This monograph by John Flett is a seminal contribution not only to missiology but also to theology as a whole, with implications far beyond its immediate remit. Flett examines the use of the concept of Missio Dei, now almost 60 years old, in contemporary missiological use. The received understanding of the history of the use of the term is that it was an attempt to recast the theological basis of ‘overseas missions’, and then ‘mission’, within a supposed trinitarian framework. However, the varieties of constructions used had either the intended or unintended consequences of creating a ‘container term’ which blurred more than clarified. A historical line was assumed which began with Karl Barth's 1932 lecture, ‘Die Theologie und die Mission in der Gegenward’, and then passed on through Karl Hartenstein, a dialectical theologian and influential international mission administrator, as the Basel Mission Director to the International Missionary Council at Willingen, Germany, in 1952, and so into the wider ecumenical movement.

Flett engages with careful historical and theological analysis of the documentary evidence. He examines two issues running in parallel. First, he cautiously and critically deals with the historical material. Here he provides us with the analysis of an enormous amount of original material, particularly his work on Hartenstein and Knak, in addition to the classically received documents. What he does is to try historically to reconstruct the uses of this fluid term Missio Dei in the development of missiology, particularly from the 1920s. This use largely came from a background of attempts by the churches and missionary societies to distance themselves from colonial attitudes towards missions. Missio Dei, with all its ambiguity, seemed to be the theological way out for churches intent on freeing themselves from colonial perspectives, which in their worst instances painted Christianity as little more than as giving a veneer to European, and in particular German, understandings of providing cultural improvements to indigenous societies. These perceptions were some of the most severe elements of what Barth criticised in Kulturprotestantismus. In German missiology this is seen in some of the assumptions in the writings of Julius Richter, Bruno Gutmann and Christian Keysser, which, although apparently useful in missiological methodologies, nevertheless produced a romanticism of European cultures quite inimical to trinitarian faith.

Second, there is the central theological issue of the nature of the Triune God. Fundamentally for Barth ‘missionary’ or ‘sendingness’ is of the very nature of the Triune God. The mystery of the Triune God is that God is not God apart from, or separate from, humanity, but rather that God's very life intersects with the unity of the Son of God with humanity. At the heart of the Christian faith is expressed the fact that God is not to be alone in celebrating the wonder of God's inexpressible love for humanity. In this sense the Triune God is missionary. Over against Barth's position are a variety of positions which have actually been behind much of Missio Dei theology, which is the position that God's missionary activity is the second step coming from the nature of the Triune God. In other words, this missionary activity of God is not of the very being of God but rather a consequence. Related to these two positions is the discussion as to the nature of the ‘point of contact’ or ‘connection’ (Anchnüpfungspunkt) between the Triune God and humanity. Here it might also have been helpful to have looked further at the Dutch discussions.

On the basis of this historical and theological analysis, Flett goes on to construct a revision of trinitarian Missio Dei theology. He maintains that mission or witness is an integral part of the being of the Triune God, and that the church must reflect this fact by at all times being a missionary community in its very nature. Flett works this out in terms of the joyful life of the Christian community, with emphasis laid upon its communal life of service rather than on ecclesiastical ordinances.

This is a book of great richness. No review can give justice to the very great number of insights given as Flett works through his historical and particularly his theological arguments. As a single example, his careful linguistic and translation research on the texts of Barth and his contemporaries is in itself an enormous contribution to systematic theology. Both his historical and his theological work sheds significant new light on the central missiological and ecclesiological discussions of the ecumenical movement and on what often lay behind the argumentation of many of its major proponents. The implications of what he cogently argues need to be carefully assessed by both theologians and missiologists, particularly in the light of his critique of their unconscious assumptions.

This work is a brilliant and pivotal contribution both to missiology and to theology in general.