What is God’s mission, and how are God’s people called to participate in it? It is both surprising and perhaps even concerning how little agreement exists among evangelical missiologists today on such foundational concepts. Some take an expansive approach to argue that the mission of God’s people is synonymous with God’s work in the world, such that wherever Christians partake in what God is doing, they are “on mission.” Others are much more particular, framing it exclusively as an international, cross-cultural, evangelistic endeavour among unreached people groups. Of course, there are many positions and postures between these extremes. Downstream from these debates can be found questions about the role of social action in mission, the balance between its local and global dimensions, and the urgency of the task. Discussions abound regarding the definitions—and even biblical legitimacy—of words such as mission, missions, missionary, and missio Dei. Indeed, evangelical missiological discourse can sometimes be a rather fraught and fragmented space.

In You Will Be My Witnesses, US missiologist Brian DeVries (principal of Mukhanyo Theological College, South Africa) attempts to cut through some of this confusion by distinguishing between “mission” as God’s broad redemptive work in the world, and “witness” as the church’s response to and participation in God’s mission. He argues that God’s people, as beneficiaries of his redemptive mission in Christ, are called to live as witnesses of Christ (noun) in identity and are also called to witness to Christ (verb) in vocation. DeVries explains, “It is helpful, for the sake of clarity, to speak of the witness of the church instead of the mission of the church: the church’s witness serves within God’s mission” (p. 116). In his conclusion, DeVries again argues that “witness is the best term to describe the church’s role in a way consistent with Scripture, which does not combine, obscure, or disconnect God’s work from ours” (p. 244). This distinction represents a bold and largely successful attempt to untangle several knotty missiological debates.

The author builds his case with precision and care through a three-fold structure to the book: (1) an Old and New Testament biblical-theological overview focusing on the redemptive narrative of God’s mission from Genesis 3 to Revelation 22 (chs. 1–4); (2) a concise description of Christian activity in church history highlighting some major themes of Christian witness over the centuries (chs. 5–6); and (3) a theological reflection on the church’s contemporary witness in the world today through the fourfold lens of gospel presence, gospel message, gospel response, and gospel community (chs. 7–10). Keen observers will note that this biblical-historical-praxeological structure echoes that of two of the most important and influential missiological works of recent decades: David J. Bosch’s magisterial Transforming Mission: Paradigm Shifts in Theology of Mission (New York: Orbis, 1991) and Stephen Bevans and Roger Schroeder’s Constants in Context: A Theology of Mission for Today (New York: Orbis, 2004). However, DeVries’s evangelical presuppositions differ markedly from theirs (Protestant ecumenical and Roman Catholic, respectively), and thus so do his conclusions; for whereas they believe that the theology of mission is so contextually bound that its practice should be broadly divergent across time and space, DeVries unashamedly contends that the contemporary witness of the church can be so biblically founded and grounded that its practice should be broadly consistent across time and space.

Readers looking for extensive coverage of contemporary missiological questions, such as people group paradigms, rapidly multiplying church planting movements, or the polycentricity and globalization of mission today, may find little that directly addresses their interests here. However, careful study of the theological principles outlined and explained in this book will provide robust frameworks to discuss these issues and many others faithfully and fruitfully. That said, the third part of the book (on the church’s contemporary witness) at times felt frustratingly non-committal about essential shifts in the twenty-first century, such as migration, majority world Christianity, and the digital revolution; these must inevitably shape—and not only be shaped by—the concept of “witness.” A follow-up volume with more extended attention to these themes would, no doubt, be illuminating, insightful, and important in shaping missiological discourse.

I was especially pleased to see a whole chapter dedicated to “The Mission of the Holy Spirit” (ch. 3). The crucial role of the third triune person in the mission of God and the witness of God’s people are understood in full and rich ways throughout the New Testament, but this has rarely been reflected within Reformed missiology. You Will Be My Witnesses is a much-needed corrective to this detrimental blind spot.

DeVries writes in clear, professional prose. There is little in the way of personal experience, anecdote, or illustration; at times, several substantive topics are addressed within relatively brief sections. Readers would derive the greatest benefit from a patient and studious approach. The engaging study questions at the close of each chapter mean that the book lends itself to communal, small-group study.; potential contexts might include a thoughtful missions committee, a pastor’s fellowship, a mission organization staff team, or a seminary classroom. However, whether read privately or corporately, this book will influence and impact any conscientious reader, and thus, it seems likely to remain relevant and widely studied in the years ahead.