A motive of credibility is a reason for taking the claims of the Catholic Church seriously. It does not demonstrate their truth by natural reasoning, for we can only properly assent to them by the supernatural virtue of faith, but it does dispose us for receiving the divine gift and, at the very least, presents a challenge to the mind. But where do we find motives of credibility? The First Vatican Council encourages us to look in the Church herself, with her ‘wonderful propagation, outstanding sanctity, and inexhaustible fruitfulness in everything good’. Her capacity for survival and growth against all the odds, the heroism of her saints, and the goods of human culture inspired by her faith: these naturally accessible truths ought, in principle, to convince the non-Catholic that accepting the Catholic faith would not be an unreasonable thing to do.

Fr Aidan Nichols's collected writings on faith and culture constitute a kind of motive of credibility, not only in their subject matter but also in themselves. They are not explicitly proposed as a Catholic apologetic, but that is how I see them and intend to use them. Give these two volumes to an intelligent non-Catholic, or to some dissident son of the Church, and you will probably find he feels provoked, but I doubt if he will feel bored, and I suspect he will be forced to admire the intellectual vitality both of the author and of the Tradition and traditions he represents. The ‘touchstone’ of these essays, Fr Aidan tells us, is ‘epiphany’, which he defines as ‘the illuminating and transforming impact of a plenary Catholicism on a world which already participates, by the creative action of God, in the divine fullness of being and goodness, truth, and beauty’. Notice the word ‘plenary’: for Fr Aidan, the only Catholicism that can illuminate and transform human culture, the only true Catholicism there is, has the note of fullness and wholeness, an integrity of faith and practice undiminished by concessions to that fashion of the world which, with its wisdom, is passing away.

The subject matter of the two volumes of Beyond the Blue Glass – the title comes from Geoffrey Hill, the poet whose Christian themes are discussed in the second volume – is in itself an exuberant display of plenary Catholicism's ‘inexhaustible fruitfulness in all that is good’. Under the rubric of ‘Theology’ in the first volume, Fr Aidan considers the perennial wisdom of his fellow Dominican, St Thomas Aquinas, in relation both to his own century and to the 20th, in the middle of which some of his disciples were moved to resist, as they saw it, the harmful influence of the movement known as the nouvelle théologie. One of the representatives of that movement, Hans Urs von Balthasar, is the subject of two chapters, and in a third, there is an examination of Balthasar's clash with the latter's erstwhile con-frère and collaborator, Karl Rahner. The Trinitarian doctrine of the 19th-century Cologne theologian, Matthias Scheeben, is retrieved from the oblivion to which it has so unjustly and for so long been confined, and another German, Joseph Cardinal Ratzinger, to whose theology Fr Aidan devoted a whole book in the 1980s, appears in his true profile, not as ‘poacher turned gamekeeper’, but as the gardener of theology, who has to prune as well as tend his plants, since the garden of modern Catholicism is ‘vital but rank – in the eloquent Cockney idiom, “blooming awful”’. ‘Liturgy’, a permanent and ever increasing preoccupation of Fr Aidan's, is represented by essays on Odo Casel and Catherine Pickstock, and by a measured comparison of the conciliar Sacrosanctum concilium with the papal Mediator Dei. In the second volume, Fr Aidan takes the demonstration of the fruitfulness of classic Catholicism out of the lecture-hall and sanctuary and into the wider culture, first in a general ‘Sketch for a Christological Aesthetics’, and then in an examination of three artists, a composer and two writers, inspired to some degree or other by the Catholic faith: Olivier Messiaen, Geoffrey Hill and G.K. Chesterton.

Testimony to the Church's tradition of sanctity is given in the second volume with three studies. First, there is an exposition of the spiritual doctrine of the recently beatified, turn-of-the-century Benedictine, Columba Marmion, who by his retreats and spiritual direction guided and encouraged countless priests, religious and laymen in the pursuit of Christian perfection. Secondly, returning home-wards, Fr Aidan discusses the utility of the Rule of St Augustine for the sanctification of friars-preachers. Thirdly, writing more systematically, he sets forth the nature of the Christian priesthood and the priestly call to holiness.

As for what Vatican I calls the Church's ‘wonderful propagation’, that becomes evident in the essays on ‘Ecumenism’. For example, in the chapter on Solovyov, Fr Aidan explores the power of attraction that the papacy, ‘not simply as an icon of the Church's unity but as organizer of her world-transforming action’, was able to exert over a 19th-century Russian Orthodox. In ‘A Catholic Commemoration of Karl Barth’, Fr Aidan shows how the 20th-century's greatest Protestant theologian, who had ‘taken on and seen off’ both the ‘academically entrenched forces of theological liberalism’ and the ‘atheistic and Promethean’ ideology of National Socialism, perceived more clearly than so many Catholics did at the time the ‘menace’ latent in the aggiornamento of the early 1960s, namely, the ‘overtaking of the Church by the world’. Barth's warning, taken up by the young Ratzinger in his book on the last session of the Council and renewed here by Fr Aidan, points to the need for Catholics to recover that non-conformity to the world which, in every age, has been essential to the secret of the Church's ‘wonderful propagation’.

Not only the subjects discussed in Beyond the Blue Glass, but also the qualities of intellect exhibited by the author in discussing them are persuasive motives of credibility for the Catholic religion. If there is a Catholic culture anywhere in this country, it is here, in the prolific work of this Cambridge Dominican. Is there anyone, in either ecclesiastical or secular academies, with anything approaching his scholarly range? Here is a distinguished commentator on Fathers and Doctors and contemporary divines who can also summarize the history of militant Islam in 12 pages, and tell you how much a three-week holiday in Switzerland would have cost a mid-Victorian Englishman. With a generosity of mind that is characteristically Catholic and Thomist, Aidan Nichols is interested in everything, whatever is true, good, and beautiful, as so many participations and likenesses of the First Truth, the Supreme Good, and Uncreated Beauty. Read him, and you'll begin to share something of his own very Dominican gaudium de veritate. Of those writing in English, I can think of no one who is a more exhilarating apologist or, better, preacher, in the cause of ‘plenary Catholicism’.