PIUS XII 1939-1958
The Full Notion of Liturgy *
[From the same Encyclical, “Mediator Dei,” November 20, 1947]
2298 The sacred Liturgy, then, constitutes the public worship which our Redeemer, the Head of the Church, has shown to the heavenly Father; and which the society of the faithful in Christ attribute to their Founder, and through Him to the eternal Father; and, to sum up briefly, it constitutes the public worship of the mystical body of Jesus Christ, namely, the Head and its members.
Therefore, they wander entirely away from the true and full notion and understanding of the Sacred Liturgy, who consider it only as an external part of divine worship, and presented to the senses; or as a kind of apparatus of ceremonial proprieties; and they no less err who think of it as a mere compendium of laws and precepts, by which the ecclesiastical Hierarchy bids the sacred rites to be arranged and ordered.