On November 20, 1947, Pope Pius XII promulgated the encyclical Mediator Dei. This letter marked a watershed moment in the modern history of the Church. The first papal encyclical devoted specifically and entirely to the liturgy, its significance can be seen not only in itself, but in what it began; for Mediator Dei constitutes the foundation and starting point of the movement towards liturgical reform that culminated in the Second Vatican Council. Pope Pius did far more than simply legislate for or regulate the liturgy: he provided a thorough and systematic theological treatment of the Church’s worship, one which bore abundant fruit in the ensuing decades, and the document’s ramifications have yet to be fully realized.
Mediator Dei (MD), as Pope Emeritus Benedict XVI said in 2008, “gave an impetus to the liturgical movement,” and distilled “the best insights” of it for the universal Church. At the time of its publication, the foremost American liturgical journal, Orate Fratres, said that by it the Holy Father had “granted official Catholic status” to the liturgical movement. Furthermore, no less a personage than Dom Lambert Beauduin (1873-1960), among the earliest pioneers of the Liturgical Movement, wrote that by this letter Pope Pius had elucidated “the basic prerogatives which entitle the liturgy to a post of the first order in the spiritual life.” Because of it, J.E. Kelly wrote in the proceedings of the 1948 liturgical week, “The Liturgical endeavor” became “an apostolate incumbent upon all.” Pope Pius XII provides a definition of liturgy and a description of liturgical development, which have led some liturgical scholars to describe the encyclical as the Magna Carta of the Liturgical Movement.
Sign of Maturity
Mediator Dei is a sign that the Liturgical Movement had, in a sense, reached maturity. Pope Pius XII recognized this development, praised the advancements in scholarship and understanding that the movement had contributed, and sought to consolidate those gains. He intended to encourage further effort, as well as to “take proper steps to preserve it…from excess or outright perversion” (MD, 7). He observed that, unfortunately, there were still “places where the spirit, understanding or practice of the sacred liturgy is defective” (MD, 8). Thus, Pope Pius XII set out to “restrain the overbold,” as well as to “correct the faults of those who are negligent and sluggish” (MD, 9).
The Liturgical Movement had experienced a noticeable intensification of activity in the years following World War I. In part this was due to the freeing of academic and cultural energies that had been stifled by the war. But there was also a growing awareness that the crisis of civilization represented by the war called for a revival of faith, and therefore a revivification of the Church’s worship. There was a sense that the West was adrift and in danger of becoming wholly lost. The ravages of the Second World War and the ensuing descent of much of the world beneath the shadow of communism showed that, if anything, the situation had become even more dire. And so, Pope Pius XII wrote, “after a long and cruel war which has rent whole peoples asunder with its rivalry and slaughter,” “the needs of our day and age demand” an effort to “restore peace” and to become “one brotherhood.” The Holy Father believed that “no plan or initiative can offer a better prospect of success than that fervent religious spirit and zeal by which Christians must be formed and guided” (MD, 12). Far from being an otherworldly concern, the Holy Father and others saw the cultivation of what Pius X (1903-1914) had called “the liturgical spirit” as the primary antidote to the afflictions of the present age. Following his predecessor, Pius XII saw that by “active participation” in the liturgy, the divine life “flowing from the head is imparted to the members” for the work of the sanctification of the world (MD, 78).
Priestly Order in Action
The encyclical may be divided into four parts, along with an introduction and a conclusion. The first part is a treatment of the nature and development of the liturgy. This section and the one succeeding it are the most systematically theological. In the first section Pius XII describes the liturgy as the public worship of the Church and describes the liturgy as the consequence of the incarnation of the Lord, and the means by which the Lord continues and extends his presence to the Church in the world. The Pope sets forth the origins of the liturgy in the Old Testament and its recapitulation as the means of conferring and strengthening the life of the new covenant. Furthermore, Pius XII reiterates and expands previous magisterial teaching on the primacy of the interior element of divine worship.
After a discussion of “piety,” “devotion,” and the capacity or sufficiency of the sacraments in themselves to convey and dispense divine grace, he underscores the unity and complementarity of the liturgical act, the sanctification of its participants, and the consequent action of the members of the body in the world. This appraisal leads to a discussion of the ecclesial nature of the liturgy and the role of the hierarchy and teaching office of the Church in the celebration and regulation of liturgical life. Pope Pius, in concluding this section, provides an important discussion of the nature of liturgical development and the means of discerning and regulating that process. Rather than something fixed or static, the Holy Father saw the liturgy as “capable of evolution.” The liturgy grows and changes in its human components, “as the needs of the age, circumstance and the good of souls may require,” under the care and guidance of the hierarchy (MD, 50).
Nature of Worship
The second section of the encyclical is a treatment of the nature of the Eucharist and our worship in the Mass. It begins with a summary of the Church’s teaching on the Eucharist: the renewal of Christ’s bloody sacrifice perpetuated in an unbloody way, the unicity of the sacrifice of Calvary, that of the Last Supper, and its re-presentation in the Eucharistic liturgy. Pope Pius also provides a précis of the four ends of the Mass (MD, 71-74):
1. The glorification of God: Christ’s self-immolation in obedience to the Father is the supreme act of glorifying God.
2. Our thanksgiving to God: Christ alone was capable of making a worthy return to God, and this thanksgiving is perpetuated in the sacrifice of the altar.
3. Expiation, propitiation, and reconciliation: Christ was uniquely fitted to make satisfaction to God for the sins of mankind. That propitiation is renewed daily at the altar.
4. Impetration: the word “impetration” comes from the Latin verb impetrare, meaning to seek or obtain by request or entreaty. It is ensured petition, so that “we may be filled with every blessing and grace.”
After this description of the ends of the Mass, the encyclical continues with a discussion of the necessity and the means by which we are individually brought into “vital contact with the sacrifice of the cross, so that its merits…should be imparted to [us]” (MD, 77). Christ wished that “all should approach and be drawn to his cross…to obtain the salutary fruits produced by him upon it.” But it was not enough that we should receive those fruits in a purely passive way. Continuing the teaching of Pope Pius X in Tra le sollecitudini (1903), Pius XII explains that we receive the sanctification made present through the liturgy by means of our “active and individual participation” (MD, 78).
That participation, the encyclical continues, is the “chief duty and supreme dignity” of the faithful (MD, 80). While cautioning that the faithful do not offer the sacrifice in the same way as the ordained priest, who is configured to Christ the head, nonetheless, the faithful do “offer” the sacrifice in cooperation with the priest. The Holy Father adduces the “Orate, fratres” as evidence of this: “Pray brethren that my sacrifice and yours may be acceptable to God, the Father Almighty” (MD, 87; Roman Missal). Furthermore, he explains, the people are united with both the ordained priest and our one High Priest “in praise, impetration, expiation and thanksgiving” (MD, 93), as a consequence of our baptismal incorporation into the body of Christ, and thereby, our participation in his priesthood (MD, 88).
This discussion concludes with an explanation of the importance of Holy Communion and the fittingness and merits of Eucharistic adoration. In his letter, Pope Pius XII reiterates the teaching of Trent that the communion of the faithful is not necessary for the validity of Mass, but he also exhorts Catholics to receive Holy Communion frequently and devoutly, so that we may be united to the Lord “in the spirit of the most ardent charity” (MD, 115-117). United to the Lord by the reception of Holy Communion, in adoration the faithful “bear witness to solemnly avow the faith of the Church that the Word of God is identical with the Son of the Virgin Mary, who suffered on the cross, who is present in a hidden manner in the Eucharist and who reigns upon his heavenly throne” (MD, 134).
Hours and Years
The third section of the encyclical is devoted to the Divine Office and the Liturgical Year. By means of the Divine Office, or the Liturgy of the Hours, the Church’s worship of God, which has its source and origin in the Eucharist, is “directed and arranged in such a way that it embraces…the hours of the day” (MD, 138). With the Divine Office the Church fulfills the Lord’s command “to pray always,” with the result that mind and heart ascend to God in union with Christ (MD, 145).
The Holy Father recognizes that, in our own time, the practice of the regular singing or recitation of the Divine Office is largely maintained in monasteries or religious communities. But he exhorts bishops and pastors to continue or to revive the practice of reciting or singing Vespers in parish churches. By this means, he asserts, Sundays will be kept holy and the people will be more closely united to the prayer of the whole Church (MD, 150).
After a brief outline of the liturgical year, Pope Pius explains that the cycle of divine mysteries observed in time is a consequence of the Incarnation. He writes, “In the sacred liturgy, the whole Christ is proposed to us in all the circumstances of His life, as the Word of the eternal Father, as born of the Virgin Mother of God, as He who teaches us truth, heals the sick, consoles the afflicted, who endures suffering and who dies; finally, as He who rose triumphantly from the dead and who, reigning in the glory of heaven, sends us the Holy Paraclete and who abides in His Church forever; ‘“Jesus Christ, yesterday and today, and the same forever’” (MD, 163).
This phrase, “the whole Christ,” is reminiscent of the language Dom Odo Casel (1886-1948) uses in his seminal work The Mystery of Christian Worship. In Casel’s thought, which Pope Emeritus Benedict described as “the most fruitful theological idea of the 20th century,” through the liturgy we encounter and participate in the “whole Christ,” and in the liturgical year we, who are limited by quotidian time, are nonetheless made present to the entirety of Christ’s life and saving work. Thus, Pope Pius explains, the liturgical year “is not a cold and lifeless representation of the events of the past, or a simple and bare record of a former age. It is Christ himself who is ever living in his Church…. [T]hese mysteries are ever present and active…, not in a vague and uncertain way…, [but] they still influence us because each mystery brings its own special grace for our salvation” (MD, 165).
Finally, this section concludes with a brief discussion of the sanctoral cycle, and the means by which the feasts of the saints provide constant guidance, examples, and, most importantly, occasions for the saints’ fellowship and intercession.
The final section of the encyclical deals with practical pastoral instructions. In it Pope Pius encourages the multiplicity of legitimate devotions and reiterates his teaching that there can be no “real opposition between the sacred liturgy and other religious practices, provided they be kept within legitimate bounds and performed for a legitimate purpose” (MD, 173). Legitimate devotions, he says, “develop a deeper spiritual life of the faithful” and “prepare them to take part in sacred public functions with greater fruit.” Thus devotions, in their proper place, are complementary or preparatory for full participation in the liturgy. He sets forth, however, the norm that the liturgy should exercise “a salutary influence” on devotions so that “nothing improper be introduced.” In other words, the liturgy is both prior to and of a higher order than devotions. The devotional life of the faithful should flow from the liturgy, not vice versa (MD, 184).
Pope Pius XII, like his predecessors, encourages the use of Gregorian chant, and confirms its status as the normative music of the Roman Rite liturgy. He continues Pius X’s and Pius XI’s call for the restoration of Gregorian chant to the people and exhorts pastors to promote congregational singing as a testimony to the unity of the hearts and minds of the faithful (MD, 191-194).
After remarks concerning the education of seminarians and the selection and training of altar servers, the Holy Father commands pastors to be vigilant against errors and zealous for the liturgical formation of their people. The encyclical concludes with a prayer that God would “graciously grant to us all that during our earthly exile we may with one mind and one heart participate in the sacred liturgy which is…a preparation and token of that heavenly liturgy in which we hope one day to sing together with the most glorious Mother of God…. To him that sitteth on the throne and to the Lamb, benediction and honor, and glory and power forever and ever” (MD 209).
Pius XII sought, as he wrote, to restrain the excesses of some liturgists, and to spur the half-hearted and lukewarm to greater effort. The excesses he sought to restrain were, firstly, what Father Aidan Nichols described as “hyper-liturgism:” an extreme prioritizing of the liturgy in its “objectivity” over devotions, which were disparaged as merely “subjective.” Pope Pius corrects this error by insisting that subjective devotion is not only helpful, but necessary if the liturgy is to have a full effect in the worshipers’ lives. As Nichols explains, this aspect of Mediator Dei was intended to preclude the possibility of any rift developing between the liturgical life of the faithful and the “mystical tradition of personal prayer in the Church.” One cannot promote the authentic liturgical life of the Church by disparaging the legitimate devotions of the faithful.
Another object of the encyclical is to assert and clarify the authority of the Holy See in liturgical matters. As Alcuin Reid explains, “This is a strong refrain running throughout the encyclical” and is a result of the Holy Father’s concern to restrain liturgical excesses. In paragraph 9, Pope Pius asserts his “prerogative to command and approve whatever is done properly, and to check or censure any aberration” (MD, 9), and paragraphs 60-65 contain repeated references to the Holy See regulating the use of the vernacular, liturgical music, and the possession of the overall responsibility to govern the Christian people. It is not that the Holy Father wishes to suppress popular piety or impose a rigid uniformity across the Church. Rather, it seems that his concern is to make sure that, for all facets and expressions of the faith and devotion of the people, the liturgy (what has been called theologia prima) would in fact be their origin and source.
Pope Pius also wished to reprove an increasing tendency towards antiquarianism amongst some liturgists. The Holy Father commended efforts to recover and interpret ancient liturgies and their artifacts. But he deplored efforts “to reduce everything to antiquity by every possible device” (MD, 62). The antiquarian liturgist, in a reductive and simplistic way, equates the older with the better, and the newer with the worse. But this attitude ignores the capacity for and the actuality of development in doctrine and in liturgical practice. As Pius XII wrote, “the more recent liturgical rites likewise deserve reverence and respect. They are equally the resources used by the majestic spouse of Jesus Christ to promote and procure the sanctity of man” (MD, 61).
From Letter to Council
Mediator Dei anticipated and formed part of the foundation of Sacrosanctum Concilium (SC), the Second Vatican Council’s Constitution on the Sacred Liturgy. Though it is not immediately apparent from the notes of the Constitution, a close reading of the two texts reveals the debt that the latter owes the former. The Constitution is indebted to Mediator Dei not only for its ideas, but also at times for its very words. Among the ideas that Sacrosanctum Concilium derives from MD are:
• The liturgy as exercise of Christ’s high priesthood
• The presence of Christ in the liturgy in both her ordained minister and the gathered faithful
• The presence of and encounter with the whole Christ in the liturgy (as mentioned above)
But the value of Mediator Dei lies not only in its status as a source for the teaching of Vatican II. As Father Aidan Nichols shows, Mediator Dei and Sacrosanctum Concilium have different emphases, and each develops different ideas more fully than the other. So, for example, Sacrosanctum Concilium has a distinctly more eschatological focus than the encyclical; the theme of the Lord’s coming at the Parousia is almost entirely absent from Mediator Dei. On the other hand, as Nichols describes, Mediator Dei has a deeper and richer “theology of devotion.” While the post-conciliar jettisoning of devotional life may not have been specifically demanded by Sacrosanctum Concilium, nonetheless, the Consilium which formed the Mass of Pope Paul VI and others entrusted with the implementation of liturgical reform would have done well to re-read and pay heed to the warnings of Mediator Dei.
Furthermore, had Mediator Dei’s strictures against antiquarianism been borne in mind, it might have preserved the Church from some of the excesses and “deformations” (to use Pope Benedict XVI’s word) of the post-conciliar period. The near-iconoclastic zeal for returning to an imagined pristine and primitive liturgy resulted in actions neither called for nor perhaps even anticipated by the Council Fathers, such as the all-but universal adaptation of versus populum celebration, and the abandonment and destruction of altar rails. The stripping-down of the liturgy and its attendant phenomena, as Nichols points out, was precisely what Pius XII had tried to forestall.
Meditating on Mediator Dei
Given the central role the liturgy plays in the life of the Church, Pius XII’s great liturgical encyclical is a profitable subject for renewed study. Father Nichols recalls, in his introductory essay to a recent edition of Mediator Dei, that the 50th anniversary of the letter came and went with little fanfare. We do not need a “significant” numbered anniversary to justify a return to such an important source of liturgical doctrine. In this year of its 70th anniversary, it is not intuitively obvious that the Church has settled into a post-conciliar regime which is free from misunderstanding, misdirected efforts, or missed opportunities. It may be that the importance and sweeping breadth of the Council’s teaching has tended to overshadow what has gone before. But perhaps by the 100th anniversary of the encyclical, we may be able to hear, heed, and apply the whole of its teaching.
 Pope Benedict XVI, “Homily to Commemorate the 50th Anniversary of the Death of the Servant of God Pope Pius XII.” Thursday, 9 October 2008. Accessed October 10, 2017. https://w2.vatican.va/content/benedict-xvi/en/homilies/2008/documents/hf_ben-xvi_hom_20081009_50-pio-xii.html
 Pamela Jackson, An Abundance of Graces: Reflections on Sacrosanctum Concilium. Chicago, 2004. p. 3.
 “Liturgical Briefs,” Orate Fratres, 22, no. 3: 129. As cited in Alcuin Reid, The Organic Development of the Liturgy. Farnborough, UK, 2004. p. 126.
 Lambert Beauduin, OSB, “L’encyclique Mediator Dei,” Le Maison Dieu no. 13, p. 7. As cited in Reid, 126.
 J.F. Kelly, “The Encyclical Mediator Dei,” in The New Man in Christ: National Liturgical Week. Chicago, 1948. p. 11.
 Reid, 127.
 Reid, 128.
 Joseph Ratzinger, Die sakramentale Begründung der christlichen Existenz (Freising, 1970), 5.
 See Casel, The Mystery of Christian Worship, and Other Writings, ed. Burkhard Neunheuser, OSB (Westminster, MD, 1962), esp. chs. 2-3.
 Father Aidan Nichols, A Pope and A Council on the Sacred Liturgy. Farnborough, UK, 2002. p.15.
 Nichols, 16; cf. MD, 31-32.
 Nichols, 17.
 Reid, 128.
 Jackson, 4.
 Nichols, 10.
 Nichols, 15-16.
 Nichols, 21.
 Nichols, 9.