According to the Bible, eternal life means knowing God (John 17:3). The Bible also tells us that it is those who know their God that stand firm (Daniel 11:32). But how much do we truly know about God?

According to Robert Letham, many Christians in the West have a very poor view of God, confessing Him to be a Trinity, but having failed to think through the implications of this for doctrine, worship and life. We ought to be grateful, therefore, that this book has been written by a leading theologian in the Reformed tradition, to help us appreciate the glory of our Triune God.

Although some chapters are heavy going, this remains a readable, comprehensive and definitive study of the doctrine of the Trinity in the unfolding revelation of Scripture, in the maturing reflection of the church’s history, in systematic theology, and in the life and witness of the evangelical community.

Letham’s discussion of the revelation of God in Scripture is thorough, beginning at the beginning, with the statements of Genesis regarding creation and the nature of man. We are reminded that the vocabulary of Genesis ‘attest[s] a plurality in God, a plurality later expressed in the doctrine of the Trinity’ (p20).

Equally thorough are the treatments of the Gospels, with their revelation of the deity of Jesus Christ, so crucial to the unfolding of the revelation of the nature of God as Triune. And have you ever noticed that not only does the New Testament teach a Trinity, but couches much of its teaching in ‘triadic’ ways? The application of this to the letter to the Ephesians (pp73-85) is worth the price of the book.

The discussion of historical development is extremely. In them we travel from the second century apologists to modern contributors like Tom Torrance, with special emphasis – as one would expect – on Arius, Athanasius, Augustine, the Cappadocians, the filioque, Calvin, Barth, Pannenberg and Lossky.

A chapter on the Trinity and the Incarnation carefully guides us through the issues surrounding the relationship between the tri-personal God and the two natures of the Second Person. Might any of the Three have become incarnate? Mysteriously, the incarnation of the Son reveals the whole Trinity. Gloriously, ‘the Son’s submission to the Father is compatible with his full and unabbreviated deity’ (p402). These are the questions that begin and end in mystery.

Yet they also led to worship, prayer and praise, to which Letham devotes another chapter, charging Western Christianity with worship with is not explicitly trinitarian at all. John Owen’s discussion of communion with the Triune God is (helpfully) taken as a model: worship can only take place on the basis of a trinitarian salvation. The final chapter on the Trinity and Persons explores the nature of relationship, and suggests that this brings us to the heart of the Gospel.

This book deserves wide circulation and careful reading. If nothing else, it will make us examine our Christian lives and church practice, and lead us to ask just how much – or perhaps how little – the doctrine which we profess informs and influences the way we live out our Christian lives.