God is at all times essentially and actively present in all creatures, Jer. 23, 23. 24; Eph. 4, 10; and to this union with the Triune God all created things owe their subsistence, Acts 17,28; Col. 1, 16—18. This union has been fitly called the general union (unio generalis) because it embraces all existing things, animate and inanimate, rational and irrational, in the entire realm of nature. In addition to this union, Scripture teaches also a special union (unio specialis, unio spiritualis), namely, the most gracious union of the Triune God with the believers (unio mystica), by which the communion of saints is the living, spiritual temple of God, John 14, 23; 1 Cor. 3, 16 f.; 6, 17—19; Eph. 1, 22. 23. In the third place. Holy Scripture teaches a sacramental union (unio sacramentaJis), by which the true body and blood of Christ are really and substantially present in the Lord’s Supper and are distributed and received in, with, and under the bread and wine.
From these unions we distinguish the personal union (unio personalis), by which the divine and the human nature of Christ are most intimately united in the one person of the God-man (hypostatic union, unio hypostatica). Hollaz defines the personal union thus: “The personal union is the conjunction of the two natures, divine and human, subsisting in the one hypostasis (ὑπόστασις, persona) of the Son of God, producing a mutual and indissoluble communion of both natures.” (Doctr . Theol., p. 296.) This personal union was effected when in His incarnation the λόγος so assumed human nature into His divine person (actus unitionis) that in the incarnate Christ (λόγος ἔνσαρκος) God and man are forever one undivided and indivisible person (status unionis, ἕνωσις ὑποοτατική). This is “the mystery of godliness,” of which St. Paul testifies that it is “confessedly great,” ὁμολογουμένως μέγα, 1 Tim. 3, 16, or the miracle of all ages.
The personal union is proved incontrovertibly by the personal propositions (propositions personales), that is, by clear Scripture- passages in which with reference to the incarnate Christ it is said that God is man and man is God. Matt. 16, 13—17: The Son of Man is the Son of the living God; Luke 1, 31. 32: The Son of Mary is the Son of the Highest; Jer. 23, 5. 6: The Branch of David is the Lord, יְהוָה our Righteousness; Rom. 9, 6: The Christ who comes of the fathers is God, blessed forever; John 1,14: The Word was made flesh; Rom. 1, 3. 4: He who was made of the seed of David is God’s Son, our Lord; etc. These personal propositions can be explained only on the ground that the divine and the human nature are so intimately and permanently united in the person of Christ that He is at the same time true God and true man.
The personal, or hypostatic, union of the two natures in Christ is unique; that is to say, in the entire realms of both nature and grace there is no other union of God and man like that which exists in Christ. It may be somewhat illustrated (the union of soul and body in man; iron glowing with fire); but these unions are only similar to, not like, the personal union. Thus, while we can say that in Christ, God is man and man is God, we cannot say that in man the soul is body or that in iron glowing with fire the iron is fire.
For this reason the personal propositions have been called unusual or singular (propositiones inusitatae), or propositions for which there is no analog. Yet, while the personal propositions are inusitatae (unique), they are real and not merely verbal (verbales); proper (propriae), not metaphorical, figurative, or tropical (impropriae et tropicae). That is to say, in Christ the two natures are truly united, just as the personal propositions affirm, so that Christ is God-man (θεάνθρωπος) in the fullest sense of the term (persona σύνϑετος, persona composita).
While on the basis of Scripture the Christian Church teaches the personal union of the two natures in Christ, it emphatically rejects a) the error of Eutyches (monophysitism), who taught that the union was effected by a mingling of the two natures into each other or by confusion or a conversion of the one nature into the other (unio per mixtionem et conversionem), so that by such mingling, or conversion, a third object (tertium quiddam) came into being; b) the error of Nestorius, who, though affirming a connection (συνάφεια) of the two natures, nevertheless regarded them as separate (Formula of Concord: “two boards glued together”), thus denying the personal union and in particular the communion of the natures and the communication of attributes (Mary is not ϑεοτόκος).
Against these two errors the Council of Chalcedon (451) declared: “We confess one and the same Jesus Christ, the Son and Lord only-begotten, in two natures (ἐν δύο φύσεσιν) without mixture (ἀσυγχύτως), without change (ἀτρέπτως), against Eutyches, without division (ἀδιαιρέτως), without separation (ἀδιαιρέτως), against Nestorius.” The error of Nestorius was later championed by Zwingli (ἀλλοίωσις), who taught: Wherever Scripture says that Christ has suffered, you must read: The human nature only has suffered.
In refutation of the Eutychian as well as the Zwinglian (Nestorian) error our dogmaticians say: “The two natures in Christ are united a) inconvertibly (the divine nature was not changed into flesh; against Eutyches), b) unconfusedly (the two natures were not mingled into a third object; against Eutyches), c) inseparably and uninterruptedly (against Nestorius); that is to say, the two natures in Christ are never separated by any intervals either of time or place. The union was neither dissolved in death (time), nor is the λόγος after the incarnation anywhere present outside the flesh (place). After the incarnation the Son of God is always and everywhere Filius Dei incarnatus. Neque caro extra λόγον, πόφιια λόγος extra carnem. John 1, 14; Col. 2, 9; Rom. 5, 10; etc.
a. Not unio nominalis, a nominal union, as though the Son of Man were God only in name (Deus nuncupative). Christ is true and very God, John 10, 30, so that the personal union is real (unio realis). While all Unitarians are willing to call Christ God (Kitschl: “For us Christ has the value of God; hence, while the ascription of deity to Christ is not a real judgment Seinsurteil, it is a value judgment Werturteteil”; Harnack: “Christ may be called the Son of God because He proclaimed to men the fatherhood of God”), they strenuously deny that He is God de facto.
b. Not unio naturalis, a natural union, like that of soul and body, which have been created for each other. The personal union is not a natural union, since it intimately and inseparably unites the Creator and the creature, God and man, into one person (ens increatum et creatum).
This union is therefore incomprehensible to human reason, 1 Tim. 3, 16. To render it somewhat intelligible to the human mind, some scholastic theologians said that the Son of God was joined to human nature through the means of the soul (mediants anima), since only in this way two immaterial beings (God and soul are both spirits) can be joined. The soul, however, is just as much a creature as the body, so that the great problem how Ood could be united with a creature into one person is hereby not solved. But this view is also unscriptural; for while Christ in death gave up His spirit, Matt. 27, 60; Mark 15, 37; John 19, 30, so that the natural union (unio naturalis) of soul and body ceased, the personal union did not cease (Rom. 5, 10: Christ’s death was the death of the Son of God). For this reason the personal union cannot be a natural union, or a union mediante anima.
c. Not unio accidentalis, an accidental union, as when two boards are glued together or a human body is clothed in a garment. An accidental union does not join two things into one in such a manner as the personal union unites the two natures into one person. Of two things accidentally joined together one may be injured and the other not (the garment may be torn, while the body remains unharmed), whereas the human nature in Christ was so joined to the divine that, when the human nature suffered, shed blood, and died, the Son of Ood suffered, shed His blood, and died, 1 John 1, 1. 7; 1 Cor. 2, 8; Acts 20, 28.
d. Not unio sustentativa (nuda παρουσία sive παράστασις), or a sustaining union by mere divine presence, by which God is present in, and sustains, all creatures, Col. 1,17; Acts 17, 28. It is true, the divine nature sustained the human in Christ’s great suffering, Matt. 26, 42; yet the essence of the personal union does not consist in that sustaining act, but rather in the most intimate conjunction of the two natures in the one person of Christ. Creatures are never assumed into the Godhead in spite of the sustaining presence of God; but through the personal union the human nature of Christ was received into the person of the Son of God.
e. Not unio habitualis (relativa, σγετικῆ), a relative union, which indeed places two things into a certain relation with each other, but still leaves them separate essentially. Thus two friends are joined together by the union of mutual love; yet they remain two distinct individuals, separated even by space. But the personal union of the two natures in Christ was not relative (Theodore of Mopsuestia, † ca. 428), since the fulness of the Godhead dwells in Christ bodily, Col. 2, 9. The two natures in Christ are inseparably joined and by their most intimate and permanent union constitute the one indivisible Christ. While the union effected through friendship may cease, the personal union never ceases.
f. Not unio essentialis sive commixtiva, an essential or commingling union, by which through the personal union the two natures coalesced into one nature or essence (Eutychianism).
Since the charge was raised against the Lutherans that they, too, mixed the two natures into each other (conversio aut confusio aut exaequatio), the Formula of Concord expressly refuted this erroneous accusation, saying (Thor. Decl., VIII, 62 f.): “In no way is conversion, confusion, or equalization of the natures in Christ or of their essential properties to be maintained or admitted. Accordingly we have never understood the words realis communi- catio, or communicated realiter, that is, the impartation or communion which occurs in deed and truth, of any physica communicatio vel essentialis transfusio, physical communication or essential transfusion, that is, of an essential, natural communion or effusion, by which the natures would be commingled in their essence, and their essential properties; . . . but we have only opposed them to verbalis communicatio (verbal communication).”
g. Not unio per adoptionem, a union by adoption (Adoptionism; Felix of Urgel, Elipandus of Toledo, in the 8th century; condemned by various synods 792—799, mainly at the instigation of Alcuin, f 804), by which Christ according to His human nature has been said to be God’s adopted Son (Filius Dei adoptivus). Adoptionism is a form of Nestorianism and presupposes two persons in Christ, one divine and the other human, of whom the latter was divinely adopted. In opposition to this error our Lutheran dogmaticians teach that Christ according to His human nature is the “born Son of God,” or the Son of God by His very birth (Filius Dei natus vel ab ipsa nativitate). The incarnation was not an adoption of a human person by God, but the assumption of human nature into the person of the λόγος.
Eutychianism and Nestorianism (Zwinglianism) are attempts to render the mystery of the incarnation intelligible to human reason, either by mingling or by separating the two natures. But both errors, which equally annul the personal union, in the final analysis deny the vicarious atonement of Christ (satisfactio vicaria), since the redemption of lost and sinful mankind could be effected only by the God-man. Eutychianism and Nestorianism both lead to Unitarianism (Modernism), or to the error that Christ was a mere man.
The same may be said of the error of kenoticism, or the doctrine that the Son of God in His incarnation emptied Himself (ἐκένωσεν, Phil. 2, 7) of His divine attributes of omnipotence, omnipresence, and omniscience (Thomasius, Delitzsch, Kahnis, Luthardt, etc.) or of His divine consciousness and personality (Gess, Hofmann, Frank). Through this “self-limitation” of the Son of God the mystery of the incarnation is indeed explained, but at the tremendous cost of denying Christ’s true deity. For if God has laid aside His divine attributes, He has laid aside His divine essence and has thus become a mutable being, who cannot be true God.
As we reject kenoticism, so we must reject also the error of autohypostasism (αὐτοῦὔπόστατος), according to which the Son of Man constituted a separate person (ἰδιοσύστατος), who either gradually coalesced with the divine person of the X6yog (Dorner) or remained separate altogether (Seeberg, Kirn, etc.). If that were true, Christ would be a mere man, in whom God merely worked in an extraordinary measure. If autohypostasism is adopted, the personal union, or the doctrine of Christ’s two natures, is surrendered, and extreme Modernism, with its absolute denial of Christ’s deity, is the only alternative.
The mystery of the incarnation can never be explained by reason; it must either be believed in toto or rejected in toto. At this point, as before all mysteries of divine revelation, the theologian stands at the crossroads, and he must choose either the way of Christian faith or that of pagan unbelief.