Introduction

The Hypostatic Union in Jesus Christ, the Incarnate Word, designates the union of His human nature with His divine nature in His one divine hypostasis or person. The Hypostatic Union also can designate the union of Christ’s human nature to His one divine hypostasis. This union is the result of the Word becoming flesh (see Jn 1:14). It is the result of Jesus Christ, being in the form of God, emptying himself and taking on the form of man (see Phil 2:6–8). It is the result of the Son of God being conceived and born of Mary (see Lk 1:35). It is the result of the Son being sent to do the saving and sacrificial will of the Father by taking on the body that was prepared for Him (see Heb 10:5–7). The Hypostatic Union is the reason why the man Jesus, with a human voice expressing human thought, could claim divinity with the statement that before Abraham was, I AM (see Jn 8:58). It is the reason for the apostolic witness that what was from the beginning with the Father, Eternal Life, was seen and touched and manifested sensibly to us (see 1 Jn 1:1–3). It is the reason why St. Thomas the Apostle could claim by faithful witness that the one bearing wounds in front of him was his Lord and his God (see Jn 20:28). The Catechism of the Catholic Church states the centrality of the Hypostatic Union for the Catholic faith and for Christian joy: “Belief in the true Incarnation of the Son of God is the distinctive sign of Christian faith: ‘By this you know the Spirit of God: every spirit which confesses that Jesus Christ has come in the flesh is of God’ (1 Jn 4:2). Such is the joyous conviction of the Church from her beginning whenever she sings ‘the mystery of our religion’: ‘He was manifested in the flesh’ (1 Tm 3:16)” (CCC no. 463).

I. The Meaning of the Term "Hypostatic Union"

St. Augustine states the truth of the Hypostatic Union succinctly: “The same one who is God, is man. And the same one who is man, is God. Not through the confusion of the natures, but through the unity of the person” (Augustine, Sermon 186, 1). The Hypostatic Union is a mystery of faith, but we are still able to articulate in a limited and true way what is revealed to us by the coming of the Word in the flesh. Why is “Hypostatic Union” an appropriate term for how humanity and divinity are related incarnationally in Christ? What is a union, and what is a hypostasis?

Union

A union is a kind of coming together of distinct things under a single principle that has unity (see Nicolas, On the Incarnation and Redemption, 47–50). There are many kinds of union based on different kinds of principles of unity and how they unite distinct things into a union. To give examples, the union of the Trinity is a union of persons in the unity of one nature as principle of union. The union of the members of the Church has as one of its principles the unity of charity. The union of the human body is a union of the members of the body that has as its principle the unity of the human soul as the common principle of life.

What Hypostatic Union signifies is that the union of the divine and the human in Christ is based on the principle of the unity of the Second Hypostasis of the Trinity, the only-begotten Son. A particular human nature is in union with the person of the one Son because it is truly His nature by which He is man, and through which He operates with His own actions. The divine and human natures are in union insofar as they are both natures of the one hypostasis who is the Son of God.

One measure to judge the strength or greatness of a union is by the greatness of the principle of unity. A divine person or hypostasis has a supreme, uncreated, super-subsisting unity, which is not composed on the hypostatic level at all. Each person of the Trinity is God in His absolute, incomposite simplicity. In this respect, the Hypostatic Union is the greatest of unions based on the transcendent unity of the divine hypostasis of the Word. As St. Thomas Aquinas writes:

Therefore, the union of Incarnation may be taken in two ways: first, in regard to the things united; secondly, in regard to that in which they are united. And in this regard this union has a pre-eminence over other unions; for the unity of the Divine Person, in which the two natures are united, is the greatest. (Aquinas, <em>ST</em> III, q. 2, a. 9)

Hypostasis

The Greek word hypostasis (ὑπόστασις) comes from hypo, meaning “under,” and statis, meaning “position” or “state.” A hypostasis, on a basic etymological level, is something that stands under or remains. The ancient Greek usage of hypostasis was fairly broad. The English meaning of hypostasis in theological circles today bears the meaning of a subsistent being or a supposit, such as a person.

The Greek-speaking theologians came to see the appropriateness of the term for distinguishing the Father, Son, and Holy Spirit, each as distinct hypostases. Though it has connotations all its own, hypostasis became a functional equivalent to suppositum or persona in the theology of Christ or the Trinity. If one is to navigate early Church teaching correctly, however, one should be aware that it took some time for hypostasis to mean the subsistent real thing exclusively and to lose its broader meaning that might include something like essence. The term gained this precision of meaning in the second half of the fourth century. In 362 AD, St. Athanasius read his Tomus ad Antiochenos to a Synod in Alexandria, allowing what would be the normative use of hypostasis and ousia (essence). This was to become more universal in 382 AD with the Synod of Constantinople. Ocariz explains in more detail:

The term hypostasis underwent considerable evolution prior to obtaining its final theological meaning. Etymologically, hypostasis means that which underlies, the foundation. The New Testament sometimes uses it to designate something that has consistency, something real and objective, as opposed to subjective (cf. 2 Cor 9:4, Heb 1:3; 3:14; 11:1) That is how it is used in the council of Nicaea, when it refers to the Arian position which said that the Son is “of a different hypostasis or ousia” from the Father, using both terms in the sense of substance or nature or essence. (Ocariz, <em>The Mystery of Jesus Christ</em>, 105)

However, this general and early sense of hypostasis as something that is most real gave rise to a more theologically specific sense. Ocariz goes on:

The term <em>hypostasis</em> is also used to designate the divine Persons to show their distinction from one another and when this happens the meaning comes to be the opposite of <em>ousia</em>. For example, though he still uses <em>ousia</em> and <em>hypostasis</em> as sometimes meaning the same, Origen avoids using <em>ousia</em> to describe the three Persons; he uses <em>hypostasis</em> instead. Dionysius of Alexandria already condemns those who say that in the Godhead the three hypostases are separated from each other. Prior to the year 362, the word <em>hypostasis</em> continued to mean objective reality and, when applied to the divine essence, it could mean the same as <em>ousia</em>, but when applied to the divine Persons considered in themselves it acquired a more exact meaning of complete “substance”, that is, an independent subject counterposed to <em>ousia</em>. (Ocariz, <em>The Mystery of Jesus Christ</em>, 105)

It should be noted that, in addition to hypostasis being counterposed with ousia, it is also counterposed with the Greek term physis, or “nature.” To put it simply, the three hypostases of the Trinity are typically distinguished from the one ousia of God, or the essence or being of God, and the one hypostasis of Christ is typically distinguished from His two physes or natures. Understanding this distinction is vital to understanding the theology of the Hypostatic Union, as will be further explained below.

Hypostasis as Distinct from Nature or Essence

Whereas “nature” connotes what something is that manifests itself according to its principles of motion and operation, “hypostasis” connotes a certain entirety of being on the level of subsistence. A nature or essence is not something that subsists in itself but is rather a principle of being that makes a hypostasis be a certain kind of thing. If one were to ask who Christ is, a proper response would be a hypostasis, a personal divine being; but if one were to ask what Christ is on the basic level, the answer would be divine and human, referring to His natures. It is therefore not a contradiction to understand two natures of Christ that come together in the union of one hypostasis. Christ, a single subject, has two distinct essential principles. The One Thing, as it were, that Christ is, after the Incarnation, has two distinct natures, and indeed is divine and human. The person of Christ considered in itself is simple and uncomposed. However, insofar as the person of Christ exists by two natures, He is composed by being both human and divine without confusion (see Aquinas, ST III, q. 2, a. 4). Many errors arise if one does not see that a distinct second nature does not necessitate an additional distinct hypostasis or person.

St. John Damascene summarizes the theology of how the one hypostasis of Christ relates to His human nature:

An hypostasis <em>is</em> in the proper sense of the term. Hypostasis is that which subsists, or is independently. A nature which is assumed by an hypostasis and exists dependently on it is said to be hypostasized by this hypostasis. Thus the human nature of Christ never subsisted for one moment of itself, and was never a natural hypostasis; it was hypostasized by the Word. It subsists, therefore, through the hypostasis of the Word which this human nature had and still has for its hypostasis. Hypostasis is taken here to mean the same as person. (St. John Damascene, <em>Dialectica</em>, 43 and 44 as quoted in Ferrier, <em>What is the Incarnation?</em>, 89–90)

As St. John Damascene says, a hypostasis is in the proper sense, that is, it exists independently from other created being. The human nature is hypostasized through the person, which means that the human nature depends on the person and does not exist as a nature except in union with the person. Just as the human nature of a human person is a real nature only by connection to that human person, likewise the human nature of Christ is a nature only by its Hypostatic Union to the person of the Word. There was no preexisting individual human nature that the Word took up. Rather, the individual human nature came to be in the very act of the Word assuming it as Mary conceived Him. This occurred by the one power of God, often appropriated to the Holy Spirit. There was not a preexistent human taken over by the person of the Word. There was the human, Christ, whose human nature resulted when the Word became man. That is why the Catechism affirms: “Everything that Christ is and does in this [human] nature derives from ‘one of the Trinity’. The Son of God therefore communicates to his humanity his own personal mode of existence in the Trinity. In his soul as in his body, Christ thus expresses humanly the divine ways of the Trinity” (CCC no. 470). There is one act of being in Christ in the supposital and hypostatic sense (see Dauphinais, Thomas Aquinas and the Crisis of Christology, 70–98). That act of being does not depend on His human nature, but His human nature does depend on His one divine act of being. The hypostasis of the Word only depends on the human nature of Christ to be human, not to be simply speaking.

II. Church Teaching on the Hypostatic Union

Official Catholic Church teaching about the Hypostatic Union, historically speaking, was most often done in response to some heresy. In articulating responses to heresy, theological precision was gained. However, it would not do justice to the mystery of the Hypostatic Union to see it simply as a negation of heresy rather than the wondrous reality that it is. Nor should an awareness of heresies make one primarily think, in fear, of the Hypostatic Union as a minefield of possible errors. Nevertheless, plotting out the various heresies can lead to a clearer positive notion of the mystery.

The Historical Development of the Church’s Articulation of the Hypostatic Union

Heresies regarding the Hypostatic Union can center around a denial of Christ’s true humanity, a denial of Christ’s true divinity, or a denial of the true unity in Christ that is the source of the union of the two natures. Even if these three things are nominally held, someone could in effect deny one of them by denying some necessary consequence of them. In some ways the history of the prominent Christological errors can be seen as a kind of pendulum swing, each heresy in turn denying Christ’s humanity, divinity, or proper union.

The Catechism gives a good summary of Christological errors. “The first heresies denied not so much Christ’s divinity as his true humanity (Gnostic Docetism). From apostolic times the Christian faith has insisted on the true incarnation of God’s Son ’come in the flesh’” (CCC no. 465). The early Church’s vigorous denial of Gnostic Docetism is important because it set the stage for the Church’s continual affirmation of the basic goodness of matter and of the natural order. That an actual human nature was assumed by the Son should put to rest dualistic tendencies condemning the material order as such or seeing it as contrary to the holy. Affirmation of the Incarnation of Christ and the goodness of the created order always go hand in hand.

Heresies concerning the divinity of Christ inevitably came. “But already in the third century, the Church in a council at Antioch had to affirm against Paul of Samosata that Jesus Christ is Son of God by nature and not by adoption” (CCC no. 465). This heresy of Adoptionism was in some ways a precursor to Nestorianism (explained below). Adoptionism asserts full human personhood in Christ who was in some way divinized. While it is true that the human nature of Christ has elements that are the exemplars of our divinization and divine adoption, such as sanctifying grace and the indwelling of the Holy Spirit, nevertheless Christ is the Son of God by nature, not by adoption. He is a divine person who took a human nature, not a human person who was elevated.

A denial of the full divinity of Christ also came in the form of Arianism. “The first ecumenical council of Nicaea in 325 confessed in its Creed that the Son of God is ’begotten, not made, of the same substance (homoousios) as the Father,’ and condemned Arius, who had affirmed that the Son of God ’came to be from things that were not’ and that he was ’from another substance’ than that of the Father’” (CCC no. 465). The full and equal divinity of Christ came to be affirmed by creed and became a touchpoint of Christological orthodoxy.

Apollinarianism not only denied the integral humanity of Christ but misunderstood the mode of union in Christ as well. “Apollinarius of Laodicaea asserted that in Christ the divine Word had replaced the soul or spirit. Against this error the Church confessed that the eternal Son also assumed a rational, human soul” (CCC no. 471). The denial of the human soul of Christ was a precursor to the Monophysite heresy (explained below). It is important that the humanity and divinity are not parts that fit together to form a natural union. The divine person of Christ is a whole who takes to Himself a whole human nature upon which His personhood does not depend. The whole human nature, in turn, means that Christ had a human soul by which He knew on earth according to the complete capabilities of human knowledge, willed and loved in a perfectly human way, and had an integral human body with senses and emotions.

The Nestorian and Monophysite heresies, and the responses to them by the Councils of Ephesus and Chalcedon respectively, are critical moments in the history of Catholicism. Those councils taken together offer a clear and relatively exhaustive understanding of Christ as divine and human. Those councils are a frame of reference for what comes before and after and are perennially enlightening. The Catechism explains Nestorianism and quotes a representative section from Ephesus:

The Nestorian heresy regarded Christ as a human person joined to the divine person of God’s Son. Opposing this heresy, St. Cyril of Alexandria and the third ecumenical council, at Ephesus in 431, confessed “that the Word, uniting to himself in his person the flesh animated by a rational soul, became man.” (Council of Ephesus (431): DS 250) Christ’s humanity has no other subject than the divine person of the Son of God, who assumed it and made it his own, from his conception. For this reason the Council of Ephesus proclaimed in 431 that Mary truly became the Mother of God by the human conception of the Son of God in her womb: “Mother of God, not that the nature of the Word or his divinity received the beginning of its existence from the holy Virgin, but that, since the holy body, animated by a rational soul, which the Word of God united to himself according to the hypostasis, was born from her, the Word is said to be born according to the flesh.” (Council of Ephesus: DS 251; <em>CCC</em> no. 466)

The Catholic faithful do not address or pray to a human Christ and to a different divine Christ in turns. There is one Christ, divine and human, who is the object of faith and love.

While the chief concern of Ephesus was to affirm the unity of Christ, it nevertheless states clearly that the Word united to Himself “flesh animated by a rational soul” and “became man,” and similar things. Notwithstanding, there were some large factions who did not maintain that humanity and divinity were both completely in Christ as distinct. Just twenty years after Ephesus, the Council of Chalcedon was called to address the full and true humanity of Christ while recapitulating previous teaching. Again, the Catechism explains this heresy along with a representative quote from the Council of Chalcedon:

The Monophysites affirmed that the human nature had ceased to exist as such in Christ when the divine person of God’s Son assumed it. Faced with this heresy, the fourth ecumenical council, at Chalcedon in 451, confessed:

“Following the holy Fathers, we unanimously teach and confess one and the same Son, our Lord Jesus Christ: the same perfect in divinity and perfect in humanity, the same truly God and truly man, composed of rational soul and body; consubstantial with the Father as to his divinity and consubstantial with us as to his humanity; “like us in all things but sin.” He was begotten from the Father before all ages as to his divinity and in these last days, for us and for our salvation, was born as to his humanity of the virgin Mary, the Mother of God.” (Council of Chalcedon (451): DS 301; cf. Heb 4:15)

“We confess that one and the same Christ, Lord, and only-begotten Son, is to be acknowledged in two natures without confusion, change, division or separation. The distinction between the natures was never abolished by their union, but rather the character proper to each of the two natures was preserved as they came together in one person (prosopon) and one hypostasis.” (Council of Chalcedon: DS 302; <em>CCC</em> 467)

The Church further clarified at the fifth ecumenical council, at Constantinople in 553, that “there is but one hypostasis,… which is our Lord Jesus Christ, one of the Trinity” (Council of Constantinople II (553): DS 424; CCC no. 468). If one refuses to affirm any additional human person in Christ but still affirms that the humanity of Christ is somehow a separate subject or has some kind of hypostatic being in itself, that would still not be the one Christ.

The patristic and conciliar Christology ranks among the chief blessings of theological patrimony in the Catholic Church.

The Theological Landscape of the Early Greek Church

To further contextualize the early Church teaching on the Hypostatic Union, it would be helpful to go over the theological landscape of the Greek-speaking Church where foundational Christology primarily developed. That will put the various heresies above, and the Church’s response to them, into a conceptual framework. Of the two principles of the Hypostatic Union—the unity of Christ’s person or hypostasis on the one hand, and the respective integrity of the two natures on the other—neither ought to be affirmed in such a way as to negate the other.

Theologians and historians of patristic thought often distinguish between two broadly classifiable theological perspectives: the Alexandrian School and the Antiochene School, named after the cities of Alexandria and Antioch that had actual schools where each of these perspectives was exemplified (see Grillmeier, Christ in Christian Tradition, 183–302). It is to be noted from the outset that any two theological approaches that are orthodox will be closer to one another than either would be to an unorthodox approach that might come from the same milieu. So, there is something misleading in grouping orthodox and heterodox positions together and distinguishing them from another set of positions that is both orthodox and heterodox. It also is to be noted that many of the Fathers of the Church do not fall neatly into either broad school of thought, but have aspects from both, such as the Cappadocian Fathers.

That being said, the Christology of the Alexandrian School is noted for its frequently used Logos-sarx model of union in Christ, and the Antiochene school is noted for its frequent use of the Logos-anthropos model of union in Christ. The Logos-sarx model, Logos meaning “Word,” the Eternal Son of God, and sarx meaning “flesh,” tends to emphasize the unity of Christ, with a concomitant emphasis on Christ’s divinity as a starting point for Christological thought. Even granting that sarx or “flesh” is used as synecdoche (the whole being named for the part), the humanity of Christ was seen more as something assumed by the Word. The Logos-anthropos model, anthropos meaning a human or a man inclusively, is more comfortable with a human and divine distinction, and tends to emphasize the humanity of Christ as a starting point. One can see nascent starting points for the Alexandrian and Antiochene Schools in the Gospel of John and the Synoptic Gospels respectively. St. Cyril of Alexandria is an example of a Father and Doctor in the Alexandrina School, and St. John Chrysostom that of the Antiochene School.

The orthodox versions of these two schools are entirely compatible, complementary, and each corrective of warping excesses. The Word was made flesh and assumed a human nature to the unity of His single personhood. It is equally true that the humanity and divinity of Christ are distinct natures, each with their own proper operation. The doctrine of the Hypostatic Union of unmixed natures is the common feature of orthodox versions of both these schools, regardless of differences in emphasis and in the development of theological vocabulary.

If someone thinking along the lines of a Logos-sarx model were to deny that there was a human soul in Christ, and that human flesh was assumed in such a way that the divinity of Christ functioned in place of soul in a kind of natural compositional unity, one would veer into the heresy of Apollinarianism. Even if one were to affirm the soul of Christ and still look at the assumption of humanity as a kind of natural absorption into unity, one would veer off into the heresy of Monophysitism.

If someone thinking along the lines of a Logos-anthropos model were to affirm that Christ being anthropos, or a human, necessitates human personhood in Christ, as opposed to seeing Christ as human in terms of the assumption of a human nature to a divine person, then one would veer off into the heresy of Nestorianism. An extreme hypostatic duality in Christ would be Adoptionism.

The history of the development of Christology in the Church can be seen as discernment, led by the Holy Spirit, about what core of belief is common regardless of whether one thinks of Christ starting with what is humanly experienced pointing to a belief in His divinity, or if one first thinks of Christ as divine and reasons to what that would mean about His humanity. The Hypostatic Union is a mystery of faith that can be examined from many angles.

Hypostatic Union: Not a Natural Mode of Union

That the union in Christ is a Hypostatic Union means that the union is not a union in a nature itself, though two natures are united. Incorrect views arise when one thinks of the union in Christ as a natural union that is not based on the unity of the person of Christ. St. Thomas Aquinas distinguishes three possible types of natural union, each of which, were it the union in Christ, would lead to some sort of heresy (see Aquinas, ST III, q. 2, a. 1).

Accidental Union

The first type of natural union, which looks no farther than nature as a principle of union, would be if two natures in complete integrity existed in some kind of juxtaposition. This would be an accidental union, based on the philosophical accidents of the natures of the things in union. General examples of this kind of union are the union of two things in physical proximity or the union of persons insofar as they know or love each other. An example of a heretical understanding of the union of Christ utilizing this notion of accidental natural union is Adoptionism, or a weak Nestorianism, where the human nature of Christ exists in a human person as separate from the divine person, except for an indwelling or a coordination of wills. Since personhood is not the principle of union in these heresies, maintaining one person in Christ is not a priority.

Mixed Union

The second way of being in a strictly natural union that is not hypostatic is if the natures start out as complete, whole natures and then are mixed such that each nature is changed into some third nature. A general example of this kind of union would be chemical elements forming a compound. An example of a heretical understanding of this type of combination or mixed natural union in Christ would be Eutychianism or Monophysitism, where only one nature results from the union of what started out as two natures. Here again, personhood is not seen as a principle of union. In wanting to maintain Christ’s unity, these heresies hold that the two natures need to be combined into one nature.

Union of Integral Parts

The third way natures can be in a natural union that is not hypostatic is when the two so-called natures are in fact principles or aspects or “parts” of a nature that, when they come together, make a whole nature. An example would be a body and a soul. When a body and a soul are united, a single complete human nature results. An example of a heretical understanding of this type of union would be Apollinarianism, where merely a material body, or a material body with an animal soul, is united to the Son of God. The divine life and power, in this hypothetical case, would supply for what a properly human soul would provide. Here again unity in Christ is a priority, but it is at the cost of the integral completeness of Christ’s humanity. The unity of personhood is not considered as the “place” of Christ’s unity as it ought to be.

The person of Christ is whole and entire irrespective of the human nature that is joined to it. “The unique and altogether singular event of the Incarnation of the Son of God does not mean that Jesus Christ is part God and part man, nor does it imply that he is the result of a confused mixture of the divine and the human. He became truly man while remaining truly God. Jesus Christ is true God and true man” (CCC no. 464). The human nature of Christ, in fact, would not be at all if it were not assumed by the divine person. In this respect, the human nature of Christ is truly His and belongs to Him every bit as much as a human nature belongs to a created human person. The difference is that the human nature of a created human person is necessary for that person to be a person at all, whereas the human nature of Christ, while necessary for Him to be human, is not necessary for Him to be a person.

The overall conclusion is that the mode of union in Christ is not a natural union. In other words, it is not by having two natures become one nature, or two natures simply existing side by side that Christ is one. He is one by the unity of hypostasis or person, the person possessing two natures in their distinction, and bringing them together as both His.

III. Theological Consequences of the Hypostatic Union

An account of all of the theological consequences of the Hypostatic Union would encompass most of the Catholic faith. The consequences discussed in this section will be the more immediate consequences of the union that ultimately will aid in the understanding of what the union entails.

Divine Immutability and Real Union

The Hypostatic Union is a real union in the divine person of Christ. It is a union that came to be when Christ was conceived in the womb of the blessed Virgin Mary. When the Son of God became incarnate, the Word was made flesh by a union of the divine and human natures in the one Hypostasis of the Word. That does not mean, however, that the Word underwent a change in His divine nature or an alteration of His divine personhood. The Hypostatic Union does not bring about any intrinsic change to the divine hypostasis (see Ocariz, The Mystery of Jesus Christ, 78–81).

God did not change when He created the universe, nor does He change when anything in the created order changes. The exercise of God’s power means that something in the created order changes, not the divine power itself or God Himself. Similarly, God did not change when the Word assumed a human nature. God, by the one, divine, immutable power, created a human nature as the nature of the Son. The human nature of Christ is concretely constituted such that it relates back to the Son, and the Son alone, as its subject and hypostasis, without that entailing a change in the Son’s divinity. Nonetheless, the Son is the one who became human even if He did not undergo a change intrinsic to His divinity in so doing. This is similar to how God became a creator of a particular thing when He created it, and that thing relates back to God with the relation of being created by Him, without God undergoing any intrinsic change in His divinity.

This lack of change in the Word’s divine nature when He took on a human nature is affirmed by the fact that the divine nature in the union did not undergo any kind of mixture or enter into natural composition with the humanity of Christ. While human nature can undergo changes and remain stable in being a human nature, the divine nature does not have accidents and undergoes no accidental change in its stability. This is so even as a human nature enters into union with it. Christ did and can change after the Incarnation, and this can be affirmed without equivocation. But that Christ can change is only true based on the human nature that He assumed.

St. Paul speaks in eye-opening terms of the self-emptying or kenosis of Christ in His incarnation and death. (Phil 2:7) What does this mean in terms of divine immutability? As Pope St. John Paul II says, “‘He emptied himself’ does not in any way mean that he ceased to be God; that would be absurd!” (Jesus, Son and Savior, 311) This is St. Thomas Aquinas’s memorable commentary:

He says, therefore, He <em>emptied himself</em>. But since He was filled with the divinity, did He empty Himself of that? No, because He remained what He was; and what He was not, He assumed…

How beautiful to say that He <em>emptied himself</em>, for the empty is opposed to the full! For the divine nature is sufficiently full, because every perfection of goodness is there. But human nature and the soul are not full, but capable of fullness, because it was made as a slate not written upon. Therefore, human nature is empty. Hence he says, He <em>emptied himself</em>, because He assumed a human nature. (Aquinas, <em>Commentary on Philippians</em>, ch. 2, lect.2, emphasis original)

The Grace of Union

In Christ, because of the Hypostatic Union, there is what is known as the grace of union. The human nature of Christ is a true integral nature, the same nature as ours. However, the relation of union in the person, insofar as it is grounded in the human nature of Christ, is a singular supernatural grace. It does not proportionally pertain to human nature (or any possible created thing in a natural order) to have a divine person as its subject. Christ is graced, in an absolutely unique way, in that His human nature is actual due to a personal union with the Word. The supernatural grace of union, proper to Christ, has ramifications in other types of grace.

A fullness of sanctifying grace, distinct from the grace of union, results from the joining of the human and divine natures in one person. As St. Thomas Aquinas explains it: “For grace is caused in man by the presence of the Godhead, as light in the air by the presence of the sun…But the presence of God in Christ is by the union of human nature with the divine person. Hence the habitual [sanctifying] grace of Christ is understood to follow this union, as light follows the sun” (Aquinas, ST III, q. 7, a. 13). Christ is “full of grace and truth” (Jn 1:14) so He possesses grace to the fullest, in the sense that there is no perfection possible with respect to sanctifying grace that Christ does not have. “Now on the part of grace itself there is said to be the fulness of grace when the limit of grace is attained, as to essence and power, inasmuch as grace is possessed in its highest possible excellence and in its greatest possible extension to all its effects. And this fulness of grace is proper to Christ” (Aquinas ST III, q. 7, a. 10). Other people can have a fullness of grace in another sense, meaning that they have the full amount for their God-given state or mission in life, the Blessed Virgin Mary being the prime example of a relative fullness of grace.

The Hypostatic Union is also the reason why Christ possessed the fullness of all the charismatic, or gratuitous, graces. Charismatic graces are ordered to manifest or confirm in the way of faith and spiritual doctrine. Since Christ was the Teacher par excellence, He, as evidenced in Scripture, was able to confirm His doctrine. It was the union of His human soul with the Person of the Word that gave Him the ability to do things proportioned to divine power through His humanity: “As sanctifying grace is ordained to meritorious acts both interior and exterior, so likewise gratuitous grace is ordained to certain exterior acts manifestive of the faith, as the working of miracles, and the like. Now of both these graces Christ had the fulness, since inasmuch as His soul was united to the Godhead, He had the perfect power of effecting all these acts (Aquinas ST III, q. 7, a. 7, ad. 3). Hence we see the grace of union, a direct corollary of the Hypostatic Union, as a kind of origin of all grace of the New Law, as exemplified in Christ, and participated in by the Church.

Theandric Action

There is one person in Christ who is the subject of all of the actions and operations of Christ. However, there are two natures of Christ united in the one person, by which natures His actions are done. The Fathers of the Church therefore speak of two “operations” in Christ, divine and human, and therefore of two intellects and two wills.

It is true to say that the upholding of the universe in existence is done by Christ because He is a divine person possessing the one divine nature and the one divine power to uphold the universe. His human nature is not the proper principle of that act. It is also true to say that a given act of carpentry was done by Christ when He walked the earth by an act that is proportioned to human nature. It is still the one divine person who upholds the universe and saws the wood, though now through one nature, and now through another. Those acts proportioned to His human nature are still ennobled by the fact that they are done by a divine person and can be called “theandric” (divine-human) in an extended sense. This ennoblement means that the human actions of Christ directed toward God, such as His merit and prayer, are not limited in their potential efficacy (see Journet, The Church of the Word Incarnate, Vol. 2, 203–10).

There are also other cases recorded in Scripture, such as His miracles, and especially His saving and redemptive acts, that do not fit neatly into either divine act exclusively or human act exclusively. These are acts that only God could do but are still done through the concurrent instrumental action of Christ’s humanity. An instrument is something a principal cause employs to produce an effect. The instrument’s proper activity is involved; however, the effect is not proportioned to the nature of the instrument itself, but rather to the principal cause. Christ’s humanity is a conjoined, not a separate, instrument of His divine person. Nevertheless, His humanity is an instrument, and actions done by means of Christ’s human nature that have the divine nature as their principal cause are called theandric in the strict sense.

It still is true with these theandric acts that Christ’s two natures remain distinct, but there is a unity of effect as in other instances of a single effect when an instrument is in use. Hence, there is a lack of distinction in operation on the side of the effect when Christ’s human nature acts as a conjoined instrument of divine power. This leads St. Thomas to write the following:

…the action of the instrument as instrument is not distinct from the action of the principal agent; yet it may have another operation, inasmuch as it is a thing. Hence the operation of Christ’s human nature, as the instrument of the Godhead, is not distinct from the operation of the Godhead; for the salvation wherewith the manhood of Christ saves us and that wherewith His Godhead saves us are not distinct; nevertheless, the human nature in Christ, inasmuch as it is a certain nature, has a proper operation distinct from the Divine… (Aquinas, <em>ST</em> III, q. 19, a. 1, ad 2)

Insofar as we see the human acts of Christ in their pure instrumentality, that is, we see them in conjunction with those effects that only God can do, they have a divine effect. In the case of Christ’s saving death, Christ’s humanity is a conjoined instrument due to the Hypostatic Union, so His death really saves us with divine power. Likewise, His Resurrection and Ascension have real agency in granting us eternal, resurrected life. As the Third Council of Constantinople puts it, “The difference in natures in that same and unique hypostasis is recognized by the fact that each of the two natures wills and performs what is proper to it in communion with the other. Thus, we glory in proclaiming two natural wills and actions concurring together for the salvation of the human race” (Denzinger, 558).

The Communication of Idioms

The Hypostatic Union is the reason why we can use what is known as the communication of idioms with Christ. The communication of idioms gives an account for why a divine characteristic can be predicated of a human name of Christ, or why a human characteristic can be predicated of a divine name for Christ. Some examples would be “the Son of Mary created the universe” or “God died on the cross.”

Christ being one divine hypostasis with a human nature and a divine nature means that He can rightfully be called a man, because a man is a person with a human nature. But when He is called man, or human, or something connoting humanity in the subject of predication, it is not just the human nature that is indicated, but the whole hypostasis, albeit by a name that connotes humanity. Since it is the whole hypostasis that is being indicated by the human term as grammatical subject, then anything true of the hypostasis is truly said of that term, including divine attributes and operations. Pointing to Christ, one can truly say “this man is God.” Likewise, when Christ is called “God,” “Lord,” “The Almighty One,” or anything that connotes His divinity as a subject of predication, that subject includes His human nature. Hence, we can say God walked the earth and shed tears. As the Catechism says, “Thus everything in Christ’s human nature is to be attributed to his divine person as its proper subject, not only his miracles but also his sufferings and even his death: ‘He who was crucified in the flesh, our Lord Jesus Christ, is true God, Lord of glory, and one of the Holy Trinity’” (Council of Constantinople II (553): DS 432; cf. DS 424; Council of Ephesus, DS 255; CCC no. 468).

The communication of idioms does not mean that what is true about the human nature of Christ is also true of His divine nature. It is not a confusion of natures or an exchange of properties from one nature to another that is happening. Rather, the idioms or properties of human nature and divine nature are both properties of the person of Christ. Just as the hypostasis is the “place” of union of natures in Christ, so is the hypostasis the “place” where divine and human idioms or properties have a common subject.

Whether one admits the communication of idioms is a kind of test case for whether one truly believes in the Hypostatic Union. For instance, Nestorius’s denial that Mary was the mother of God indicated a lack in belief of the full sense of Hypostatic Union.

The “rules” for the communication of idioms can get rather complicated, especially when reduplication is involved (i.e., when one qualifies statements about Christ with “as man” or “as God.”) (see Aquinas ST III q. 16). The point here is not to be exhaustive in examples or to explain difficult test cases. Rather, it is to give the theoretical theological justification for predicating formally of Christ either divine or human things, notwithstanding whether a divine or human name denominates Him materially as a subject of the predication.

IV. The Hypostatic Union and Redemption

The Nicaean Creed tells us that the Son came down from Heaven and became man “for us men and for our salvation.” Without going into the theology of Redemption in its entirety, there are some notable ways in which our redemption and the saving acts of Christ are intimately tied up with the Hypostatic Union.

Mediation and the Hypostatic Union

The Son of God hypostatically united to Himself a human nature, which has great repercussions with respect to our redemption from sin. As Nicolas writes, the Incarnation is already redemptive and is the first of the saving acts by which our redemption is accomplished:

Therefore, the Incarnate Word was sent for man’s redemption. He accomplished this mission by giving His life as a sacrifice and by receiving it anew through the resurrection. But by the Incarnation itself, man’s salvation has already begun. In the Man-Jesus, the image of God, which was eroded by sin, is already restored, for this man is the Word, the eternal and perfect image of the Father. He restored it by realizing, in Himself first of all and perfectly, the divine intention to make man in His image. He restored it inchoately and virtually in all of humanity because mankind was in some way contained in Him. In the Incarnation, the recapitulation of all things in Christ already begins. The Incarnation is already redemptive. (Nicolas, <em>On the Incarnation and Redemption</em>, 285–6)

The decree from the Second Vatican Council on the missionary efforts of the Church, Ad gentes, speaks eloquently of the salvific intent behind the Hypostatic Union:

Now God, in order to establish peace or the communion of sinful human beings with Himself, as well as to fashion them into a fraternal community, did ordain to intervene in human history in a way both new and finally sending His Son, clothed in our flesh, in order that through Him He might snatch men from the power of darkness and Satan (cf. Col. 1:13; Acts 10:38) and reconcile the world to Himself in Him (cf. 2 Cor. 5:19). Him, then, by whom He made the world, (cf. Hebrews 1:2; John 1:3 and 10; 1 Cor. 8:6; Col. 1:16.) He appointed heir of all things, that in Him He might restore all (cf. Eph. 1:10). (<em>AG</em> no. 3)

The decree then goes on to speak of the mediatorial role that Christ has due to the union of a human nature to His person:

For Jesus Christ was sent into the world as a real mediator between God and men. Since He is God, all divine fullness dwells bodily in Him (Col. 2:9). According to His human nature, on the other hand, He is the new Adam, made head of a renewed humanity, and full of grace and of truth (John 1:14). Therefore the Son of God walked the ways of a true Incarnation that He might make men sharers in the nature of God: made poor for our sakes, though He had been rich, in order that His poverty might enrich us (2 Cor. 8:9). The Son of Man came not that He might be served, but that He might be a servant, and give His life as a ransom for the many—that is, for all (cf. Mark 10:45). The Fathers of the Church proclaim without hesitation that what has not been taken up by Christ is not made whole. (Cf. St. Athanasius, <em>“Letter to Epictetus,”</em> 7 (PG 26, 1060); St. Cyril of Jerusalem, <em>“Catech.”</em> 4, 9 (PG 33, 465); <em>AG</em> no. 3)

Pope St. John Paul II ties the redemptive mission of Christ inextricably up with the Hypostatic Union. He does so from the perspective of God’s intentional and effective providence and the history of salvation:

“In many and various ways God spoke of old to our fathers by the prophets; but in these last days he has spoken to us by a Son...” (Heb 1:1–2), by the Son, his Word, who became man and was born of the Virgin Mary. This act of redemption marked the high point of the history of man within God’s loving plan. God entered the history of humanity and, as a man, became an actor in that history, one of the thousands of millions of human beings but at the same time unique! Through the Incarnation God gave human life the dimension that he intended man to have from his first beginning; he has granted that dimension definitively—in the way that is peculiar to him alone, in keeping with his eternal love and mercy, with the full freedom of God—and he has granted it also with the bounty that enables us, in considering the original sin and the whole history of the sins of humanity, and in considering the errors of the human intellect, will and heart, to repeat with amazement the words of the Sacred Liturgy: “O happy fault... which gained us so great a Redeemer!” (John Paul II, <em>Redemptor hominis</em>, no. 1)

Just as there is one Christ in whom humanity is hypostatically united to divinity, so “there is one mediator between God and man, the man Christ Jesus” (1 Tm 2:5). As such, Christ the man is “high priest of the good things that have come” (Heb 9:11).

Unicity of Christ’s Saving Role (Dominus Iesus)

A document from the then Congregation for the Doctrine of the Faith explains the unicity of Christ as Savior in terms of His hypostatic unity:

The doctrine of faith must be <em>firmly believed</em> which proclaims that Jesus of Nazareth, son of Mary, and he alone, is the Son and the Word of the Father. The Word, which “was in the beginning with God”‌ (Jn 1:2) is the same as he who “became flesh”‌ (Jn 1:14). In Jesus, “the Christ, the Son of the living God”‌ (Mt 16:16), “the whole fullness of divinity dwells in bodily form”‌ (Col 2:9). He is the “only begotten Son of the Father, who is in the bosom of the Father”‌ (Jn 1:18), his “beloved Son, in whom we have redemption... In him the fullness of God was pleased to dwell, and through him, God was pleased to reconcile all things to himself, on earth and in the heavens, making peace by the blood of his Cross.”‌ (Col 1:13–14; 19–20; <em>Dominus Iesus</em>, no. 10, emphasis original)

After summarizing the teaching of the Councils of Nicaea and Chalcedon, the document goes on:

For this reason, the Second Vatican Council states that Christ “the new Adam...’image of the invisible God’ (Col 1:15) is himself the perfect man who has restored that likeness to God in the children of Adam which had been disfigured since the first sin... As an innocent lamb he merited life for us by his blood which he freely shed. In him God reconciled us to himself and to one another, freeing us from the bondage of the devil and of sin, so that each one of us could say with the apostle: the Son of God ‘loved me and gave himself up for me’ (Gal 2:20).” (<em>Dominus Iesus</em>, no. 10)

Since it is Christ the man who recapitulates humanity as high priest, one cannot separate the humanity of Christ from His divinity:

In this regard, John Paul II has declared: “To introduce any sort of separation between the Word and Jesus Christ is contrary to the Christian faith... Jesus is the Incarnate Word—a single and indivisible person... In the process of discovering and appreciating the manifold gifts—especially the spiritual treasures—that God has bestowed on every people, we cannot separate those gifts from Jesus Christ, who is at the centre of God’s plan of salvation.” 

It is likewise contrary to the Catholic faith to introduce a separation between the salvific action of the Word as such and that of the Word made man. With the incarnation, all the salvific actions of the Word of God are always done in unity with the human nature that he has assumed for the salvation of all people. The one subject which operates in the two natures, human and divine, is the single person of the Word. (<em>Dominus Iesus, no. 10; <em>Redemptoris missio</em>, no. 6; Leo the Great, <em>Tomus ad Flavianum</em>: DS 294)

The Unity of Christ extends to the unity of the salvific economy:

Similarly, the doctrine of faith regarding the unicity of the salvific economy willed by the One and Triune God must be <em>firmly believed</em>, at the source and centre of which is the mystery of the incarnation of the Word, mediator of divine grace on the level of creation and redemption (cf. Col 1:15–20), he who recapitulates all things (cf. Eph 1:10), he “whom God has made our wisdom, our righteousness, and sanctification and redemption”‌ (1 Cor 1:30). In fact, the mystery of Christ has its own intrinsic unity, which extends from the eternal choice in God to the parousia: “he [the Father] chose us in Christ before the foundation of the world to be holy and blameless before him in love.”‌ (Eph 1:4; <em>Dominus Iesus</em>, no. 11, emphasis original)

The Second Vatican Council’s Dogmatic Constitution on the Church, Lumen gentium, gives a terse statement as to how an incarnational understanding of redemption is part and parcel of an understanding of redemption as centered on the paschal events of Christ’s death and resurrection:

In the human nature united to Himself the Son of God, by overcoming death through His own death and resurrection, redeemed man and re-molded him into a new creation. By communicating His Spirit, Christ made His brothers, called together from all nations, mystically the components of His own Body. (<em>LG</em> no. 7)

There is a recapitulatory nature of the Hypostatic Union; that is, by the Son of God becoming man, humankind had a new head in Christ to replace Adam and the reign of sin. Such a recapitulation, though, cannot be fully understood without reference to the saving events accomplished through Christ’s human nature, in particular, the passion, death, resurrection, and ascension.

The Humanity of Christ as Sacred in Life and Death

By virtue of the Hypostatic Union, we rightfully worship the humanity of Christ, not in isolation from the person of Christ, but as united to Him and included with Him as object of our love and duty (see Aquinas, ST III q. 25, a. 1). The doctrine of Hypostatic Union provides a theological basis for devotions to Sacred Heart, the Precious Blood, and other aspects of the humanity of Christ without violating the principle that God alone is owed the worship of latria.

The Hypostatic Union did not cease even in the death of Christ, as is constantly attested to through the patristic age and after. The death of Christ was the separation of His soul from His body, so it was as real a death as any. The divine person, though, never left the soul or the body of Christ in their separated states. Despite being a subsisting principle, the divine person was not an animating principle of the body of Christ, in life or in death. Only His soul animated His body, so it was truly inanimate in death, though still united to the Word. The lack of dissolution of the Hypostatic Union even in death shows the radicality of the dependence of Christ’s humanity on the divine person as its principle of being. There is no body or soul of Christ under any condition that is not the body and soul of the Word. As the Catechism of the Catholic Church states:

Since the “Author of life” who was killed is the same “living one [who has] risen”, the divine person of the Son of God necessarily continued to possess his human soul and body, separated from each other by death:
“By the fact that at Christ’s death his soul was separated from his flesh, his one person is not itself divided into two persons; for the human body and soul of Christ have existed in the same way from the beginning of his earthly existence, in the divine person of the Word; and in death, although separated from each other, both remained with one and the same person of the Word.” (St. John Damascene, <em>De fide orth.</em> 3, 27: PG 94, 1097; <em>CCC</em> no. 626; Acts 3:15; Lk 24:5–6)

The Catechism goes on to explain that the Hypostatic Union continuing for body and soul in death means the lack of corruption of the body of Christ. That is why the Church has always seen Psalm 16, when it speaks of not letting God’s holy one see corruption, as a reference to Christ: “Christ’s death was a real death in that it put an end to his earthly human existence. But because of the union his body retained with the person of the Son, his was not a mortal corpse like others, for “divine power preserved Christ’s body from corruption” (Aquinas, ST III, q. 51, a. 3; CCC no. 627).

This means that the body of Christ, even when in the tomb, could have been included in the worship of the Word. This means also that there is a saving instrumental efficacy even in the body of Christ in death. As St. Thomas Aquinas writes:

…the Godhead was not separated from Christ’s flesh by death; and therefore, whatever befell Christ’s flesh, even when the soul was departed, was conducive to salvation in virtue of the Godhead united. But the effect of any cause is properly estimated according to its resemblance to the cause. Consequently, since death is a kind of privation of one’s own life, the effect of Christ’s death is considered in relation to the removal of the obstacles to our salvation: and these are the death of the soul and of the body. (Aquinas, <em>ST</em> III, q. 50, a. 6)

The Hypostatic Union stands as the source of the removal of the sting of death in Christ’s death, removing all obstacles to the resurrection of the just.

V. The Hypostatic Union and the Sacramental Economy

Since the Son of God became man “for us men and for our salvation,” the salvific implications of the Hypostatic Union are inexhaustible. One prominent place in which they appear is the sacramental economy. As Pope St. John Paul II states: “[Trinitarian] life is in Christ and is communicated from Christ to humanity through the action of the Holy Spirit for the fulfillment of God’s salvific plan. Instituted by Christ, the sacraments are visible signs of this capacity to transmit new life…” (John Paul II, Jesus, Son and Savior, 370)

The Priesthood of Christ

The sacramental economy is based on Christ’s priesthood, by means of which God in His infinite power takes away sin and imparts grace. “Although the priestly work of Christ belongs to his humanity, the efficacy of his sacrifice remains inseparable from the divine nature of the incarnate God…” (Cessario, The Godly Image, 147) The sacraments conform us to Christ by their various res et sacramenta (see Nicolas, On the Church and the Sacraments, 217–21). Notably, through the sacramental characters, there is a direct participation in Christ’s priesthood according to the various kinds of character. In other words, the ministerial priesthood and the priesthood of the laity (through their Baptism and Confirmation) are sacramental participations in the priesthood that Christ has by the simple reason of who He is. According to St. Thomas Aquinas (ST III, q. 26, a. 2), the priesthood and mediation of Christ have to do with Him as man in His absolute fullness of grace. As man, Christ shares perfect beatitude with the Father and the ability to die and merit with us. However, the absolute fullness of grace in the humanity of Christ would not be possible unless it were joined to the divine person of the Word by the Hypostatic Union.

It belongs to priesthood to worship God by sacrifice, as well as to sanctify others. That sanctification also involves teaching and governance. The worship of God and the sanctification of humanity involved the restoration of justice lost by original and personal sin. As Fr. Cessario explains:

…Thomas frequently casts new light on the traditional ways of speaking about the incarnation as satisfying God’s justice. Augustine’s speaks about the justice involved in the fact that the incarnate Word destroyed, in the flesh of Adam’s stock, the power of the devil over fallen man. Anselm’s presents Christ’s satisfaction as restoring the broken order of divine justice in the world. Thomas’s discussion of the priesthood and passion of Christ incorporates the main thrust of these traditional approaches to Christ’s satisfaction, with the result that he transforms justice into reverence and worship. The perfect worship of God’s glory remains a priestly act, accomplished in the context of the virtue of religion. (Cessario, <em>The Godly Image</em>, 148)

It is in the context of worship, satisfaction, and sanctification from the priestly incarnate Lord that we move to an understanding of the sacraments in light of the Hypostatic Union.

Incarnational Analogy and the Sacraments

The supreme union of the three persons of God in the one divine nature is the foundational union at the base of all Christian mysteries. The Hypostatic Union is, nevertheless, the Christian mystery that involves the most exemplary instance of how a created principle is joined to, and is instrumentally cooperative with, God. As such, it is an exemplar and cause of other mysteries of union and cooperation with God. “The mystery of the Incarnation will always remain the central point of reference for an understanding of the enigma of human existence, the created world and God himself” (John Paul II, Fides et ratio, no. 80).

St. Thomas explains that the humanity of Christ, as united to a divine hypostasis, acts instrumentally with respect to the divinity to which it is united. The humanity of Christ acts in a singular way, as a conjoined and animate instrument: “The humanity of Christ is the instrument of the Godhead—not, indeed, an inanimate instrument, which nowise acts, but is merely acted upon; but an instrument animated by a rational soul, which is so acted upon as to act” (Aquinas, ST III, q. 7, a. 1, ad 3). 

St. Thomas elsewhere explains that sacraments also work instrumentally in conferring grace, which conferral is ultimately proportioned to the power of God:

But the instrumental cause works not by the power of its form, but only by the motion whereby it is moved by the principal agent: so that the effect is not likened to the instrument but to the principal agent: for instance, the couch is not like the axe, but like the art which is in the craftsman’s mind. And it is thus that the sacraments of the New Law cause grace: for they are instituted by God to be employed for the purpose of conferring grace. (Aquinas, <em>ST</em> III, q. 62, a. 1)

The Hypostatic Union is intimately connected to the sacramental life of the Church because the seven sacraments serve as a kind of participatory extension of the instrumentality of the humanity of Christ. The way the divine power is joined to His humanity in the Hypostatic Union allows for Christ’s humanity and its powers to be in causal conjunction with the divine power. We see this, for example, in the Gospel healings, where Christ’s human words and gestures instrumentally act in the performance of miracles that are manifestations of divine power. This causal conjunction is, again, one of subordinate conjoined instrumentality on the part of Christ’s humanity. That instrumentality serves as exemplar and first in a causal chain allowing the sacraments to be separated instruments of the divine power of Christ. Roger Nutt explains further:

…the participation of the sacraments in the efficient causation of grace is rooted by St. Thomas in the analogical realization of diverse and subordinate forms of instrumentality, each of which presupposes the unique fullness of grace enjoyed by the Incarnate Word. (Nutt, “On Analogy, the Incarnation, and the Sacraments of the Church,” 1003)

St. Thomas explicitly draws out this analogical realization between the instrumentality of Christ’s humanity and the instrumentality of the sacraments:

…a sacrament in causing grace works after the manner of an instrument. Now an instrument is twofold. The one, separate, as a stick, for instance; the other, united, as a hand. Moreover, the separate instrument is moved by means of the united instrument, as a stick by the hand. Now the principal efficient cause of grace is God Himself, in comparison with Whom Christ’s humanity is as a united instrument, whereas the sacrament is as a separate instrument. Consequently, the saving power must needs be derived by the sacraments from Christ’s Godhead through His humanity. (Aquinas, <em>ST</em> III, q. 62, a. 5)

As Roger Nutt explains:

This analogy allows Thomas to trace the causal dependency of the sacraments as causes of grace from the sacramental celebration itself back to Christ’s passion and ultimately to the fullness that he enjoys as a result of the hypostatic union. (Nutt, “On Analogy, the Incarnation, and the Sacraments of the Church,” 1002)

The seven sacraments are, therefore, an analogical extension, through the Church, of the actions of Christ’s humanity that have their ultimate efficacy for salvation in the divine power of the hypostasis of the Word.

Lumen gentium speaks of the way in which the sacraments, specifically Baptism and the Eucharist, join us to the human life of Christ and His saving actions:

In that Body the life of Christ is poured into the believers who, through the sacraments, are united in a hidden and real way to Christ who suffered and was glorified. Through Baptism we are formed in the likeness of Christ: “For in one Spirit we were all baptized into one body”. (1 Cor. 12:13) In this sacred rite a oneness with Christ’s death and resurrection is both symbolized and brought about: “For we were buried with Him by means of Baptism into death”; and if “we have been united with Him in the likeness of His death, we shall be so in the likeness of His resurrection also.” (Rom 6:15) Really partaking of the body of the Lord in the breaking of the Eucharistic bread, we are taken up into communion with Him and with one another. “Because the bread is one, we, though many, are one body, all of us who partake of the one bread.” (1 Cor 10:17.) In this way all of us are made members of His Body, (Cf. 1 Cor 12:27) “but severally members one of another.” (Rom 12:5; <em>LG</em> no. 7)

Sacrosanctum Concilium, the Vatican II document on the Sacred Liturgy, explains the incarnational analogy present in the action of the sacraments to be found in the Church as both human and divine, and in the Church’s liturgical expression:

For the liturgy, “through which the work of our redemption is accomplished,” (Secret of the ninth Sunday after Pentecost) most of all in the divine sacrifice of the Eucharist, is the outstanding means whereby the faithful may express in their lives, and manifest to others, the mystery of Christ and the real nature of the true Church. It is of the essence of the Church that she be both human and divine, visible and yet invisibly equipped, eager to act and yet intent on contemplation, present in this world and yet not at home in it; and she is all these things in such wise that in her the human is directed and subordinated to the divine, the visible likewise to the invisible, action to contemplation, and this present world to that city yet to come, which we seek. (<em>SC</em> no. 2; Cf. Heb 13:14)

The Hypostatic Union provides an exemplar for the union in the Church, which is manifested and caused by the Eucharist. The liturgy also works toward building up, in Christological ways, the perfection and mission of the Church. Sacrosanctum Concilium continues:

While the liturgy daily builds up those who are within into a holy temple of the Lord, into a dwelling place for God in the Spirit, (Cf. Eph. 2:21–22) to the mature measure of the fullness of Christ (Cf. Eph. 4:13), at the same time it marvelously strengthens their power to preach Christ, and thus shows forth the Church to those who are outside as a sign lifted up among the nations (Cf. Is. 11:12) under which the scattered children of God may be gathered together (Cf. John 11:52), until there is one sheepfold and one shepherd. (Cf. John 10:16; <em>SC</em> no. 2)

By virtue of the Hypostatic Union, the humanity of Christ is a conjoined instrument of His divinity and of His divine power that extends into the Church. Beyond establishing sacramentality, the Hypostatic Union also provides a principle of participation for the Church in its teaching and legislative authority and its evangelical and charitable mission (see Journet, The Theology of the Church, 247–253).

The Hypostatic Union and the Eucharist

When the consecration of the bread occurs in the celebration of the Eucharist, the bread changes directly into the Body of Christ by virtue of the sacramental words, and the Body of Christ alone is the terminus or immediate result of the change. Sacraments effect what they signify, and what is signified in the sacramental words of consecration is Christ’s body, given for us in sacrifice. However, the Blood and Soul of Christ are present in the Eucharist because of natural concomitance, or in other words, because what goes together in Christ’s current natural state also goes together when Christ is now sacramentally present. The divinity of Christ is present too because it is hypostatically united to the body and soul of Christ. The parallel is also true for the consecration of the wine into the Blood of Christ. As the Council of Trent explains:

And this faith has ever been in the Church of God, that, immediately after the consecration, the veritable Body of our Lord, and His veritable Blood, together with His soul and divinity, are under the species of bread and wine; but the Body indeed under the species of bread, and the Blood under the species of wine, by the force of the words; but the body itself under the species of wine, and the blood under the species of bread, and the soul under both, by the force of that natural connection and concomitancy whereby the parts of Christ our Lord, who hath now risen from the dead, to die no more, are united together; and the divinity, furthermore, on account of the admirable hypostatical union thereof with His body and soul. (The Council of Trent, Sess. 13, Ch 3, D-H 1640)

The only ways in which God the Son is present by Hypostatic Union are in His natural human presence, on earth two millennia ago and subsequently in Heaven, or through the Eucharist.

Several of the Fathers have argued to the true divinity and unity of Christ based on the Eucharist. Their argument is that if the Eucharist unites us to God, and if the Eucharist is the sacrament of Christ’s body and blood, then a divine person must be in union with the body of which we eucharistically partake. St. Hilary of Poitiers writes:

If the Word has indeed become flesh, and we indeed receive the Word as flesh in the Lord’s food, how are we not to believe that He dwells in us by His nature, He who, when He was born as man, has assumed the nature of our flesh that is bound inseparably with Himself, and has mingled the nature of His flesh to His eternal nature in the mystery of the flesh that was to be communicated to us? All of us are one in this manner because the Father is in Christ and Christ is in us. (St. Hilary of Poitiers, <em>On the Trinity</em> Bk 8, 13, 285)

St. Cyril of Alexandria argues that the flesh of Christ is life-giving only by virtue of its union with the divinity of Christ. He writes:

He is, after all, life by nature, inasmuch as he was begotten of the living Father. And his holy body too is no less life–giving, since it is in some way brought together and ineffably united with the Word who gives life to all. Therefore, it is counted as his, and it is considered to be one with him. He is indivisible after the incarnation except for the knowledge that the Word, who comes from God the Father, and the temple, which comes from the virgin, are not the same in nature. That is because the body is not of the same substance as the Word of God. But they are one by that coming together and ineffable concurrence. And since the flesh of the Savior has become life-giving (in that it has been united to that which is by nature life, namely, the Word from God), when we taste of it, then we have life in ourselves, since we too are united to that flesh just as it is united to the Word who indwells it. (Cyril of Alexandria, <em>Commentary on the Gospel of John</em> Bk 4, Ch. 2, 236)

The Eucharist is the sacrament of Christ’s Body and Blood, and so the sacrament of Christ’s humanity. Nevertheless, it is the sacrament that unites us to the Trinity through the Son and makes us like God because of the Hypostatic Union.

Conclusion: The Humanity of Christ in the Spiritual Life

Because Christ’s humanity is the humanity of God, an emphasis on the humanity of Christ in the spiritual life need not take anything away from our focus on God. In fact, the humanity of Christ is in many ways our entry into spiritual and divine realms otherwise inaccessible. One rich aspect of the humanity of Christ is that it was indwelt by the Holy Spirit in a perfect way (see Lk 4:1). The humanity of Christ is not only hypostatically united to the Word but is the rich field of the Holy Spirit, the Spirit of Christ given to the Church. Moreover, the Son’s Incarnation is to be understood as the Father’s generous providence and special love (see Jn 3:16), to which we respond in grateful worship.

A quotation from General Instruction on the Liturgy of the Hours explains what the Hypostatic Union means for the worship of God:

When the Word, proceeding from the Father as the splendor of his glory, came to give us all a share in God’s life, “Christ Jesus, High Priest of the new and eternal covenant, taking human nature, introduced into this earthly exile the hymn of praise that is sung throughout all ages in the halls of heaven” (<em>SC</em> no. 83). From then on in Christ’s heart the praise of God assumes a human sound in words of adoration, expiation, and intercession, presented to the Father by the Head of the new humanity, the Mediator between God and his people, in the name of all and for the good of all. (no. 3)

It is the prayer of Christ that echoes in the Church. We pray in Christ, with Christ, to Christ, and through Him to the Father. The incarnational and Christological dimension of prayer has ramifications for our personal prayer and devotion. As St. Teresa of Avila says:

And I see clearly, and saw afterward, that God desires that if we are going to please Him and receive his great favors, we must do so through the most sacred humanity of Christ, in whom He takes delight…Let us consider the glorious St. Paul: it does not seem that any other name fell from his lips than that of Jesus, as coming from one who kept the Lord close to his heart. Once I had come to understand this truth, I carefully considered the lives of some of the saints, the great contemplatives, and found that they had not taken any other path: St. Francis demonstrates this through the stigmata; St. Anthony of Padua with the infant; St. Bernard found his delight in the humanity; St. Catherine of Siena, and many others. (St. Teresa of Jesus, <em>The Book of Her Life</em>, 194)

The “Letter to the Bishops of the Catholic Church on Some Aspects of Christian Meditation,” signed by then-Cardinal Ratzinger, states how essential the Hypostatic Union is for developing the life of charity and the vision proper to faith:

<em>From the dogmatic point of view</em>, it is impossible to arrive at a perfect love of God if one ignores his giving of himself to us through his Incarnate Son, who was crucified and rose from the dead. In Him, under the action of the Holy Spirit, we participate, through pure grace, in the interior life of God. When Jesus says, “He who has seen me has seen the Father” (Jn 14:9), he does not mean just the sight and exterior knowledge of his human figure (“the flesh is of no avail,” Jn 6:63). What he means is rather a vision made possible by the grace of faith: to see, through the manifestation of Jesus perceptible by the senses, just what he, as the Word of the Father, truly wants to reveal to us of God. (no. 20, emphasis original)

As Christ is the fullness of the revelation of God in his humanity, and the summation of the saving works of God, so also is His humanity how we ascend to God in charity and true religion.