Letham is exploring what we can learn of the doctrine in Scripture, in history and in theology. In this light, one could see the focus of his work to be theoretical more than practical, more constructive and aimed at making doctrinal connections rather than practical applications.
Additionally, Letham's focus in history and theology is limited to primarily Reformed theology (as one might expect in a book published by P&R) though he picks conversation partners like Hieronymous Zanchius, Amandus Polanus, and Rowland Stedman who are not quite the mainstream names that Calvin, Luther, and Bavinck are. Granted, the latter authors are given more space to share their ideas, but since Letham's overall objective is to trace the doctrine from Scripture through history, he needs more than just the big names to show its development.
To give you an idea how the Letham's thought flows in this book, chapter one begins with creation. Here, Letham sees union with Christ resting "on the foundation of man's nature as created," and "seen in the light of God's end purpose for man" (p. 18). Indeed, as the chapter opens, he says "union with Christ rests on the basis of the creation of man to be compatible with God" (p. 9). If God and man are ultimately incompatible, there is no possibility of a union with Christ.
What I found particularly striking in this chapter was Letham's contention, following Paul, that "Adam was created in Christ and then fell from that condition, but now, by grace, we are being renewed in the image of God, in Christ the second Adam, and thus in knowledge, rightouesness, and holiness" (p. 14). Or in other words, the union with Christ is restoring a union that was God's original intention in the creation of Adam. I think I had latently understood this, but I just hadn't connected Adam's creation in the image of God to our re-creation in the image of Christ, much less how that connected to union with Christ as a doctrine.
To further flesh out this connection, Letham moves from creation to incarnation in chapter 2. If the possibility of our union with Christ is illustrated in creation, the "basis of our union with Christ is Christ's union with us in the incarnation" (p. 21). As Letham continues, "We can become one with him because he first became one with us. By taking human nature into personal union, the Son of God has joined himself to humanity," and then later summarizes, "since Christ has united himself to us in the incarnation, we can be united to him by the Holy Spirit" (p. 40). In order to ground these points more fully, the bulk of chapter 2 is composed of an excursus on the development of Christological thought up to the 2nd Council of Constantinople. Considering the space Letham works with, I thought he did an excellent job of summarizing some of the major developments in the church's understanding of the Incarnation.
Chapter 3 then moves forward to discuss Pentecost. Building on the initial foundation of God and man being compatible (chapter 1) and Christ's union with humanity in the incarnation (chatper 2), Letham observes that "Christ, the eternal Son, having united human nature in himself, now unites us with himself by the Holy Spirit, as the Spirit draws us to him in faith" (p. 54). Because of this, "the Holy Spirit enters, indwells, saturates, and pervades countless human persons and so brings them into union with Christ the Son." This then completes Letham's groundwork on the foundations of the doctrine of union with Christ, and so that the next three chapters can unpack the content of that union.
First, in chapter four we see that union with Christ means that Christ is our representative before the Father. It is in this and the next two chapters that Letham does more historical survey work. While this chapter discusses the relationship of union with Christ and the doctrine of justification, many readers may be disappointed that Letham doesn't interact with any current trends in the discussion of justification. However, given his overall purposes and focus, this shouldn't be viewed as a deficit of the book itself since it falls outside its scope. As Letham himself notes, "the purpose of this book is to present a picture of how I understand union with Christ to relate to the broader theological context" (p. 82). In that light, Letham provides this summary of Christ's representation of us in the union:
Union with Christ is based on Christ's being our covenant head and is established by his sharing our nature
Since he is our head and representative, who shares our humanity, all that he did in his earthly ministry was done as a substitute and representative.
Since he share our nature, and since the Holy Spirit unites us to him, all that he did and does is in union with us.
This union is the ground of our whole salvation, justification, included. We receive a right status before God, since we are incorporated into the Son of God himself.
One analogy Letham uses to capture some of this is that of a team captain. When the captain of a team scores a goal, or when the quarterback of a football team throws a touchdown pass, it counts for the whole team. While imperfect, the analogy does capture much of what is meant by Christ being our representative.
Chapter 5 shifts the focus from Christ as our representative to the transformative effects of our union with him. This chapter covers perhaps the most ground, discussing everything from sanctification in general, to theosis, to the ordo salutis, to extensive discussion of Calvin on the Lord's Supper. In the end, Letham concludes with 10 theses on union with Christ and our transformation:
The union we enjoy with Christ is more real and more fundamental than the union we have with members of our own bodies
This is not a union of essence - we do not case to be human and become God or get merged into God like ingredients in an ontological soup. This is not apotheosis.
We do not lose our personal individual identities in some universal generic humanity.
Union with Christ comes to expression in, and is cultivated by, the Word and sacraments.
The body and blood of Christ are not materially, corporeally, or physically present in the Lord's Supper.
In the Lord's supper we are lifted up by the Holy Spirit to feed on Christ.
We are not hypostatically united to the Son.
We are united with Christ's person.
It is effected and developed by the Holy Spirit through faith.
It will eventually lead to our being "like Christ."
In some ways, this chapter is the kind of climax to the book with chapter 6 being more like a denouement. However, it is in the final chapter that Letham turns his focus to union with Christ in death and resurrection. Because of our union with Christ, we are united with him in his death and burial, as well as his resurrection and ascension. As Letham notes, "the resurrection of Christ and our resurrection stand or fall together" (p. 135). Because of this, "at our resurrection there will be the same engagement of the whole Trinity as there was when Christ himself resurrected. The two resurrections are identical in theological terms as well as identical in the outcome they produce" (p. 136). Christ's resurrection is then paradigmatic and "shapes the whole of salvation in union with Christ" (p. 137). As Letham concludes, this is found in already-not yet expression in our baptism.
And with that, Union with Christ comes to an end. This may be perhaps my only real quibble with the book. While Letham's style of writing is clear and crisp and his insights penetrating, the book seems to come to a rather abrupt end with no real conclusion beyond just a short summary statement at the end of chapter 6. I would have liked the book itself to be longer, but it's relatively short length (just over 140 pages) definitely makes it more accessible. Though it may be theologically dense at times, most people would do well to spend some time digging through the treasures Letham has gathered concerning our union with Christ.
Particularly this time of year, we do well to remember that Christmas is a celebration of the Incarnation, as we saw above, it is precisely that Incarnation that makes our union with Christ possible. And it is this union with Christ that restores our communion and fellowship with God. We do well to emphasize that Jesus came to save us from our sin, but what we miss sometimes is that he came to unite us to himself and to bring us back into our originally intended communion with God. As this week leading up to Christmas progresses, I'll have more to say on this, including another review of book with the same title as this one.
[A review copy was provided to me by the publisher]
