of the insane fancy of Eutyches, lest, when we would demonstrate the unity of person, we destroy the two natures. The many passages we have already quoted, in which the divinity is distinguished from the humanity, and the many other passages existing throughout Scripture, may well stop the mouth of the most contentious. I will shortly add a few observations, which will still better dispose of this fiction. For the present, one passage will suffice -- Christ would not have called his body a temple (John 2:19), had not the Godhead distinctly dwelt in it. Wherefore, as Nestorius had been justly condemned in the Council of Ephesus, so afterwards was Eutyches in those of Constantinople and Chalcedony, it being not more lawful to confound the two natures of Christ than to divide them.
5. But in our age, also, has arisen a not less fatal monster, Michael Servetus, who for the Son of God has substituted a figment composed of the essence of God, spirit, flesh, and three untreated elements. First, indeed, he denies that Christ is the Son of God, for any other reason than because he was begotten in the womb of the Virgin by the Holy Spirit. The tendency of this crafty device is to make out, by destroying the distinction of the two natures, that Christ is somewhat composed of God and man, and yet is not to be deemed God and man. His aim throughout is to establish, that before Christ was manifested in the flesh there were only shadowy figures in God, the truth or effect of which existed for the first time, when the Word who had been destined to that honour truly began to be the Son of God. We indeed acknowledge that the Mediator who was born of the Virgin is properly the Son of God. And how could the man Christ be a mirror of the inestimable grace of God, had not the dignity been conferred upon him both of being and of being called the only-begotten Son of God? Meanwhile, however, the definition of the Church stands unmoved, that he is accounted the Son of God, because the Word begotten by the Father before all ages assumed human nature by hypostatic union, -- a term used by ancient writers to denote the union which of two natures constitutes one person, and invented to refute the dream of Nestorius, who pretended that the Son of God dwelt in the flesh in such a manner as not to be at the same time man. Servetus calumniously charges us with making the Son of God double, when we say that the eternal Word before he was clothed with flesh was already the Son of God: as if we said anything more than that he was manifested in the flesh. Although he was God before he became man, he did not therefore begin to be a new God. Nor is there any greater absurdity in holding that the Son of God, who by eternal generation ever had the property of being a Son, appeared in the flesh. This is intimated by the angel's word to Mary: "That holy thing which shall be born of thee shall be called the Son of God," (Luke 1:35); as if he had said that the name of Son, which was more obscure under the law, would become celebrated and universally known. Corresponding to this is the passage of Paul, that being now the sons of God by Christ, we "have received the Spirit of adoption, whereby we cry, Abba, Father," (Rom.8:15). Were not also the holy patriarchs of old reckoned among the sons of God? Yea, trusting to this privilege, they invoked God as their Father. But because ever since the only-begotten Son of God came forth into the world, his celestial paternity has been more clearly manifested, Paul assigns this to the kingdom of Christ as its distinguishing feature. We must, however, constantly hold, that God never was a Father to angels and men save in respect of his only-begotten Son: that men, especially, who by their iniquity were rendered hateful to God, are sons by gratuitous adoption, because he is a Son by nature. Nor is there anything in the assertion of Servetus, that this depends on the filiation which God had decreed with himself. Here we deal not with figures, as expiation by the blood of beasts was shown to be; but since they could not be the sons of God in reality, unless their adoption was founded in the head, it is against all reason to deprive the head of that which is common to the members. I go farther: since the Scripture gives the name of sons of God to the angels, whose great dignity in this respect depended not on the future redemption, Christ must in order take precedence of them that he may reconcile the Father to them. I will again briefly repeat and add the same thing concerning the human race. Since angels as well as men were at first created on the condition that God should be the common Father of both; if it is true, as Paul says, that Christ always was the head, "the first-born of every creature -- that in all things he might have the pre-eminence," (Col.1:15, 18), I think I may legitimately infer, that he existed as the Son of God before the creation of the world.
6. But if his filiation (if I may so express it) had a beginning at the time when he was manifested in the flesh, it follows that he was a Son in respect of human nature also. Servetus, and others similarly frenzied, hold that Christ who appeared in the flesh is the Son of God, inasmuch as but for his incarnation he could not have possessed this name. Let them now answer me, whether, according to both natures, and in respect of both, he is a Son? So indeed they prate; but Paul's doctrine is very different. We acknowledge, indeed, that Christ in human nature is called a Son, not like believers by gratuitous adoption merely, but the true, natural, and, therefore, only Son, this being the mark which distinguishes him from all others. Those of us who are regenerated to a new life God honours with the name of sons; the name of true and only-begotten Son he bestows on Christ alone. But how is he an only Son in so great a multitude of brethren, except that he possesses by nature what we acquire by gift? This honour we extend to his whole character of Mediator, so that He who was born of a Virgin, and on the cross offered himself in sacrifice to the Father, is truly and properly the Son of God; but still in respect of his Godhead: as Paul teaches when he says, that he was "separated unto the gospel of God (which he had promised afore by his prophets in the Holy Scriptures), concerning his Son Jesus Christ our Lord, which was made of the seed of David according to the flesh; and declared to be the Son of God with power," (Rom.1:1-4). When distinctly calling him the Son of David according to the flesh, why should he also say that he was "declared to be the Son of God," if he meant not to intimate, that this depended on something else than his incarnation? For in the same sense in which he elsewhere says, that "though he was crucified through weakness, yet he liveth by the power of God," (2 Cor.13:4), so he now draws a distinction between the two natures. They must certainly admit, that as on account of his mother he is called the Son of David, so, on account of his Father, he is the Son of God, and that in some respect differing from his human nature. The Scripture gives him both names, calling him at one time the Son of God, at another the Son of Man. As to the latter, there can be no question that he is called a Son in accordance with the phraseology of the Hebrew language, because he is of the offspring of Adam. On the other hand, I maintain that he is called a Son on account of his Godhead and eternal essence, because it is no less congruous to refer to his divine nature his being called the Son of God, than to refer to his human nature his being called the Son of Man. In fine, in the passage which I have quoted, Paul does not mean, that he who according to the flesh was begotten of the seed of David, was declared to be the Son of God in any other sense than he elsewhere teaches that Christ, who descended of the Jews according to the flesh, is "over all, God blessed for ever," (Rom.9:5). But if in both passages the distinction of two natures is pointed out, how can it be denied, that he who according to the flesh is the Son of Man, is also in respect of his divine nature the Son of God?
7. They indeed find a blustering defence of their heresy in its being said, that "God spared not his own Son," and in the communication of the angel, that He who was to be born of the Virgin should be called the "Son of the Highest," (Rom.8:32; Luke 1:32). But before pluming themselves on this futile objection, let them for a little consider with us what weight there is in their argument. If it is legitimately concluded, that at conception he began to be the Son of God, because he who has been conceived is called a Son, it will follow, that he began to be the Word after his manifestation in the flesh, because John declares, that the Word of life of which he spoke was that which "our hands have handled," (1 John 1:1). In like manner we read in the prophet, "Thou, Bethlehem Ephratah, though thou be little among the thousands of Israel, yet out of thee shall he come forth that is to be a ruler in Israel; whose goings forth have been from of old, from everlasting," (Mic.5:2). How will they be forced to interpret if they will follow such a method of arguing? I have declared that we by no means assent to Nestorius, who imagined a twofold Christ, when we maintain that Christ, by means of brotherly union, made us sons of God with himself, because in the flesh, which he took from us, he is the only-begotten Son of God. And Augustine wisely reminds us,  that he is a bright mirror of the wonderful and singular grace of God, because as man he obtained honour which he could not merit. With this distinction, therefore, according to the flesh, was Christ honoured even from the womb -- viz. to be the Son of God. Still, in the unity of person we are not to imagine any intermixture which takes away from the Godhead what is peculiar to it. Nor is it more absurd that the eternal Word of God and Christ, uniting the two natures in one person, should in different ways be called the Son of God, than that he should in various respects be called at one time the Son of God, at another the Son of Man. Nor are we more embarrassed by another cavil of Servetus -- viz. that Christ, before he appeared in the flesh, is nowhere called the Son of God, except under a figure. For though the description of him was then more obscure, yet it has already been clearly proved, that he was not otherwise the eternal God, than as he was the Word begotten of the eternal Father. Nor is the name applicable to the office of Mediator which he undertook, except in that he was God manifest in the flesh. Nor would God have thus from the beginning been called a Father, had there not been even then a mutual relation to the Son, "of whom the whole family in heaven and earth is named," (Eph.3:15). Hence it is easy to infer, that under the Law and the Prophets he was the Son of God before this name was celebrated in the Church. But if we are to dispute about the word merely, Solomon, speaking of the incomprehensibility of God, affirms that his Son is like himself, incomprehensible: "What is his name, and what is his Son's name, if thou canst tell?" (Prov.30:4). I am well aware that with the contentious this passage will not have sufficient weight; nor do I found much upon it, except as showing the malignant cavils of those who affirm that Christ is the Son of God only in so far as he became man. We may add, that all the most ancient writers, with one mouth and consent, testified the same thing so plainly, that the effrontery is no less ridiculous than detestable, which dares to oppose us with Irenaeus and Tertullian, both of whom acknowledge that He who was afterwards visibly manifested was the invisible Son of God. 
8. But although Servetus heaped together a number of horrid dogmas, to which, perhaps, others would not subscribe, you will find, that all who refuse to acknowledge the Son of God except in the flesh, are obliged, when urged more closely, to admit that he was a Son, for no other reason than because he was conceived in the womb of the Virgin by the Holy Spirit; just like the absurdity of the ancient Manichees, that the soul of man was derived by transfusion from God, from its being said, that he breathed into Adam's nostrils the breath of life (Gen.2:7). For they lay such stress on the name of Son that they leave no distinction between the natures, but babblingly maintain that the man Christ is the Son of God, because, according to his human nature, he was begotten of God. Thus, the eternal generation of Wisdom, celebrated by Solomon (Prov.8:22, seq). is destroyed, and no kind of Godhead exists in the Mediator: or a phantom is substituted instead of a man. The grosser delusions of Servetus, by which he imposed upon himself and some others, it were useful to refute, that pious readers might be warned by the example, to confine themselves within the bounds of soberness and modesty: however, I deem it superfluous here, as I have already done it in a special treatise.  The whole comes to this, that the Son of God was from the beginning an idea, and was even then a preordained man, who was to be the essential image of God. nor does he acknowledge any other word of God except in external splendour. The generation he interprets to mean, that from the beginning a purpose of generating the Son was begotten in God, and that this purpose extended itself by act to creation. Meanwhile, he confounds the Spirit with the Word, saying that God arranged the invisible Word and Spirit into flesh and soul. In short, in his view the typifying of Christ occupies the place of generation; but he says, that he who was then in appearance a shadowy Son, was at length begotten by the Word, to which he attributes a generating power. From this it will follow, that dogs and swine are not less sons of God, because created of the original seed of the Divine Word. But although he compounds Christ of three untreated elements, that he may be begotten of the essence of God, he pretends that he is the first-born among the creatures, in such a sense that, according to their degree, stones have the same essential divinity. But lest he should seem to strip Christ of his Deity, he admits that his flesh is oJmoouvsion, of the same substance with God, and that the Word was made man, by the conversion of flesh into Deity. Thus, while he cannot comprehend that Christ was the Son of God, until his flesh came forth from the essence of God and was converted into Deity, he reduces the eternal personality (hypostasis) of the Word to nothing, and robs us of the Son of David, who was the promised Redeemer. It is true, he repeatedly declares that the Son was begotten of God by knowledge and predestination, but that he was at length made man out of that matter which, from the beginning, shone with God in the three elements, and afterwards appeared in the first light of the world, in the cloud and pillar of fire. How shamefully inconsistent with himself he ever and anon becomes, it were too tedious to relate. From this brief account sound readers will gather, that by the subtle ambiguities of this infatuated man, the hope of salvation was utterly extinguished. For if the flesh were the Godhead itself, it would cease to be its temple. Now, the only Redeemer we can have is He who being begotten of the seed of Abraham and David according to the flesh, truly became man. But he erroneously insists on the expression of John, "The Word was made flesh." As these words refute the heresy of Nestorius, so they give no countenance to the impious fiction of which Eutyches was the inventor, since all that the Evangelist intended was to assert a unity of person in two natures.
 Augustine employs the same similitude, Epist. 52.  John 1:29; 5:21--23; 9:5; 10:9--11; 15:1.  VideCalv. Epist. ad Polonos adversus Stancarum.  See August. in Enchir. ad Laurent. c. 36.  See August. De Corruptione et Gratia. cap. 11, et De Civitate Dei, lib. 10 cap 29, et alibi See also cap. 17 s. 1.  See Irenæus, lib. 4 cap 14 et 37; Tertullian adversus Praxeam. The above passages from The Proverbs is quoted by Augustine, Ep 49, Quæs. 5.  Vide Calv. Defensio Orthodoxæ Fidei Sacræ Trinitatis adversus Prodigiosos Errores Michaelis Serveti Hispani.
 John 1:29; 5:21--23; 9:5; 10:9--11; 15:1.
 VideCalv. Epist. ad Polonos adversus Stancarum.
 See August. in Enchir. ad Laurent. c. 36.
 See August. De Corruptione et Gratia. cap. 11, et De Civitate Dei, lib. 10 cap 29, et alibi See also cap. 17 s. 1.
 See Irenæus, lib. 4 cap 14 et 37; Tertullian adversus Praxeam. The above passages from The Proverbs is quoted by Augustine, Ep 49, Quæs. 5.
 Vide Calv. Defensio Orthodoxæ Fidei Sacræ Trinitatis adversus Prodigiosos Errores Michaelis Serveti Hispani.