The Christian Celebration With the incarnation of Christ, the eternal enters human time and makes it holy. The Church becomes the “space” that makes room for the presence of God (cf. PNLO 3). The liturgy, which is celebrated in time and in space, makes the salvation won by Christ present for all times in the “today” of the Christian celebration. By opening up the deepest dimensions of the concept of “celebration”, the present work goes on to cover the areas of Christian celebration in relation to space and time, in which the ars celebrandi finds its way of expressing the mystery: the celebrating assembly as the subject of the liturgical action; the Word of God as proclamation of salvation in the sound of words and in the animation given them by the Holy Spirit; time as the “place” in which the liturgy reveals the eternal; the liturgical year in which the Paschal Mystery of Christ is gradually and consciously presented and celebrated; the Liturgy of the Hours as the public prayer of the People of God, which extends the culmen of the eucharistic celebration; liturgical space, which in the mystagogy of time and of the rites, manifests the one faith in the Risen One. It is a piece of research which draws continually from its direct contact with the sources, and demonstrates its concern to return to the principles of the Council and to offer a serious and new liturgical theological reflection on them.