« MYSTICI CORPORIS ». – Initial words of the encyclical of Pius XII, dated 29 June 1943 (AAS, 36 [1943], pp. 193–248), in which the doctrine of the Mystical Body is developed. The Pontiff was induced to promulgate this solemn document by the memorandum sent by Msgr. Corrado Gröber, archbishop of Freiburg (in Breisgau), to the Holy See and to the German bishops, concerning the errors disseminated in Germany on the subject (cf. J. Froger, L'encyclique Mediator Dei, in La pensée catholique. Cahiers de synthèse, 7 [1949], pp. 56–76, especially pp. 65–66, where no. 11 of Gröber’s letter is reproduced, in which the doctrinal exaggerations concerning the Mystical Body are clearly indicated). The encyclical is a precise and detailed response to the individual points at issue, but generally given in implicit form, as an aside within a broader discourse; indeed, in the serene development of its imposing doctrinal structure, the response acquires a particular persuasive force for those who have erred and a special probative strength for those who have remained within the bounds of orthodoxy.
The encyclical begins from the concept of the Church as a body, whose prerogatives it sets forth: one, undivided, visible, organically and hierarchically compact, endowed with means of sanctification (the Sacraments) and constituted by definite members (not excluding sinners); it then demonstrates that this body is Christ’s, « corpus Christi », because Jesus Christ is a) its founder: through evangelical preaching, redemption by the Cross, and its promulgation on the day of Pentecost; b) its head: by reason of his pre-eminent dignity, invisible and visible direction (through the pope and bishops), mutual interdependence, conformity of nature and Grace with the body, fullness of supernatural charisms, and influence upon the entire organism through ontological means (sanctifying) and psychological means (enlightening); c) its sustainer, through his ministers, who build it up from without, and the Holy Spirit, who, as the soul of the Mystical Body, is its inner principle of cohesion and the regulator of all its vital currents; d) its savior, since he acquired all the members of the Church sanguine suo (part 1). From these relations of Christ with the Church there emerges the intimate, mysterious union of all the faithful with Jesus; its juridical, social, psychological, ontological, and sacramental bonds, especially Eucharistic ones, are then illustrated (part 2). As a corollary to the matter discussed, the Pope condemns false mysticism and quietism, as well as certain errors concerning confession and prayer, concluding with a fervent appeal to love the Church (part 3). A moving epilogue on Mary as Mother of the Mystical Body closes the great document.
The encyclical frequently contains assertions of extraordinary theological importance, almost pronuntiata maiora of the Magisterium in modern ecclesiology, for example: the identity of the Mystical Body with the Roman Catholic Church; the conditions Church (v.); the condemnation of the vivisection between « Rechtskirche » (Ecclesia iuris) and « Liebeskirche » (Ecclesia amoris); the Holy Spirit as the soul of the Mystical Body; the close relations between the internal and external government of the same organism; ecclesiological theandrism; the condemnation of every form of pan-Christism (against Pelz); Maria Mater Ecclesiae.
This distinguished document is the glorious epilogue of that movement which, taking shape in Germany through the work of J. A. Möhler (v.), influenced all nineteenth-century ecclesiology (C. Passaglia, Cl. Schrader, J. B. Franzelin, M. J. Scheeben), as an implicit response to the materialistic conception of human solidarity. When, after the war of 1914–18, the Catholic and Marxist conceptions confronted one another throughout Europe, almost an ideological and chronological coincidentia oppositorum, the theme of the Mystical Body was once again particularly keenly felt: works of broad erudition and directed toward a constructive synthesis arose (J. Anger, F. Jürgersmeier, Feckes, Wikenhauser, Grivec, E. Mura, Koster, E. Mersch, L. Malevez, S. Tromp, Congar). Amid such fervor of study, enthusiasms and excesses of form and substance are understandable. The encyclical gathers together and gives value to the finest elements of this theology in fieri; it does not suppress the movement, but strengthens it by eliminating its principles of dissolution. It brings one epoch of ecclesiological theology to a close, in order to begin another that is more secure and more fruitful.