If we are all adopted sons, then we are all part of the blood royal. We are royalty with Him—not by physical descent, but by our union with Christ, the true and natural Son.

This article from The Aquila Report is a critique of a book written by David Garner called Sons in the Son, which was published in 2016. I have never read the book myself, but I have ordered a copy due in part to the many endorsements it received. The book has a foreword by Sinclair Ferguson, and the endorsements included J. I. Packer, Joel Beeke, Richard B. Gaffin Jr., Harry L. Reeder III, and Guy Prentiss Waters.

This critique by Dr. Robert Letham and Dr. Lane Tipton is highly academic and employs precise theological terminology. I found myself having to consult definitions simply to work through it.

The Letham–Tipton article does an excellent job defending classical Chalcedonian Christology, and I am thankful that the church has such able defenders of orthodoxy who know the proper terminology to discuss these matters.¹ There was a time when these categories were widely understood throughout the church. Today, however, much of that vocabulary has been lost, making discussions like this difficult for ordinary readers to follow.²

I have included a dictionary of the key terms in an appendix. In several places, the dictionary also functions as a running commentary on the article itself. As I worked through the discussion, I found myself having to look up many of these terms just to ensure I understood what was being argued. You can find the full article at The Aquila Report here. ³

If I had to summarize the article’s main point in plain English, it would be this:

Dr. Robert Letham argues that Christ cannot be an adopted Son because adoption belongs to persons, not natures. If Christ were adopted, either the eternal Son would enter a new filial relationship with the Father (threatening divine immutability) or Christ’s humanity would function as a separate personal subject (tending toward Nestorianism). Thus, Jesus Christ is eternally the natural Son of God and never becomes an adopted Son.

Dr. Lane Tipton puts it this way: Moreover, the messianic sonship of Jesus distinguishes the Redeemer from the redeemed; it at no point subsumes their identities under a single filial category. Christ is the incarnate Mediator, the anointed Son sent by the Father to accomplish redemption for those who are adopted in him. His filial identity is therefore not derivative or redemptive, but natural and eternal. The mediatorial office rests entirely upon his identity as the eternal Son. Precisely because he is the natural Son, he can communicate adoptive sonship to others through union with himself. The resurrection, therefore, does not transform Christ into an adopted son alongside believers; rather, it publicly declares and enthrones the incarnate Son as the exalted Messiah who secures and bestows adoptive sonship upon his people.

Given that this article in The Aquila Report has ably defended the Son’s uniqueness, I want to examine the question from the perspective of the “sons.” What does it mean for believers to participate in union with Christ? How do the Chalcedonian boundaries frame that discussion? If Christ is the natural Son and we are adopted sons, what exactly do we participate in, and what distinctions must remain in place if those boundaries are to be preserved?⁴

Ontological Union

This is probably the first place to start when talking about the nature of our participation in the body of Christ. From the discussion in the Letham–Tipton article it should be clear that the incarnation is unique. Before the incarnation the Son was asarkos—without flesh. After the incarnation he was ensarkos—the Word made flesh. He took to himself a true human nature, but he did not absorb that human nature into the divine nature. Chalcedon is the operating grammar here: one person, two natures, without confusion, without change, without division, and without separation. This hypostatic union is unique and unrepeatable.

How then do the “sons” participate in Christ? They do not become one with Christ’s human nature. They are adopted sons, not natural sons. The sons participate in Christ, but they do not become part of Christ’s hypostatic union or personal identity. They remain human persons united to him by the Holy Spirit.

This boundary is important. Whatever union with Christ means, it cannot mean that believers are physically incorporated into Christ’s human nature or absorbed into his personal identity. The church has often used very strong language about participation, communion, deification, and union with Christ, but no orthodox tradition teaches that believers become part of the hypostatic union itself. The incarnation happened once. The Son became man. We do not become part of the God-man.

The Chalcedonian boundary remains in place. Christ remains the natural Son. We remain adopted sons. Whatever participation means, it must preserve that distinction.

Ecumenical Agreement

At this point there is remarkably little disagreement among the major branches of the church. Roman Catholics, Eastern Orthodox, Lutherans, and the Reformed all affirm the uniqueness of the hypostatic union. They may differ somewhat in how they describe the participation of the sons, but they do not teach that believers become part of Christ’s hypostasis.

Sometimes theologians speak of the church as an extension of Christ’s presence in the world or even use language that sounds incarnational. However, such language is not meant literally. The church is not a continuation of the incarnation, nor are believers incorporated into Christ’s hypostatic union. The incarnation happened once and belongs uniquely to the eternal Son. Whatever participation, communion, union, or deification means, it must preserve the distinction between the natural Son and adopted sons.

In that sense, Chalcedon functions as a guardrail for the entire discussion. The real debate is not whether believers participate in Christ, but how they participate in Christ while remaining within those boundaries.

If believers do not participate in Christ by becoming part of His hypostatic union, then how do they participate? The New Testament repeatedly answers: by union with Christ through the Holy Spirit. We remain distinct human persons, yet we truly share in His life, His inheritance, His kingdom, and the adoptive sonship that He has secured for us by grace. The precise nature of that participation has been described in various ways throughout church history and deserves further examination. That question will be my focus in future articles as time permits.⁵

The Sons of David and the Blood Royal

This article in The Aquila Report has certainly sparked my interest in a further study of the doctrine of adoption. The highly technical nature of the article has helped me grow in my understanding of Jesus Christ. I needed a refresher on Christology. The article did something even more—it made me want to know more about our adoption in Christ and what that means on a day-to-day basis. I look forward to reading this book, although with caution about the Christological boundaries.⁶

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