Today in Mediator Dei we read something along the lines of what we’ve read in Pope Francis with regard to evangelization: the importance of cooperating with God’s grace and initiative in the world. We also have the seed of the hallmark of conciliar liturgical reform: full, active, and conscious participation. It’s more than a novelty. It’s far from a dumbing down of beauty and quality. It touches at the heart of what it means to be a Christian actively seeking God and the sanctifying grace offered to people.
78. The cooperation of the faithful is required so that sinners may be individually purified in the blood of the Lamb. For though, speaking generally, Christ reconciled by His painful death the whole human race with the Father, He wished that all should approach and be drawn to His cross, especially by means of the sacraments and the eucharistic sacrifice, to obtain the salutary fruits produced by Him upon it. Through this active and individual participation, the members of the Mystical Body not only become daily more like to their divine Head, but the life flowing from the Head is imparted to the members, so that we can each repeat the words of St. Paul, “With Christ I am nailed to the cross: I live, now not I, but Christ liveth in me.”[Gal. 2:19-20] We have already explained sufficiently and of set purpose on another occasion, that Jesus Christ “when dying on the cross, bestowed upon His Church, as a completely gratuitous gift, the immense treasure of the redemption. But when it is a question of distributing this treasure, He not only commits the work of sanctification to His Immaculate Spouse, but also wishes that, to a certain extent, sanctity should derive from her activity.”[Encyclical Letter, Mystici Corporis, June 29, 1943]
Human cooperation is more than a mental affirmation of Christian knowledge. This section seems to reinforce the notion that a believer is active in faith. In part, it is through active participation that a follower of Christ responds to the invitation to sanctity.
In the liturgy, I think this is an appropriate grounding for lay participation as we understand it in the modern Roman Rite. Liturgical leaders can do no less than to facilitate this cooperation with grace.
Pope Pius XII states that this is not a new idea for him; he cites his previous encyclical letter Mystici Corporis on this point.