“Science without religion is lame, but religion without science is blind.” Einstein’s teasing remark is just one of the many contributions by scientists to religious thought that have interested theologians of many shades since antiquity. Recently the debate on science and religion has expanded at a huge rate. Few would now deny that it has an important place in wider discussions about ethics in science or the public’s perception of science.

Historically, religion has motivated both the substance and the interpretation of science. John Polkinghorne is, however, one of the few contributors to this multicoloured debate who can lay claim to professional experience in both science and theology. A theoretical particle physicist until 1981, he retrained in theology and was ordained as an Anglican priest, also serving for a time as president of Queen’s College, Cambridge. He has written a series of influential books – both popular and in a more serious vein – since then, including his Gifford lectures of 1993-4, published as Science and Christian Belief (SPCK 1994).

Physicists with even half an eye on science and religion could fill their bookshelves many times over with the weight of published material. The literature is not only voluminous but also currently rather stratified. The debate presented by the popular media, for example, bears little resemblance to discussions among informed scientists, which is often unrelated to developments in university theology and philosophy departments.

So what – and at what level – is Polkinghorne adding? And what does a physicist-turned-theologian actually have to say about theology? (Polkinghorne’s own answers are that he is one of a small band of “scientist-theologians”, and he is contributing as a “bottom-up thinker”.)

His new book, Faith, Science and Understanding, summarizes his work on science and religion over the last decade and draws together some provisional conclusions. Six of the nine chapters are based on recent lectures and papers, so, inevitably, the collection contains some weak links and repetition. However, some coherence is generated by the division of the book into three broad sections. Polkinghorne first discusses a few “current issues”, then tackles the thorny question of divine agency in the world, before reviewing some other current thinkers in the field.

Polkinghorne’s chosen “issues” set the scene for the book. Closely linked, they cover a defence of theology as a current academic subject and outline his “motivations for belief”. The next two chapters sustain the old tension of theology “revealed” (i.e. by reading sacred books) or “natural” (i.e. by reading from the works of nature). The section concludes by revisiting themes from his earlier books, ranging from critical realism to chaos theory.

So why does Polkinghorne think we should believe in God at all? I find it quite amusing to see just how close his answers are to his reasons why we should believe in, say, quarks or gluons. Polkinghorne’s training as a scientist clearly emerges when he says that the theological project possesses a “defining explanatory principle” and constitutes a “theory of everything”; or when he describes the Bible as “laboratory notebooks of gifted observers of God’s ways with men and women”.

After a while the presentation of every question from this perspective begins to feel claustrophobic – even for a physicist. More alluring is the expressed hope that the wonderful but strange intelligibility of the world might be illuminated by theology. Does our experience of meaning in the way we do science hint at God? I was reminded of the way that the social scientist Peter Berger’s book A Rumour of Angels teases out theological threads from our institutional practice, and rather wished that this, along with other more promising themes, had been developed further.

Another example of Polkinghorne’s light touch is his robust call for renewed belief in the unity of knowledge in academia – with theology as the uniting context. This vital issue has its roots in the early writings of the theologian Tertullian in 3 AD and will unfortunately sound almost ridiculously conservative to the post-modern ear. It is perhaps a shame that Polkinghorne’s overtly conservative Christian theology might predispose more radical readers against his argument here, for surely something is needed to bring a sense of “one world” into our fractured universities.

I am also a little disappointed by the lack of any real discussion of biblical or other sacred texts. There is an unspoken assumption that they are, at best, background material, and at worst irrelevant to the current discussion of science and religion. Yet these texts have been the bedrock of belief for everyone who has worked at the pressure points of science and religion throughout history.

There is, for example, far more relevant material than the hoary old Genesis texts. In fact, I got excited when it looked as if we would be treated in some depth to the most glorious example in the Old Testament – the “Lord’s Answer” to Job ( Job 39-40). It’s a breathtaking poem, working on many levels, posing imaginative and creative questions – surely the central scientific act? – about the workings of the physical world. If you have never read these verses, then I would strongly encourage you to do so. Sadly, they are relegated in Faith, Science and Understanding to an illustration of how we need to choose carefully between images of God offered by the Old Testament.

The theme of the book’s central section has also been Polkinghorne’s central question since he started writing about theology. How, he asks, does God act, or cause things, in the world of space and time? It’s a delicate balancing act: too firm a grip and God gets the blame for everything; too little and the deity becomes dispensable. Of course, science complicates the issue further because it believes that the study of causation (or “ontology”) belongs very firmly to its own patch.

Indeed, our apparently increasing knowledge (“epistemology”) of the physical world seemed in the 18th century to have excluded the idea of a currently active God altogether. Polkinghorne sees, however, in some aspects of 20th-century science – for example, in the “fuzziness” of our knowledge in quantum theory and chaos theory – a way of reconciliation. In a sentence that he likes so much that he serves it up for us twice, he argues that these “epistemological defects become ontological opportunities”. He expresses, as he has in previous books, his preference for the exquisite sensitivity of chaotic dynamic systems in permitting a “top down” flow of causation in nature, calling it “active information”.

There is some nice discussion of how very new scientific ideas engage with very old theological ones. My favourite is the discussion of “kenosis”, or the self-abasing of God in the Christian incarnation. Perhaps a God self-denying enough to become human might also deny himself a total physical mastery of the world. But I would have preferred a more boldly stated case than that which Polkinghorne provides. I also missed any real discussion of the objections to this approach, including the implicit acceptance of a critical realist stance and its limitations. We are told that “almost all scientists” work within a critical realist metaphysics, but where, I wonder, are the statistics? I know several colleagues who are unashamed idealists!

The last section of the book helped me to understand the first two. It’s a helpful summary of the contributions of three other 20th-century thinkers in the field: the mainstream theologian Wolfhart Pannenberg; the reformed theologian Thomas Torrence; and the theoretical physicist and popular-science writer Paul Davies. I am not clear why the choice is so restrictive among the dozen or more names that are given in footnotes to the rest of the text, and many others that are not, but as we have already noted, Polkinghorne tends to steer clear of biblical and historical approaches.

A quirky final chapter has the enticing title “Science and theology in England”. Polkinghorne is clearly proud of England’s “empiricist” inheritance, and of the increasing contribution of his country to the field. However, I was surprised to find no mention at all of the historians John Brooke and Geoff Cantor, paradoxically, in the one section that attempts to draw lessons from history. They have shown elegantly and convincingly how much the study of science and religion benefits from an appreciation of historical context – never more so than at the present. I certainly agree with Polkinghorne’s final judgement that, in this subject, “exciting times lie ahead”.