This book intends to explain the themes of light and illumination in the theology of St Thomas. As the author points out in his introduction, although these are concepts that frequently recur in Aquinas's work, in many contexts, no synthesis of the passages in which they are found has yet been made (he quotes a recommendation from Chenu that such a synthesis should be attempted). The author aims in particular at two goals (p.3): to provide an overview of St Thomas's systematic theology and to recover the image or notion of light from being ‘a dead metaphor’ (p.80) to one that will deepen our understanding of revelation.

The book roughly follows the order of the Summa Theologiae, in that the author considers Aquinas's references to light in connection with sacra doctrina, theological language, the nature and inner life of God, creation, morality and the incarnation. In addition, one chapter is devoted to St Thomas's understanding of physical light. The author draws our attention (pp. 7–8) to three theses of Aquinas in particular: that illumination is a manifestation of some truth that directs someone to God; that there are three main kinds of illumination, namely of nature, grace and glory; and that the illumination of the mind is a mission of the Son. While quoting principally from the Summa, he also makes generous use of other writings, in particular the Commentary on the gospel of St John.

Thus described, this book may sound like a very valuable enterprise. There are certainly useful things in it. Perhaps the most valuable is the chapter on ‘the Physics of Light’, which explains St Thomas's account of this phenomenon and contrasts it with that of some other mediaevals, such as St Bonaventure. The author explains how St Thomas, on the basis of Aristotle's De Anima and De Sensu et Sensato (mistakenly called De Sensu et Sensate in the list of abbreviations), rejected the idea that light was a body, or something spiritual, or the substantial form of heavenly bodies. He also explains the difference that was sometimes drawn between lux, as a source of light, and lumen as that which is transmitted by the source (although St Thomas can use them as synonyms in the intellectual realm, e.g. 1a q.12 a.5); and the difference between various mediaeval theories of vision. It may be regretted that here as elsewhere he quotes extended passages only in English.

However there appear to this reviewer to be three main faults with the book. The first is that it includes quite a number of inaccurate, or at least imprecise, statements. Among inaccuracies and imprecisions I include the following: the apparent suggestion that before original sin man could know God ‘as He is’ (p.22); that there is no discursive knowledge of God in heaven (pp. 23–24); that God and angels have rational and abstract knowledge (p. 31); that sacra doctrina has some uncertainty ‘from a human perspective’ (p.35); that the object of the agent intellect is all things that can be known (p.36 – as opposed to all corporeal things); that the angelic knowledge of the Trinity does not depend on revelation (this seems to be implied on p 37); that some scriptural authors did not write under inspiration (p. 42 – he surely means, by revelation); that all truths are known in the beatific vision (p.104); that Aquinas proves that God is infinite truth by considering the infinite multitude of created truths (ibid.); that illumination is proper (rather than ‘appropriated’) to the Son (p.112); that the three spiritual lights correspond to the three forms of Christ's human knowledge distinguished by St Thomas (115-16); that Aquinas calls the light of glory, rather than God Himself, the ‘intelligible form of the intellect’ (p.131); that it is more a theological than a metaphysical necessity that the soul be immaterial (p.158); that there is a ‘continuum’ between divine, angelic and human knowledge (p.149); that angels' knowledge is not of particulars (p.164-65); that the fall took from man all knowledge of God (p.165); that the ‘intelligible principle’ that man ignores in sinning is God (p.178); that the first principle of practical reason is ‘the good is what all seek’ (p.187); that the pagans did not possess ‘synderesis’ (p.190, contrary to 1a q. 79 a.12); that the cardinal virtues are ‘normally’ acquired although they ‘may be’ infused (p.194); that Christ's descent into hell was a spiritual journey (p.206). Although it is sometimes rather the author's language than his meaning that could be criticised, this catalogue shows that the book is not entirely reliable as a guide to Aquinas's thought.

The second problem is that it often seems that not much is in fact gained by describing the various parts of St Thomas's theology with reference to light. For example, although, as the author notes, Aquinas uses the instantaneous illumination of the air by the sun as a ‘model’ to explain both God's preservation of all things in being, and His infusion of the virtues into the soul, it does not seem that one can describe these and similar passages as constituting a ‘theology of light’. Often it seems that the author has simply sought out the various places in Aquinas's work where the term ‘light’ appears, and commented on them; which gives the book a material and not a formal unity.

A third problem is that the notion of spiritual light is itself not sufficiently examined. At one point (p.102) the author says that it is a metaphor for Aquinas, at another that it is not (p.86). Although he makes use of the Commentary on the Divine Names, the key article in the Summa (1a q.67 a.1) is left in the background. All this leaves the status of the text ‘God is light’ uncertain. He states that this divine attribute is appropriated to the Son, and implies that this is St Thomas's teaching, but does not prove this from the texts, not consider the statement of the Nicene Creed that the Son is ‘light from light’. With regard to created spiritual light, one might have hoped for a fuller discussion of the relation between faith and prophecy, and in what sense these lights are compatible with obscurity. He could also have considered whether a distinction between lux and lumen exists in the intelligible realm.

For all these reasons this book appears as a first sketch rather than a finished presentation of the notion of light and illumination according to St Thomas.