The doctrine of the Trinity is the summit of Christian revelation, something we should truly be excited about. Yet all too often, the Trinity is something of an embarrassment to Christians – an abstract riddle too difficult to solve. Stratford Caldecott in his book The Radiance of Being does much to redress this negative attitude. His purpose as he states is ‘to think through, as a Catholic layman, the doctrine of the Trinity and its implications for cosmology’. It is hard not to be taken up by Caldecott's enthusiasm. His conviction that the Trinity is ‘the most beautiful, elegant, and simple doctrine in the world – a true theory of everything’ shines throughout his book.

The book is divided into three parts. The first part ‘Nature’ is introduced with a quote from E. I. Watkin about how the old Catholic religion-culture of Europe ‘has been destroyed, overwhelmed by a vast influx of new knowledge, by the scientific mass civilization of the modern world … [but] already in the winter there are signs of the approaching spring.’ Watkin goes on to lay down the challenge that ‘the abiding and immutable truth of metaphysics and revealed religion must be re-clad in the new garments woven by a scientific and historical knowledge incomparably vaster than was ever before possessed by man’ This re-cladding of metaphysics and revealed religion is really what the first part of Caldecott's book is about. So for example, he discusses such topics as Einstein's theory of relativity, quantum electrodynamics, the Big Bang, Cantor's orders of infinity and non-commutative geometry. The pioneer of quantum electrodynamics, Richard Feynman described nature as being absurd and he encouraged people to embrace this absurdity, but for Caldecott, this will not do. Following the Catholic physicist Wolfgang Smith, Caldecott suggests that this shipwreck of modern thought can be attributed to the Cartesian bifurcation between the subjective and the objective. Rather than embracing the absurd consequences of Cartesian philosophy, a viable alternative would be to re-introduce the Aristotelian-Thomistic distinction between actuality and potency into modern physics. It is such thoughts as these that point to the approaching spring that Watkin speaks of. What Caldecott says is certainly not an easy read, but there are enough hooks to latch onto to give one a lot to ponder about.

In the second part of the book, Caldecott discusses the divine nature and he begins by clarifying the meaning of the doctrines of the Incarnation and the Trinity, doctrines which so radically differentiate Christianity from all other religions. But rather than there being any hint of triumphalism, Caldecott sees these central Christian beliefs as treasures that can be more deeply appreciated in the context of inter-religious dialogue. God in his providence has allowed seemingly contradictory religions to flourish and this is a mystery that Caldecott wants to wrestle with. This desire to come to a deeper understanding of the Trinity in the light of other world religions means that his appraisal of them is often very generous. For instance, in his chapter ‘the Mystery of Islam’, Caldecott suggests that Islam is a response to a genuine failing many Christians suffer from, that of polytheism. Just as God used the pagan kings of pre-Christian times to admonish Israel for her many failings, so Islam's strict monotheism admonishes Christians who have strayed into idolatry.

Whilst Caldecott is keen to search for the kernel of truth in every religion, he is careful not to subscribe to perennialism, the belief that there is one kernel of truth from which all religions essentially evolve. As Caldecott points out, perennialism is not easily reconciled with the doctrine of the Trinity, yet he still recognises the value in engaging with perennialism. In particular, he traces how Christians have developed the perennialist idea of the Supreme Identity, that the Absolute and the Self are one, and that the Incarnation of Christ might be understandable as that alone which permits the realisation of the Supreme Identity. Caldecott acknowledges that such speculations are likely to offend both Christians and perennialists, but it does raise the possibility that perennialist philosophy with its strong concept of the Self might be a better vehicle than Greek philosophy for exploring the personhood of the Trinity. Again, it gives one a lot to ponder about.

In the third part of the book, Caldecott takes these Trinitarian reflections, and shows how they can illuminate our understanding of creation's ultimate significance. These reflections come to their climax in the chapter ‘Visions of Sophia?’ Here Caldecott presents some ideas from several mystics and theologians. He ends with considering the systematic theologian Sergius Bulgakov. According to Bulgakov, there is divine Sophia and ‘creaturely’ Sophia. Divine Sophia is the reality to which the word ‘consubstantial’ refers to in the Creed – God's ousia. On the other hand, creaturely Sophia, as Caldecott relates is ‘the foundation on which the entire creation is established, when the Father created all things in the Son and the Spirit brought them to completion. She is at first nothing more than a seed containing the potentiality of the perfect divine image and likeness. But in her all the ideal forms or divine ideas contained in the Son are reflected through creation – that is through a process of temporal becoming, at the end of which they are brought to the fullest possible likeness of divine glory by the Holy Spirit.’

In our modern secular world, such theological speculation is very valuable and important because we deeply need a coherent account of nature which is intrinsically related to God and in which it is intelligible to believe in humanity's divine destiny. To this end, Caldecott, with his breadth of knowledge and deep appreciation of Trinitarian theology is able to show us some very promising signs for the future. To quote Jean-Pierre Torrell OP, ‘Trinitarian theology should not be instrumentalized at the service of other interests, but, without their being in any way subordinated, it illumines all theological reflection worthy of the name’. Caldecott's book surely meets Torrell's criteria for theological reflection – in the light of the Trinity, Caldecott's exploration of being positively radiates.