‘Go to Thomas’, said Pius XI in his encyclical of 1923, Studiorum ducem, written for the sixth centenary of the canonization of Thomas Aquinas. As the patriarch Joseph fed the bodies of his brothers, so, according to the Pope, the friar Thomas nourishes the minds of the faithful with wholesome doctrine. Pius wanted the principles, spirit, and method of the Angelic Doctor to inform Catholic scholarship in all of philosophy and every part of theology, but he gave particular emphasis to the sublimity of St Thomas's ascetical and mystical theology: ‘How extensive the commandment to love God, how charity and the Gifts of the Holy Spirit accompanying it are to increase, the nature and force of the many states of life…: if you wish to have a deep knowledge of these and other such points of ascetical and mystical theology, you should first of all go to the Angelic Doctor.’ At the time Papa Ratti wrote these words, certain theologians, especially Dominicans, were already doing what he proposed. Chief among them was Réginald Garrigou-Lagrange, who in Perfection chrétienne et contemplation selon saint Thomas d'Aquin et saint Jean de la Croix, also published in 1923, argued that the mystical life, in St Thomas's understanding, belongs ‘to the order of sanctifying grace [and] proceeds essentially from “the grace of the virtues and of the Gifts”, and not from graces gratis datae’. Lecturing in England in the same year, our own Vincent McNabb presented the Angelic Doctor ‘as a supreme teacher of that theology which is called mystical’. However, though these pioneers had a sound general understanding of St Thomas's mystical theology, they considered relatively few texts in his works. Like good Thomists in every age, they focused on the rei veritas, in this case what mystical union with God is and how it is to be attained, but, sensitive to the dangers of historicism, they gave little attention to the development of St Thomas's thinking, especially what he learnt from his teacher, St Albert the Great, and, though they recognized that the words St Thomas often quotes from Dionysius, about Hierotheus ‘undergoing divine things’, lie close to the centre of his mysticism, it did not occur to them to investigate in detail their master's reading and appropriation of the Areopagite in those passages that might be called ‘mystical’. These deficiencies have now been met with masterly success by a Dominican of the younger generation, Bernhard Blankenhorn, in what will long remain the definitive work on the mystical theologies of SS. Albert and Thomas and their debt to the one they liked to call ‘Blessed Dionysius’.

Fr Blankenhorn's book is an essay in theology both positive and speculative, or, as people like to say these days, historical and systematic. In both respects, Dionysius the Areopagite takes centre stage. On the historical side, Blankenhorn is interested in the ways in which the reading of his works shaped the thinking of the two friars, the German master and the Italian pupil, about ‘the mystery of union with God’. Albert commented on the entire Dionysian corpus, and made the works of Dionysius and Aristotle the foundational texts of the Cologne studium. Thomas attended Albert's lectures on Dionysius in Cologne; in fact, we have the manuscript of his notes. His own exposition of the Divine Names and what he has to say about Dionysius in other places bear the trace of few commentators other than Albert. Although Thomas first encountered Dionysius's writings in his student days, Blankenhorn concentrates on his later career, since it is there that we find ‘his most extensive remarks on Dionysian union’ (p. 215). In those busy years Thomas reached an understanding of the Areopagite that went beyond the exegesis he learnt from his teacher, indeed beyond his own previous perceptions. Albert refused to identify the Areopagite's language or thought with those of ‘the Platonists’, and the younger Thomas believed Dionysius to be following Aristotle. But in his prooemium to the commentary on The Divine Names Thomas acknowledged that Dionysius used the style and way of speaking of the Platonists, an insight that, according to Blankenhorn, may have been a ‘first in medieval Latin Christendom’ (p. 326). Thomas's doctrine of the naming of God, deeply influenced by Dionysius, is an important part of his understanding of the soul's union with God. We attain union, Thomas says, ‘by ascending through negations’, because by using negations (or ‘remotions’) in naming God we recognize that God is beyond all that we can conceive; negations, as Blankenhorn nicely puts it, ‘shatter our conceptual idols’ (p. 14). However, for Thomas, affirmation has priority over negation; indeed, ‘negation is meaningless without affirmation or positive noetic content, content transmitted by creation, Scripture, and ecclesial mediations’ (p. 435).

In its speculative aspect, Blankenhorn's book shows how, for both St Albert and St Thomas, the theology of man's mystical union with God is rooted in the doctrines of God, One and Triune, of the human being, of the incarnate Word, and of grace. First, Thomas's doctrine of union no less than Albert's has a ‘Trinitarian structure’. It is through the divine missions, the sending of the Son by the Father and of the Holy Spirit by the Father and the Son, sendings both visible and invisible (by grace), that man is drawn into living union with the Holy and Undivided Trinity. Blankenhorn quotes this characteristic text from St Thomas's commentary on the Sentences: ‘Just as the Holy Spirit proceeds invisibly into the mind through the gift of love, so the Son [proceeds] through the gift of wisdom, in which is the Father's manifestation, who is the ultimate to which we return’ (p. 251). Now, since grace is nothing other than the beginning of glory in us, both Albert and Thomas see the created lumen gloriae, too, as a gift of the divine persons sent. ‘The light of glory is a formal cause disposing us for the efficient, exemplary, and final causality of the Son and the Spirit, who lead us to the Father’ (p. 294).

But there can be no union with the Triune Godhead without the humanity of the Son: ‘No one comes to the Father’, says Jesus, ‘except through me’ (Jn. 14: 6). In this regard, Blankenhorn shows the benefit to St Thomas of his ‘unusual access’ in the 1260s to the texts of the Christological councils and the writings of St Cyril of Alexandria. ‘His creative synthesis of these sources with Aristotelian and Neoplatonic metaphysics results in a vision of the Word incarnate as at once the instrumental efficient and exemplary cause of all sanctifying grace for others. We are united to God only through Christ's action in the flesh, and in conformity to his grace’ (p. 268). And if St Thomas's mysticism is Trinitarian and Christological, it is also Pneumatological. His doctrine of the seven gifts of the Holy Spirit, says Blankenhorn, ‘constitutes one of his most original contributions to mystical theology. Indeed, this doctrine has stood at the heart of the Thomistic tradition's teaching on union with God’ (p. 270). According to Blankenhorn, and for that matter Père Garrigou before him, ‘the necessity of the gifts for salvation and their complementarity to the virtues shows that the Spirit's motion is not reserved to a spiritual elite. Rather, it has an indispensable function in the moral progress of all who are in grace’ (p. 280). The seven gifts are always infused with sanctifying grace, and so ‘all who are in grace possess the gift of wisdom (as habitus) and sooner or later enjoy the Spirit's motion to which this gift disposes’ (p. 435).

In their doctrines of man, St Albert and St Thomas ‘critique certain dualistic tendencies in thirteenth-century neo-Augustinian anthropologies and turn to Aristotle as well as to Dionysius for alternative approaches’ (xxi). It is the whole man, body and soul, senses and spirit, who is united by grace with Christ, and through Him with the Father and the Holy Spirit. ‘For Thomas our understanding of revelation or of the graced presence of the indwelling God remains incomplete without reference to what we learn by the senses, thus to perceptions rooted in our experience of the cosmos’ (p. 229). Grace presupposes as well as perfects nature, and so, in that mystical union with the incarnate Word and the Trinity which is the consummation of the life of grace on earth, man's embodied, sensory experience of the world is not discarded: ‘Thomas's doctrine of grace-nature and his exegesis of Genesis move toward a doctrine of mystical cognition that links infused and sense-bound knowledge. For if the grace of Adam and Eve did not suppress the essential function of phantasms for their most illumined noetic acts, then mystical union after the fall likely will not do so, either’ (p. 220).

Fr Blankenhorn's Mystery of Union with God is a magnificent achievement, and for many years to come will be an indispensable secondary source for anyone who seeks to understand the mystical life according to the mind of the Angelic Doctor and his great Swabian teacher.