In his 1947 encyclical on the sacred liturgy, Mediator Dei, Pope Pius XII called for a deeper participation by all involved in the liturgy-aparticipation that would go beyond mere physical presence or grudging attention and lead to both deeper understanding and richer involvement-and he commended several practices in use at the time to draw lay people into a more conscious and active participation in Mass. His description of the need for both "exterior" and "interior" participation laid the groundwork for the Second Vatican Council's call for "fully conscious, and active participation in liturgical celebrations" as "the aim to be considered before all else" in the restoration and promotion of the sacred liturgy. These excerpts from the Vatican's English translation of Mediator Dei are taken from paragraphs 23-26, 105, and 194.
The worship rendered by the Church to God must be, in its entirety, interior as well as exterior. It is exterior because human nature as a composite of body and soul requires it to be so. Likewise because divine Providence has disposed that "while we recognize God visibly, we may be drawn by him to love of things unseen" (Roman Missal, Christmas Preface). Every impulse of the human heart, besides, expresses itself naturally through the senses; and the worship of God, being the concern not merely of individuals but of the whole community of mankind, must therefore be social as well. This obviously it cannot be unless religious activity is also organized and manifested outwardly. Exterior worship, finally, reveals and emphasizes the unity of the mystical Body, feeds new fuel to its holy zeal, fortifies its energy, intensifies its action day by day: "for although the ceremonies themselves can claim no perfection or sanctity in their own right, they are, nevertheless, the outward acts of religion, designed to rouse the heart, like signals of a sort, to veneration of the sacred realities, and to raise the mind to meditation on the supernatural. They serve to foster piety, to kindle the flame of charity, to increase our faith and deepen our devotion. They provide instruction for simple folk, decoration for divine worship, continuity of religious practice. They make it possible to tell genuine Christians from their false or heretical counterparts" (Bona, De divina psalmodia, XIX: 3, 1).
But the chief element of divine worship must be interior. For we must always live in Christ and give ourselves to him completely, so that in him, with him, and through him the heavenly Father may be duly glorified. The sacred liturgy requires, however, that both of these elements be intimately linked with each another. This recommendation the liturgy itself is careful to repeat, as often as it prescribes an exterior act of worship. . . . Otherwise religion clearly amounts to mere formalism, without meaning and without content. …