Newbigin's first three chapters sketch a contrast between modern ways of seeing the world and ways that are normed by respect for Jesus' lordship (we'll call these 'Christian' for simplicity's sake). Though Christian perspectives may or may not be informed by modern perspectives, they bear the essential distinction of contextualizing all things according to the gospel. Newbigin has described the influence (which in the west has often been overwhelming) of modern presuppositions upon both secular and Christian life and thought. That influence is so insidious and so far-reaching that most western Christians do not even realize that they are thinking in ways that are incompatible, or even hostile, to the very faith they profess, and passing those ways along to new generations and new churches in non-western cultures. Yet Newbigin denies that the solution is wholesale rejection of everything modern. What moderns see as an uncrossable chasm between primitive or irrational 'faith' and their own culture's 'reason,' he sees as a bridge from which faith can correct modern perspectives and any other, while healing and incorporating their positive elements.
What I would like you to do is take a stance or a perspective — again, in your church or someone else's, or in your local context (family, neighborhood, home town, dormitory, etc.) — that reflects modern ways of thinking (whether or not that stance is influenced also by your own local culture's ways). I encourage you to take a perspective to which modern ways of thinking have seemed very positive and helpful. (An example from my own family circumstances might be the usefulness of western medicine, say, in the form of orthopedic surgery, for alleviating suffering.)
Now analyze that stance according to both modern convictions and Christian convictions. How does it look on each side of the chasm/bridge Newbigin lays out between Christian perspectives and non-Christian (or inadequately Christian) ones? How might a truly Christan stance on it, on the part of your local Christian community, affect how it lives?
This is an opportunity to 'work with' Newbigin's thesis, but it is also an opportunity to test that thesis to see how strong it is. If you like, treat it skeptically (but fairly) and see how well it passes your test.
You may very well find both our surveys of New Testament writings and Meeks' chapter on early Christian communities helpful as accounts of how the first Christians experienced such shifts in perspective, not toward "the" Christian perspective, but towards local cultural perspectives that were increasingly governed by the faith of the church, and which were constantly dealing with rival perspectives, some of which also understood themselves to be 'Christian' (like the rivals in 1-3 John).
Follow the SAIACS guidelines for writing. I especially like to see proper style, clear writing and reasoning, a thorough answer to the question, and explicit citations of course materials.