CONSTRUCTING A PUBLIC THEOLOGY: THE CHURCH IN A PLURALISTIC CULTURE. By Ronald F. Thiemann, Westminster/John Knox Press, 176 pp., $14.95 (paper)RONALD THIEMANN, dean of the Harvard Divinity School in Cambridge, Mass., is also an ordained Lutheran pastor. In his highly compressed book, "Constructing a Public Theology: The Church in a Pluralistic Culture," he makes a strong case for a more meaningful engagement of the religious conscience of Christians with the broad public issues of the day. The American democratic system, he notes, "presupposes a virtuous public life," but the cultivation of public virtue is left to the individual. It is the duty of the churches, in his view, to contribute to the pluralistic conversation in American society. This contribution should not, in the main, consist in the support of specific policies or pieces of legislation. It lies more in the realm of using our religious resources to ask ourselves what kind of people we are, what America's role in the world sho uld be at this moment in time, and, of course, in addressing issues of fairness and justice in specific public-policy measures. Thiemann finds an "odd dichotomy between religion's rhetorical power and its political impotence." He is not looking for the church's entry into politics as such, but for evidence that the church's teaching has penetrated the thinking of those making policy decisions. The entire book seeks ways to make religion come alive for the practicing individual in a manner that encompasses what he does in his public activities as well as private. Thiemann is not alone in noting the growing separation between religion as a kind of private matter and the secular world of business and politics. The reason for it, he thinks, is in large part that many of the churches have lost their roots. In an interview with him, I asked if this meant simply going back to the Bible stories and to their application to public life. It is much more than that, he says. "The churches must affirm their continuity with the past through a critical appropriation of their tradition." This critical appropriation takes place as they operate with an awareness of life today, of the general outlook of mankind. The biggest challenge for modern theology, he says, "has been to restate the Christian gospel under the changed conditions of the modern world; that is, in an intellectual and cultural atmosphere in which the reality of God, and perforce of God's grace, has been decisively questioned." Much of the church, he says, - and particularly the traditional mainline Protestant denominations - has lost its sense of identity. In so doing, it has lost its sense of what it should be doing in society. With the correct sense of mission restored, it will be able to steer a middle path between the extremes of the "politicalization of worship" and a complete separation from public life. In a chapter on the Swiss theologian Karl Barth, he notes the criticism Barth received for his theological language not making sufficient contact with the secular world. In defense of Barth, Thiemann writes: "Because [Christian] language describes our common world of experience, it must be related to other forms of human discourse, but the terms of that relation must always be ruled by the logic of the Christian gospel." Thiemann also calls for an attempt to find larger areas of commonality. There are basic values that we can still identify in our democracy, he believes, even while we accept the reality of our increasingly pluralistic society. Among the churches themselves he would also like to see a greater search for commonalities. He likens this to a picture with numerous overlapping circles. The circles never merge into a single unity (nor would that be desirable), but as we look at the overlaps we find many areas that could have a common shading. He also notes that the most difficult bridges to make are often with those with whom we disagree in our own denominational outlook. The Missouri Synod of the Lutheran Church, with which he was formerly associated, underwent a schism a decade or more ago, and the Southern Baptists have been having the same experience more recently. Yet the church, beyond representing a beacon of hope in modern society, must itself become a model for "a way of life that affirms commonality in the midst of diversity." The ideas in this book deserve the consideration of all those who look for a better anchoring of the debates over public policy in our strongest religious traditions.