Rorate Caeli

The Eucharist: What is said and done around this sacrament and during its celebration

A book review 
by Clemens Victor Oldendorf of Urban Hannon's Thomistic Mystagogy: St. Thomas Aquinas's Commentaries on the MassTranslated from German by Peter Kwasniewski.

Born in 1225, St. Thomas Aquinas died 750 years ago this past March 7. Those who observe the liturgical calendar that corresponds to the traditional Roman rite celebrate the feast of Aquinas on this date every year and therefore celebrated it just over a month ago.

On the occasion of such a remarkable historical commemoration, it is fitting to once again take a conscientious look at the life and teachings of the Doctor Communis, and this examination can be quite intense, because throughout the next year we will be commemorating the 800th anniversary of the birth of this authoritative theologian prince from the Dominican order. In 2024 and 2025, we will once again have a seamlessly merging double jubilee for St. Thomas Aquinas and all those who venerate him and draw on his philosophical and theological achievements.

Timely new publication

As if in honor of these occasions, a work has been published by the American publishing house of Os Justi Press on March 7, 2024, as the 11th volume of the academic series Os Justi Studies in Catholic Tradition, which aims to present Thomas Aquinas from an initially unusual perspective, namely as a mystagogue of the Holy Mass in its traditional form, in which he essentially found it and in which it has hardly changed to this day for Catholics faithful to tradition.

The contribution to be presented here is an excellent addition to these studies on Catholic tradition. The author is Urban Hannon, a young theologian who was born in the USA and has already obtained a degree in theology at the Dominican College of Rome, the Angelicum. He is now a seminarian of the Priestly Fraternity of St. Peter in Wigratzbad.

Theologian, hymnologist and mystagogue at the celebration of the Eucharist

On closer consideration, Thomas as a mystagogue is perhaps not so surprising when you consider how influential and powerful he was as a philosopher and theologian in the intellectual illumination and terminological formulation of transubstantiation and the Eucharistic Real Presence. If we want to read and understand him mystagogically, we move to a certain extent with him in the intermediate field that opens up between his seemingly sober and dry efforts as a representative of scholasticism about the sacrament of the altar on the one hand and his hymnic poetry about the Eucharist on the other, since he had, as is well known, compiled and poetically created the liturgical Office and Mass form of the new feast on behalf of the Pope when the feast of Corpus Christi was introduced.

Nevertheless, Hannon rightly states in his introduction:

Unlike his teacher St. Albert the Great[1] and many of their contemporaries, St. Thomas never wrote a stand-alone commentary on the eucharistie liturgy. Nevertheless, and unbeknownst to many, St. Thomas did write his own expositio Missae. In fact, he wrote two: one in his earliest major work, the other in his latest. The former is hidden away in the expositio textus of Book 4, Distinction 8, in his Scriptum on the Sentences of Peter Lombard. The latter is in the corpus of Summa Theologiae, Tertia Pars, Question 83, Article 4. Both of these treatments include a division of the liturgy into its essential parts, as well as a detailed study of the words that comprise each part—that is, "the things said around this sacrament," the many words of the whole Mass that surround the few words of institution. For although only that barest form is necessary for the mere being of the sacrament, all the words of the rite are necessary for its well-being.[2]

In addition, there are all the actions and gestures, which must accompany the words spoken during the entire Mass rite.[3]

The source texts on which Hannon mainly relies are In IV Sent., d. 8, ex. and In IV Sent., d. 12, ex. as well as ST IIIa, Q. 83, specifically articles 4 and 5. These texts can all be found in Latin and English in Appendix 1.[4] The Latin version can also be found on the Internet at, while the translation is always by Urban Hannon and was produced especially for this publication.[5] This is highly commendable, as the author’s own translation decisions often clarify his understanding and interpretation of the text. It can be said in advance that the English translation is of very high quality and meets with no major reservations or objections.[6]

High-caliber foreword places the work in a genesis and context

“lt is no exaggeration to say that Fr. Hugh Barbour, O. Praem., has taught me more about the holy Mass than anyone else l've ever known,” the author states in his prefatory acknowledgments[7] and it is truly a great stroke of luck that he was able to win over the learned Premonstratensian of Saint Michael’s Abbey in the Californian Silverado for an unusually substantial foreword.[8] Only two or actually three points of view that are addressed in it are mentioned here to give an idea of the extraordinary value of this foreword.

Firstly, Barbour reminds us of Dom Ansgar Vonier (1875-1938), the second abbot of the English Benedictine abbey Buckfast Abbey, which was revived in 1882, and his book A Key to the Doctrine of the Eucharist. About a century after Vonier’s book, Barbour attests that Hannon has congenially completed the Benedictine abbot’s work with Thomistic Mystagogy.[9]

No sacramental or rubrical distillation of the liturgical rite

Another important point that Hugh Barbour makes in Hannon’s book is that an authentic reading of Thomas does not lead to a positivism in which the validity of the rite - always using the example of the sacrament of the altar - is exhausted in isolated words of the Lord or in which one is satisfied with a liturgically correct but mechanized rite. “And yet it is just this sort of positivism which characterizes the preoccupation of the intervening liturgical movements, pre- and post-conciliar, and their approaches to the Mass.”[10]

One last aspect, which we would like to mention here from the preface and which is illustrated there by means of a vivid example, is important because it insists that Thomas should not be approached with a modern understanding of genius, which all too often equates or confuses it with originality:

Too often, in their zeal to justify the Angelic Doctor's superiority, Thomists have looked for some new insight or essentially "Thomistic" teaching, hitherto unknown. Here, however, in Thomas's mystagogical instructions, as in all his teaching on sacramental and liturgical matters, we find only a faithful recitation of what has been handed on in the rite of the sacraments, and which might easily have been written by almost any twelfth- or thirteenth-century theologian.[11]

The genius of tradition instead of the originality of Thomas Aquinas

The Premonstratensian canon demonstrates this by writing: “Nowhere is this attitude more evident in Thomas than in his preferential and almost exclusive preference for Pseudo-Dyonisius Areopagita, whom he prefers to call simply Dionysius, in all matters of hierarchical worship, be it the sacramental or that of the angels. This basic attitude is an all-pervading one.”[12]

This preference of Thomas for the pseudo-Areopagite is further explained in the corresponding footnote of the preface:

In fact, throughout the works of St. Thomas, Dionysius is regarded as a supreme authority after sacred scripture and before the other Fathers in exegesis, theological method, metaphysics, and angelology, as well as in liturgy and spirituality. This, it is said, is because he is presumed to be the earliest non-canonical writer, the convert of St. Paul at Athens named in Acts 17. And yet it can hardly be that an authority so developed, consistent, and universal could be based only on a simple historical error. The content of his teaching, however historically recommended, is beyond question. The Areopagite's teaching and the Church's reception of it are undeniable and immoveable facts of history and Christian theology. One need only examine, for example, the acute use of the Areopagite in medieval English vernacular literature on prayer to verify its far-reaching influence. Of no one else did St. Thomas say in the most absolute terms, and precisely regarding the metaphysical principles of speculative thought, what he said of the Areopagite and his Christian Platonist disciples in his commentary De Divinis Nominibus: "Verissima est eorum opinio[their opinion is the truest].[13]

In the concluding sentences of this footnote, Dom Hugh Barbour OPraem expresses the hope that those who are engaged in theological research on Thomas would like to draw the consequence from his unique appreciation of the Areopagite and receive the impulse to initiate and purposefully begin a movement of decidedly Dionysian interpretation of Thomas.[14]

objectives pursued and achieved with Thomistic Mystagogy

With his writing, our author would like to try to put together the parts of a coherent, “independent Thomistic commentary on the Mass” from the four major source texts already mentioned[15] and to be “sensitive to the nuances.”[16] It is striking how much continuity is maintained between the texts from the commentary on the Sentences (written in Paris between 1252 and 1254) and those from the Summa Theologiae (on which Thomas worked in the various locations of Rome, Paris and Naples in the period from 1268 to 1273), even though around two decades had passed between them.[17]

Thomas does not later repeat some of the distinctions made in the Commentary on the Sentences[18] but in the Summa Theologiae he introduces the seemingly essential distinction between sacrifice (sacrificium) and sacrament (sacramentum).[19]

Procedure in Thomistic Mystagogy

In the first chapter, entitled Divisio Missae, Hannon uses the example of the structure of the liturgy of the Mass to explain St. Thomas’ method, his approach when he deals with a text in a very broad sense. Then it is not only a matter of grasping its content, but also and perhaps even more so of understanding how text and content are ordered and, from the knowledge of this order, to work out an outline for oneself that maps the structure of the text under discussion and its message, so to speak, and makes it comprehensible.[20]

In the commentary on the Sentences, Thomas starts from the principle of exitus-reditus, which he adopts from Dyonisius Areopagita.[21] With reference to the oration Actiones nostras, which is probably familiar to some readers from the Litany of All Saints, Hannon could have explained this principle very clearly and easily understood: “We pray, Lord, come before our actions with your inspiration and accompany them with your help, so that all our prayers and actions may always begin with you and, as begun by you, may be completed by you.”[22]

Organization according to liturgical services or roles: the liturgical performance

Thomas gains a further organizational structure, as it were, by analyzing the liturgical distribution of roles between priest, assistants (deacon and subdeacon), and the so-called choir, which in a monastic context would be understood as the monastic community present, otherwise ideally the schola—in each case extended by the faithful present.[23] Finally, he follows the tradition of allegorical explanation of the Mass or interpretation of Scripture and recognizes in the liturgy correspondences between prefiguration and fulfilment as well as a sensus spiritualis.[24]

When we spoke earlier of the preoccupation with a text, it is crucial to understand Hannon’s pointing out that Thomas, when he deals with the liturgy of the Mass, starts less from a book, i.e. from a missal, than from the liturgical celebration and celebration itself, for the performance of which a particular liturgical book is used.[25]

Genuinely Thomistic mystagogy of the Holy Mass is unfolded

The second chapter, by far the most detailed[26] then focuses on the Expositio Missae. Hannon presents here, as was his intention, a linear explanation of the Mass, his actual Thomistic mystagogy. Overall, he succeeds very conclusively in harmonizing the approaches found in the two main sources from the Commentary on the Sentences and the Summa Theologiae and, in particular, does not make the mistake of understanding the clarifications made in the latter text as corrections that would simply revoke and retract the positions taken in the earlier one. There are shifts in emphasis, and these are also identified, but all stages of development ultimately contribute to the mystagogy of St. Thomas Aquinas that finally emerges and which Urban Hannon presents to us in his study.

Passage and interpretation of the liturgy of the Mass with Thomas Aquinas

The description of the liturgical process, its interpretation and meaning, which the author draws from the sources he consulted, begins with the confession of guilt in the Confiteor.[27] in the Confiteor, but the actual beginning is the Introit together with the Collect, which is followed at the end by the double structure of the communion verse and closing prayer, where a concluding blessing is not mentioned.[28] From the continuous presentation of the entire liturgy of the Mass, as the author allows it to unfold in between, we will only pick out striking passages that may be particularly noticeable or even astonishing due to Thomas’ interpretation; furthermore, those where Hannon’s translation from the Latin is not convincing and sometimes suggests a probable misunderstanding of the text passages in question on his part.

Queries and suggestions

Thomas makes a distinction between the terms oblatio and consecratio and the way in which he assigns the terms sacrificium and sacramentum to them. There we read: “Quod quidem et offertur ut sacrificium, et consecratur et sumitur ut sacramentum, primo enim peragitur oblatio; secundo consecratio materiae oblatae; tertio, perceptio eiusdem.”[29] As a result, the concept of consecration is surprisingly not brought together with that of sacrificium, but with that of the sacrament, insofar as the Eucharist is enjoyed and received as food (and drink). The relationship exists between sacrificium and oblatio, whereby this offering seems to be determined by the logic of referring primarily to bread and wine[30] which can then be brought into agreement with the later doctrine of Trent, if one assumes two priestly potestates offerendi et consecrandi which certainly work together, but are conceptually and factually distinct from one another.[31]

In the intellectual context, it should be noted what Hannon has already stated earlier, namely that St. Thomas “has very little to say about the offertory itself, only that it is expressed by the priest’s prayer Suscipe sancta Trinitas.” This corresponds to the Dominican rite, in which the chalice and host are raised together during the preparation of the gifts, with the host resting on the paten, which lies on the chalice with wine and a little water mixed in.

When all the texts Hannon refers to were written, the standardization of liturgical customs in the Dominican Order had already been completed, as this codification had taken place in 1246 and were reaffirmed in their binding nature in the two following years. At this point, we can see that Thomas understandably had the liturgy of his order in mind, but he seems to have deliberately refrained from mentioning the differences between the various liturgical observances in order to be as universal as possible. In this respect, as a reviewer I would intuitively answer the question that Hannon raises towards the end of his study, namely which missal St. Thomas may have had in mind when compiling his texts.[32]

Liturgical tradition as consuetudo

How one understands the following sentence from ST IIIa, Q. 83, a. 5 sc, depends on how one authoritatively determines the relationship between liturgical tradition and ecclesiastical authority in matters of worship. This passage reads in Latin: “Sed in contrarium est Ecclesiae consuetudo, quae errare non potest, utpote spiritu sancto instructa.”[33]

Certainly prompted by the majuscule in the word Ecclesiae, which, however, is unmistakably in the genitive singular, Hannon apparently sees here a personification of the Church, treating it as if it were the actual subject of the sentence and translates: “But in the contrary is the custom of the Church, who cannot err, as she is instructed by the Holy Spirit.”[34] However, supported by grammar and word order in Latin and by the entire context of Thomas Aquinas’ argument, he is saying: “But in contrast to this stands the Consuetudo Ecclesiae, which cannot err, for it [= the Consuetudo Ecclesiae, CVO] is instructed by the Holy Spirit.” Hannon might at least consider whether it would not be more appropriate to formulate the line: “But in the contrary is the Consuetudo of the Church, which [italics for emphasis] cannot err, as it [= the custom of the Church] is instructed by the Holy Spirit”.

Thomas’ mystagogy in contrast to all the liturgical reforms of the 20th century

In my opinion, this would make it clearer that the authority of the Church to order its worship is not independent of its consuetudo and cannot legitimately consist in replacing a long-practiced consuetudo with a fundamentally new consuetudo against this inherited practice. If the authority of the Church does not rest on the principle of tradition in its liturgy, then the danger of aliter celebrare (celebrating in a manner different from what ought to be done), which Hannon also rightly warns against, could suddenly find ample room[35]. It would run completely counter to his overall style if one were to assume that the author of Thomistic Mystagogy wanted to endorse such a reformist view (i.e., whatever the Church puts forward must be right) — a view that unfortunately comes to the fore in Traditionis Custodes.

Last year, the anthology Liturgical Theology in Thomas Aquinas: Sacrifice and Salvation History was published in Washington DC from the estate of the important Thomist and liturgist Abbé Franck Quoëx (1967-2007), a priest who in the end belonged to the clergy of the Archdiocese of Vaduz. Urban Hannon’s Thomistic Mystagogy now belongs in the same line. The relative brevity of his publication should not lead us to underestimate its content. Its concise brevity offers the interested theological layman the advantage of easier readability and thus even quicker access to essential insights.

Thomistic Mystagogy is available from the publisher (here) and from all Amazon outlets.


[1] Cf. Albertus Magnus, De Mysterio Missae, in: Auguste and Êmile Borgnet (eds.), B. Alberti Magni, Ratisbonensis Episcopi, Ordinis Praedicatorum, Opera Omnia, vol. 38, Paris 1899, pp. 1-189. Unfortunately, this treatise is not yet available in the critical Editio Coloniensis of Albert the Great’s works. Cf. also: Albertus Magnus, On the Eucharist. Commentary on the Holy Mass “De mysterio missae” and selected passages from “De corpore Domini” [= Christliche Meister 64], Einsiedeln2 2018. Albertus Magnus, nicknamed Doctor Universalis, was around 25 years older than his pupil Thomas and outlived him by six years.

[2] Hannon, Thomistic Mystagogy , p. 5f, unless otherwise indicated, italics according to the original English text.

[3] Cf. ibid., p. 7.

[4] Cf. ibid., pp. 99-169.

[5] Cf. ibid. p. xx.

[6] I expressed some criticisms in the German version of this review, but Os Justi Press subsequently corrected the mistakes that I had pointed out, and the new files are already uploaded.

[7] Cf. ibid., Acknowledgements, pp. xix-xxi, here: p. xxi.

[8] Cf. ibid., Foreword, pp. xi-xvii.

[9] Cf. ibid. p. xiii. 

[10] Ibid, p. xiv.

[11] Ibid, p. xvi.

[12] Ibid, loc. cit.

[13] Ibid., p. xvif., fn. 2. Incidentally, the footnote count in this book starts at the beginning of each chapter, which is not a disadvantage in terms of clarity.

[14] Cf. ibid., p. xvii, fn. 2.

[15] Cf. ibid. p. 7.

[16] Cf. ibid. loc. cit.

[17] Cf. ibid. p. 13.

[18] Cf. ibid. p. 14.

[19] Cf. ibid. loc. cit.

[20] Cf. Hannon, Thomistic Mystagogy, pp. 9f.

[21] Cf. ibid. p. 10.

[22] Ramm, M., Volksmissale. Das vollständige Römische Messbuch nach der Ordnung von 1962, Thalwil4 2022, p. 514 T, right column, whereby the translation there after the word “auch” by repeating the word sequence “through You” is added, which is closer to the Latin original and makes it clearer how everything starts from God and returns or should return to Him. This is precisely the principle of an ideal cycle applied by Thomas and adopted by the Areopagite.

[23] Cf. Hannon, Thomistic Mystagogy, pp. 14-21.

[24] Cf. ibid. p. 21f.

[25] Cf. ibid. p. 10.

[26] Cf. ibid., pp. 23-91.

[27] Cf. ibid. p. 23.

[28] Cf. ibid, p. 89 in conjunction with footnote 241 the quotation from the commentary on the Sentences.

[29] Ibid. p. 134, italics for emphasis.

[30] Cf. later the Council of Trent, DH 1751.

[31] Cf. DH 1771.

[32] Cf. Hannon, Thomistic Mystagogy, p. 95. The author lists a total of seven such research questions ibid., pp. 94-96 in order to stimulate further investigation. Perhaps he will take up some of them himself in the future and personally find a solution to them.

[33] Ibid, p. 152.

[34] Ibid, p. 94 in conjunction with footnote 3 and p. 153.

[35] Cf. ibid., p. 93 in conjunction with footnote 1.