Review: The Eternal Son By Robert Letham

by on November 13, 2025 | Comment

Jesus Christ is the center of Christianity. Our faith is named after him. One of the crucial questions then must be: Who is Jesus Christ? In his new volume, The Eternal Son, Robert Letham tackles this question about Christ’s identity.

This book is the second in a planned trilogy about each person of the Godhead. The whole trilogy serves as an expansion to his award-winning book, The Holy Trinity.1 His initial volume in this series, The Holy Spirit, was an in-depth exploration of the Holy Spirit, looking at both the Spirit’s person and work.2 In that volume, Letham considered the topic from the vantage of church history and from a redemptive-historical survey of Scripture.

The Eternal Son includes a different approach in two respects. First, Letham focuses almost entirely on the person of Christ. Although he briefly discusses Christ’s work, overall, this book has entirely in view issues around Christ’s person as God the Son, eternally dwelling in the Godhead, and then Christ’s two natures as God the Son became incarnate. Letham has written another complete book about the other side of Christology, The Work of Christ.3

Second, Letham structures this book mainly in terms of historical development. In The Holy Spirit, he switched modes to discuss exegetical aspects of the Spirit in redemptive history from an explicitly biblical point of view. In The Eternal Son, he omits the redemptive-historical perspective. Good reasons may well undergird that decision, since his focus is on strictly the person of Christ. The Spirit’s work brought in specific redemptive-historical considerations. Christ’s two natures, however, do not undergo any development (aside from, in a limited sense, his transition from humiliation to exaltation).

Letham’s book is in many ways a tour de force as a guidebook for navigating issues in classical Christology. Having structured his work according to the various historical developments concerning the ecumenical creeds and later theological reflection, he leads us through the concerns that motivated each of the debates, creedal conclusions, and later matters of consensus.

This historical approach provides helpful insight to make us appreciate the careful formulations we have in the creeds and in later tradition for protecting good Christology. We easily enough see what we say about Christ’s person in the creeds and according to various pivotal theologians. In addition to seeing what we say, as Letham winds his way through the controversies about Christ’s person, we learn more fully why we say it. Letham is detailed and careful as he explores ancient sources that illumine the steps for clarifying the church’s thought about how best to explain how God the eternal Son assumed a human nature for the work of redemption.

Several strengths mark this book. First, Letham addresses both the Son’s eternal personhood and his incarnate state. He deals with eternal generation especially, followed by extensive investigation through most of the chapters about the relation of the Son’s divine and human natures.

Second, Letham is an excellent guide through lots of historical issues. He works through many primary sources and has a clear grasp of original languages as he interacts with Latin, Greek, and French sources. This book is a solid grounding in traditional discussions.

Third, Letham highlights several doctrinal concerns that we should have on our radar today. The first that he addresses is the modern trend toward kenoticism. In this issue, kenotic Christology argues drawing from Philippians 2:7 that the Son gave up divine attributes as he became human. On one hand, Letham provides traditional rationale for rejecting this school of thought. On the other hand, he also makes us aware of recent ways this error has come to new prominence again in scholarly circles.

The second doctrinal lacuna that Letham helpfully tackles is how the incarnate Son relates to the Spirit. A rising trend has suggested that the incarnate Son depended on the Spirit because of his humanity’s limitations. By suggesting that Christ performed miracles and other works entirely by depending on the Spirit, this view contrasts with the traditional view that Christ’s miracles and other works exhibit his divine identity. Often, John Owen is invoked as a proponent of this view.

Letham argues, as I have as well, that this view misunderstands Owen and implies significant errors.4 Although acknowledging some truth to the position, he shows that the primary reason for the Son’s dependence on the Spirit is not because of his humanity’s limitations but because of his divinity. More specifically, God the Father, God the Son, and God the Spirit necessarily perform all their external works inseparably. The Father works through the Son by the Spirit. For Christ, he did not depend on the Spirit primarily because his humanity needed help. He depended on the Spirit primarily because God the Son always works by the Spirit.

Letham identifies the problem built into the newer view, which is to make Christ more of an example than Savior. My concern has been the same. When Christ depends on the Spirit because of his humanity’s limitations, he becomes an example for us to depend on the Spirit in the same way. It diminishes the significance of God the Son acting according to a true human nature. The person of Christ remains God the Son, who always works by the Spirit even when operating according to his human nature.

Despite this book’s great strengths, it also has a few weaknesses. First, Letham has historically been critical of the traditional Reformed doctrine of the covenant of redemption. In this book, he seems less critical. At the same time, he is vague about whether he affirms it. He rightly outlines some premises of traditional Trinitarian and Christological doctrine that must be upheld as we formulate the covenant of redemption. The implication may be that he still thinks this reconciliation is unlikely. His appreciation for Karl Barth, in multiple places but especially here, raises questions and may explain his critical approach to the covenant of redemption.

Second, more exegetical discussion could have bolstered the clarity for Letham’s arguments. He excels in threading the needle through theological issues and explaining the rationale for where the tradition landed. More positive exegetical explanation would have made this book a definitive resource in orthodox Christology.

Third, Letham’s writing style suffers at various points. He often shifts to quoting extensively from secondary sources to make points when his words with a footnote would have sufficed and kept the flow of thought moving more smoothly. Some sections even become massive sections of quoted text merely threaded together. Quotes should serve as the basis for analysis, not as a substitute for the author’s own words. The publisher seemed to miss several places where formatting became inconsistent too.

Despite these caveats, Letham’s new book is one of his best. It is a shining display of research into the Christian tradition with a mastery of theological implications. It is more than worth reading.

Notes

  1. Robert Letham, The Holy Trinity: In Scripture, History, Theology, and Worship, Revised and Expanded (P&R Publishing, 2019).
  2. Harrison Perkins, “Review: The Holy Spirit By Robert Letham,” Heidelblog, September 14, 2023.
  3. Robert Letham, The Work of Christ (IVP Academic, 1993).
  4. Harrison Perkins, Reformed Covenant Theology: A Systematic Introduction (Lexham Academic, 2024), 169–70n44.

©Harrison Perkins. All Rights Reserved.

Robert Letham, The Eternal Son (P&R Publishing, 2025).

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