To put it simply, McGrath is arguing that Christianity can help us to make sense of the "anthropic principle" (the universe's intriguing friendliness towards life) holistically, comprehending it for its truthfulness, goodness, and beauty. However, McGrath emphasizes the modest scope of this attempt, saying that it is not a proof of the Christian belief in God, but more like a lens to perceive nature as an "authorized sign of the transcendent." (p.12) The book is separated into 2 major parts: A Trinitarian Natural Theology and Fine-Tuning: Observations and Interpretations.
McGrath began by announcing the crisis of natural theology, saying that it has been marginalized by theologians. There are 3 reasons for this crisis. First, the classical natural theology is a product of modernity, out of the Enlightenment. (p.15-16) Hence it doesn't fit in the present era of postmodernity. Secondly, the ambivalence of nature leads "as much to natural atheology as to a natural theology." (p.18, emphasis added) Therefore it is seen as a failure to provide reliable foundation for belief in God. Thirdly, Karl Barth's devastating critique that natural theology is dictated by human rather than God has left a lasting legacy among theologians. (p.18-19) A Trinitarian natural theology is McGrath's remedy for this crisis.
By 'Trinitarian', McGrath meant an understanding of the natural world and our engagement with it as articulated by Christian orthodoxy, "a consequence of Christian revelation." (p.36) This renewed natural theology differs from Deism and Theism in that it "holds that God created the world, continues to direct it through divine providence, and guides the interpreters of both the books of nature and Scripture through the illumination of the Holy Spirit." (p72) It is through this Trinitarian natural theology that we can appreciate the truthfulness, goodness and beauty of the universe's surprising intriguing friendliness to life.
McGrath does not shy from acknowledging that this way of relating Christian revelation to our observation of the natural world is a circular explanation. This circularity set out as "A explains B while B justifies A." By drawing from Carl Hempel's philosophical discussion on science and examples of scientific explanations such as Peter Lipton's theory of cosmology, McGrath argued that, "There is nothing invalid or improper about this form of explanatory argument, which is widely encountered in scientific explanation." (p.52-53)
The rest of the book is McGrath's application of this renewed natural theology to the anthropic principle seen in cosmology, biogenesis, chemistry, and the evolutionary history and complexity of life.
McGrath's project can be summarized as such: The sciences have produced some surprising and puzzling observation about the world, that is it is friendly towards life. And sciences can't tell us why is this so. Natural theology on the other hand, when renewed according to its Trinitarian orientation, can provide the framework to explain sciences' puzzling observation. This is not a proof for God's existence but merely a lens when used provides a clue to the divine. By relating the anthropic principle with the proposed Trinitarian natural theology, McGrath saw "potential to illuminate and enrich both science and religion," and "further the human quest for meaning in this often puzzling and bewildering universe." (p.221)
I have some questions to this volume. First, it has to do with McGrath's anachronistic categorization of natural theology that predates its emergence in the 18th century. If natural theology was recognizably as what it was only from 18th century onwards as "theology that seeks to prove the existence and attributes of God from the evidence of purpose and design in the universe" (p.12), how then could McGrath say there was natural theology recognizably as what it was prior to that?
McGrath categorized Paul's "Areopagus address" and some of the early Church fathers' works as natural theology (p.11), yet if one wants to be categorically precise, these are at best proto-natural-theology and not natural theology.
Unless of course McGrath categorizes these proto-natural-theology as natural theology, which brings me to my second question. One of the main, if not the main, characteristics of natural theology is its contrast from "revelatory" or "revealed theology". For instance,
Natural theology is the practice of philosophically reflecting on the existence and nature of God independent of real or apparent divine revelation of scripture. Traditionally, natural theology involves weighing arguments for and against God's existence, and it is contrasted with revealed theology, which may be carried out within the context of ostensible revelation of scripture. For example, revealed theology may take as authoritative certain New Testament claims about Jesus and then construct a philosophical or theological model for understanding how Jesus may be human and divine. Natural theology, on the other hand, develops arguments about God based on the existence of the cosmos, the very concept of God, and different views of the nature of the cosmos, such as its ostensible order and value.
(Charles Taliaferro, 'The Project of Natural Theology,' in The Blackwell Companion to Natural Theology, eds. William Lane Craig and J. P. Moreland [UK: Wiley-Blackwell, 2009], p.1. Emphasis original.)
McGrath knows about this antithesis between natural theology and revealed theology. Any discussion of the former assumes its contrast from the latter as it is from this antithetical characteristic that each is known to the other. Any coercion of revealed theology into the category of natural theology, or vice versa, one creates a pseudo category. And this seems to be what McGrath has done:
What if natural theology is itself seen as a subordinate aspect of revealed theology, legitimated by the revealed theology rather than by natural presuppositions or insights? What is the authorization of natural theology is understood to lie, not in its own intrinsic structures, nor in an autonomous act of human self-justification, but in divine revelation itself? (p.20)
McGrath envisioned the project as a contribution to the "longstanding debate within the Christian academic community concerning the theological legitimacy and significance of natural theology" (p.xiv), yet ironically in his subordination of natural theology under revealed theology, he has unwittingly confirming and perpetuating its illegitimacy.
So, if classical natural theology is the opposite to revealed theology, and if McGrath's Trinitarian natural theology is "vision of reality articulated by Christian orthodoxy" or "way of looking at things" as "consequence of the Christian revelation" (p.36), then isn't his theology really a revealed theology? If yes, then what McGrath is doing is not so much renewing natural theology but renaming revealed theology.
McGrath distinguishes his Trinitarian approach from the classical natural theology, saying that the latter is
merely one approach to natural theology, in this case shaped by the fundamental assumptions and agendas of the Enlightenment. Yet there are other approaches, such as that adopted and commended in the present volume: the attitude to nature that is mandated and facilitated by the Christian revelation. (p.19)
However, without the characteristic contrast from revealed theology, what is left of natural theology? And this brings me back to the point of McGrath's anachronistic categorization of natural theology: He transposes the renamed revealed theology unto Paul and the early Church fathers so that he can call their proto-natural-theology as natural theology.Besides, is there really other versions of natural theology which predates 18th century other than McGrath's anachronistic category? If not, how then could there be other approaches as claimed? If McGrath insists that his version is really a natural theology---not a renamed revealed theology---then he has not demonstrate what of it that is recognizably as one?
These questions should not overshadow the merit of the book. McGrath's insistence to interpret the natural world through revelation is a call to uphold the centrality of the scripture in Christian's engagement in the sciences. And McGrath has shown how this can be done in the second half of the book.