Hermann Schmidt opens his Hebdomada Sancta with the lapidary phrase: "Pascha est cor liturgiae." The heart of the liturgy is the Paschal Mystery of Christ's death, Resurrection and Ascension, accomplished once and for all in Christ the Head, and extended by means of the liturgy to all his members throughout history. Dame Aemiliana Löher, the Benedictine of Herstelle writes in The Great Week, a book I never tire of reading at this time of the year, that, "It will never be possible for the Church in her liturgy to make anything else present or anything else the subject of her celebration than the Pasch of Christ."
All Christian worship is but a continuous celebration of the Pasch: the sun, dawning each day, draws in its course an uninterrupted train of Eucharists; every celebration of Mass prolongs the Pasch. Each day of the liturgical year, and within each day, every instant of the Church's sleepless vigil, continues and renews the Pasch. (Louis Bouyer, Le Mystère Pascal)
The Liturgy is the Church's Primary Theology
The Paschal Mystery is the ultimate and unrepeatable word from God, to God and about God. Actualized in the liturgy, the Paschal Mystery is the substance and expression of the Church's theologia prima, the ground and reference of her theologia secunda. The complement of Schmidt's aphorism Pascha est cor liturgiae is that the Pasch of Christ, sacramentally mediated in the liturgy, is the wellspring of a living, doxological theology, the only kind of theology that a monk can embrace fully and find himself at home in.
The Mystery of Christ
In repeating the enactment of the liturgy, the Church has access to the "unique, unrepeatable mystery of Christ"; day after day, week after week, and year after year, the Church is caught up in the transforming glory of the Paschal Mystery of Christ, her Bridegroom and Head. Through the actio, the Paschal Mystery irrigates and transforms all of human life, healing those who partake of the sacraments and drawing the Church, already here and now, into the communion of the risen and ascended Christ with the Father in the Holy Spirit. Because it is the heart of the liturgy, the Pasch of the Lord is the heart of theology, and the heart of Christian piety as well.
The Sacred Triduum
The Paschal Triduum begins with the Evening Mass In Cena Domini on Maundy Thursday, continues through the Friday of the Lord's Passion, reaches its summit in the Solemn Paschal Vigil, and comes to a close with Sunday Vespers of the Lord's Resurrection.