This is an excellent resource that presents a fresh approach to its topics and offers a creative and effective presentation of the role of theology in public life and discourse. I would say that its minor weakness would be an incomplete understanding of economics and an (understandable, given the time of its writing) preoccupation with the polarity between capitalism and communism. The result is that Newbigin's economic critique is a bit off-target. There are legitimate critiques of capitalism to make from his perspective but they require a better appreciation of the virtues of capitalism than he demonstrates. One hopes a latter day disciple will issue a fresh edition with a new foreword that could address this minor shortcoming in an otherwise superb small volume.
In this work, Newbigin explores the relationship of Christianity to power with a searching honesty that few others have matched. While appreciative of Christendom's accomplishments, Newbigin suggests that the power granted the church in Christendom overestimates Christians' grasp of the truth and underestimates the tendency for power to corrupt the church. But the failures of Christendom do not thereby justify completely abandoning the attempt to influence the powers of secular society. Newbigin forcefully argues that Christians cannot simply set aside efforts to influence worldly powers in favor of "sectarian protest" against those powers. Society and it institutions will be guided by some vision of the good life (they cannot be neutral in this regard), and if that vision is the wrong one, much needless harm and spiritual suffering will result. In service to the world, then, Christians must offer their vision of the good life as the truth which should guide individuals and their institutions. Newbigin attempts to articulate an intermediate position (along the lines suggested by Abraham Kuyper) that falls somewhere between Christendom and sectarian protest. Serious questions may be raised about Newbigin's proposal, but his unwillingness to settle for the extremes makes this work a wonderful launching point for further reflection. Whatever model one adopts for Christian activity in the secular sphere, Newbigin suggests that for any engagement with secular culture to be successful Christians will have to first grapple with postmodern pessimism towards the concepts of truth and knowledge. Newbigin considers postmodernity's legitimate insights into the relationship between knowledge and power but moves beyond postmodern skepticism to sketch an epistemology that is appropriately humble yet also hopeful about the possibility of gaining insight into the truth.