A sweeping survey of the biblical data concerning the question of our union with Christ would produce such a vast amount of conclusions that apart from a systemic definition, the pertinent implications could very easily be over looked. Grudem’s systematic theology offers one such definition narrowing the field to four relational categories. His definition is as follows: “Union with Christ is a phrase used to summarize several different relationships between believers and Christ, through which Christians receive every benefit of salvation. These relationships include the fact that we are in Christ, Christ is in us, we are like Christ, and we are with Christ.”
Given therefore, the breadth of this topic I wish to limit my contribution to the board to the fact that we are in Christ. And more particularly, the covenantal-identification aspect of our being in Christ (or better, under Christ); a perspective tempered in the flames of the Reformation, commonly known as federalism (or: representative headship, federal headship, etc). I will restrict this perspective to only two observations, they will be: (I) the eternal roots of this union,and (II) the necessity of the Incarnation for this union.
I. THE ETERNAL ROOTS OF THIS UNION
This section will examine two facets of the eternal rooted-ness of our union with Christ; (A) the eternal plan of God, and (B) the eternal person-hood of God. These two factors describe the essence of our union with Christ and offer the most absolute assurance of the union’s reality. These both swing upon God’s faithfulness to himself.
A. Our union with Christ in relation to the eternal plan of God is perhaps most emphatic in Paul’s letter to the Ephesians’—chapter one. Straight out of the gate in this letter Paul makes haste to tells us that God chose believers in Christ “before the foundations of the world” (Eph 1:4). Furthermore, those that are found “In Christ” have been predestined to be so in order to obtain an inheritance and live to the “praise of his glory;” all of which is based on nothing other than God’s own eternal purpose and sovereign will (1:11-12; cf. Rom 8:28—30; II Tim 1:9).
Hence, our salvation and all that is bound up in our union with Christ can be understood as a reality that has its roots in eternity past. For eternity, in the mind of God, those predestined in Christ have always been thought of as in union with the Son. Christ, therefore, being the head, is a representative of a new, called out humanity that lives to the praise of his glory. Although, God’s thoughts are what determine the extent and bounds of realty, the reality of our union with Christ is actualized in history through the individual’s responding to the Spirit’s call, and appropriating a position in and under Christ’s headship by personal faith in his redeeming work as the second Adam (“last Adam” per KJV; I Cor 15:45). Thus, through natural generation (i.e. birth) each and every member of Adam’s race stands as a condemned sinner before their Creator. Under the covenant headship of Adam we are “by nature, children of wrath” (Eph 2:3). However, as our union and solidarity with Adam is confirmed over and again through our “actual sins,” so too is our union with/in/under Christ’s headship is realized and confirmed by our “actual faith” and a life of progressive growth in grace (Rom 6:14). Therefore, “God’s firm foundation stands, bearing this seal: ‘The Lord knows those who are his,’ and ‘Let everyone who names the name of the Lord depart from iniquity’” (II Tim 2:19).
B. Our union with Christ and the union/unity of the Godhead is explicitly linked in two passages in the Gospel of John. Both are set within Christ’s most intense earthly communion; the first, horizontally, with his fear-filled and bewildered disciples (Jn 14:18—20); the second, vertically, as he sanctifies himself and his followers before the Father (17:21—22). These two pericopes, both containing the concept of the Godhead’s Ultimate union as the foundation of our union in Christ, sandwich one of Jesus’ most lengthy discourses on the topic of the mutual “abiding” or union of he and his disciples (Jn 15:1—17).
In the first (Jn14:18—20) Jesus promises the desperate disciples that he will not leave them orphans, but that he will come to them, love them, and manifest himself to the one who loves him (vv.18, 21). Now, the context seems to be anticipating the day of Pentecost, when the “Helper” (i.e. Holy Spirit, v. 16) does indeed come and dwell in them (v. 15—17; cf. 16:4—15). If this is the case the only way to render Jesus’ promise sensibly is to assume that he equates the Spirit’s coming as being in reality his own presence. It is amidst this emphasis on the unity of the Godhead that Jesus says, “Because I live, you also will live” (v. 19c), a polar contrast to “in Adam all die” (I Cor 15:22a).
The same analogous parallel between the unity of the Persons of God and believer’s union in Christ is also met out in Jn 17:21—22. Both of these passages demand our recognition of the “mystery” of our union with Christ.
Thus, to summarize, all believers, individually and corporately, for all eternity in the immutable knowledge of God, have been in union with Christ. This reality in the plan of God is actualized in history through the individual believer’s appropriating faith in Christ as their redeeming covenant head; hence, moving from one Adam to the last Adam. The mysterious nature of our union with Christ has for its archetype or essence the pattern of the unity of the Godhead. This is not to embrace an irrational view of the matter, but a humble recognition that it is perfectly coherent in the mind of God although human reason cannot grasp the concept exhaustively—though truly, just not fully.
II. THE NECESSITY OF THE INCARNATION FOR THIS UNION
This point can be most readily grasp by understanding the fact that in the course of human history God has dealt publicly (e.g. globally, cosmically, eschatologically, in terms of the whole of humanity) with only two men—first in Adam and finally in Jesus Christ. Therefore, every man, woman and child stands in and under one of these respective representative heads. And because of the Fall—one is the head of death, and because of the Incarnation—the other the Head of Life. Thus, the miracle of the Incarnation was utterly necessary for God to reverse the curse of the fall of man. Man needed a New Head to represent him before the Creator, this Man must be of an incredible sort—he must be the GOD-MAN.
A. The solution to the dilemma of eschatological humanity ‘in Adam’ is inexplicable apart from GOD becoming that Man, that Head, which would solve it and create a New Humanity ‘in union’ with himself. In the last 1700 years few if any has demonstrated the air tight logical behind the “Divine necessity” of the Incarnation better than the young brilliance of St. Athanasius (4th cent). The following quote is a bit lengthy, yet worth its weight in gold. He explains:
“You must understand why it is the Word of the Father (the Son), so great and so high, has been made manifest in bodily form. He has not assumed a body as proper to His own nature, far from it, for as the Word He is without body. He has been manifest in a human body for this reason only, out of the love and goodness of His Father, for the salvation of us men. We will begin, then, with the creation of the world and with God its maker, for the first fact you must grasp is this: the renewal of the creation has been wrought by the Self-same Word Who made it in the beginning. There is thus no inconsistency between creation and salvation; for the One Father has employed the same Agent for both works, effecting the salvation of the world through the same Word Who made it in the beginning.”
Athanasius goes on to narrow his broad use of “creation” to that of Adam; that is, to fallen man. The Fall and corruption of man in Adam in conjunction with Yahweh’s faithfulness to his own covenantal terms (Gen 2:15—17) created a dilemma of infinite proportions; one that would require an Infinite Solution. The New Head of humanity would require divinity, for only God himself owns the unlimited capacity to absorb death and propitiate himself of the unbounded corruption of humanity under the headship of Adam. Thus, for a restored union with the Creator, the divine side of the hypostatic union in Christ is demanded for solidarity and communion to and with God himself. Therefore, Jesus, as our representative Head, had to be the God-Man. The first man is from the earth, the Second Man is from heaven (I Cor 15:47).
B. Having then, man’s solidarity with God ‘in union with Christ,’ touching his divine nature, the Incarnation also provides Christ’s solidarity with the eschatological humanity by means of his own humanity. As we have seen, one side of the equation demands that the new humanity’s Head be on the one hand deity; however, because it is Adam and his progeny that has offended God, and of course, not God himself, the New Head of man must also be just that—a Man—in order to make union with himself possible.
The whole of Paul’s argument in Rom 6 swings on the necessity of Christ’s humanity, for on the cross and in the resurrection Jesus was representing humanity before its Creator. It is also Christ’s humanity that allowed God to reckon our sins to Christ, legally considering them his own (II Cor 5:21; I Pet 2:24; cf. Is 53:6). Adam’s one act brought death to all he represented; all of mankind, so death reigns in and through one man and comes to all under his headship, likewise, because of his humanity, Jesus’ righteous act gives life to all he represents (Rom 5:12ff), therefore, by the grace of God Jesus tasted death for everyone who is in this union with him (Heb 2:9). “God thought of us as going through everything that Christ went through, because he was our representative.” Thus, Jesus had to be the God-Man to stand as our representative Head.
Therefore, in the Incarnation we have union with the One who is God on the one hand; infinitely able to bear the curse for all he represents, and Man on the other; able to identify with, in solidarity through his own humanity, the ones that he represents. When reading Rom 5, it is tempting to understand Christ dying for us in purely substitutionary terms, in this context however (namely vv. 12ff), Paul is presenting Christ in his office of representative. “If he died on the cross as our representative, and that death was accepted, then it was accepted as our death, so that when he died, we died. He was an effective representative!”
Given then, Rom 5; 6 and I Cor 15, we could in one sense summarize Paul’s understanding of Christian redemption as man being translated from “in Adam” unto death to “in Christ” unto life, and this saving moment being, by faith, a shift in one’s headship or representative—from a union with death to a union with Life.
I call upon You, Lord, God of Abraham and God of Isaac and God of Jacob and Israel, You who are the Father of our Lord Jesus Christ, the God who, through the abundance of your mercy, was well-pleased towards us so that we may know You, who made heaven and earth, who rules over all, You who are the one and the true God, above whom there is no other God; You who, by our Lord Jesus Christ gave us the gift of the Holy Spirit, give to every one who reads this writing to know You, that You alone are God, to be strengthened in You, and to avoid every heretical and godless and impious teaching.
St Irenaeus of Lyons, Against the Heresies 3:6:4
St Irenaeus of Lyons, Against the Heresies 3:6:4