Part II: The Guiding Principles of the Constitution
5. The guiding principles of the constitution, which were the basis of the reform, remain fundamental in the task of leading the faithful to an active celebration of the mysteries, "the primary and indispensable source of the true Christian spirit."  Now that the greater part of the liturgical books has been published, translated and brought into use, it is still necessary to keep these principles constantly in mind and to build upon them.
A. The Re-enactment of the Paschal Mystery
6. The first principle is the re-enactment of the paschal mystery of Christ in the liturgy of the Church based on the fact that "it was from the side of Christ as he slept upon the cross that there issued forth the sublime sacrament of the whole Church."  The whole of liturgical life gravitates about the eucharistic sacrifice and the other sacraments, in which we draw upon the living springs of salvation (cf. Is. 12:3).  Hence we must have a sufficient awareness that through the "paschal mystery we have been buried with Christ in baptism so that we may rise with Him to a new life."  When the faithful participate in the Eucharist, they must understand that truly "each time we offer this memorial sacrifice, the work of our redemption is accomplished,"  and to this end bishops must carefully train the faithful to celebrate every Sunday the marvelous work that Christ has wrought in the mystery of His passover, in order that they likewise may proclaim it to the world.  In the hearts of all, bishops and faithful, Easter must regain its unique importance in the liturgical year, so that it really is the feast of feasts.
Since Christ's death on the cross and His resurrection constitute the content of the daily life of the Church  and the pledge of His eternal passover,  the liturgy has as its first task to lead us untiringly back to the Easter pilgrimage initiated by Christ, in which we accept death in order to enter into life.
7. In order to re-enact His paschal mystery, Christ is ever present in His Church, especially in liturgical celebrations.  Hence the liturgy is the privileged place for the encounter of Christians with God and the One whom He has sent, Jesus Christ. (cf. Jn. 17:3).
Christ is present in the Church assembled at prayer in His name. It is this fact which gives such a unique character to the Christian assembly, with the consequent duties not only of brotherly welcome but also of forgiveness (cf. Mt. 5:23-24), and of dignity in behavior, gesture and song.
Christ is present and acts in the person of the ordained minister who celebrates.  The priest is not merely entrusted with a function, but in virtue of the ordination received he has been consecrated to act in persona Christi. To this consecration there must be corresponding disposition, both inward and outward, also reflected in liturgical vestments, in the place which he occupies and in the word which he utters.
Christ is present in His word as proclaimed in the assembly and which, commented upon in the homily, is to be listened to in faith and assimilated in prayer. All this must derive from the dignity of the book and of the place appointed for the proclamation of the word of God and from the attitude of the reader, based upon an awareness of the fact that the reader is the spokesman of God before his or her brothers and sisters.
Christ is present and acts by the power of the Holy Spirit in the sacraments and, in a special and pre-eminent fashion (sublimiori modo), in the sacrifice of the Mass under the eucharistic species,  also when these are reserved in the tabernacle apart from the celebration with a view to communion of the sick and adoration by the faithful.  With regard to this real and mysterious presence, it is the duty of pastors to recall frequently in their catechetical instructions the teaching of the faith, a teaching that the faithful must live out and that theologians are called upon to expound. Faith in this presence of the Lord involves an outward sign of respect toward the Church, the holy place in which God manifests himself in mystery (cf. Ex. 3:5). especially during the celebration of the sacraments: Holy things must always be treated in a holy manner.
The Reading of the Word of God
8. The second principle is the presence of the word of God.
The constitution Sacrosanctum Concilium sets out likewise to restore a "more abundant reading from Holy Scripture, one more varied and more appropriate."  The basic reason for this restoration is expressed both in the Constitution on the Liturgy, namely, so that "the intimate link between rite and word" may be manifested,  and also in the Dogmatic Constitution on Divine Revelation, which teaches: "The Church has always venerated the divine Scriptures, just as she has venerated the very body of the Lord, never ceasing above all in the sacred liturgy to nourish herself on the bread of life at the table both of the word of God, and of the body of Christ, and to minister it to the faithful."  Growth in liturgical life and consequently progress in Christian life cannot be achieved except by continually promoting among the faithful, and above all among priests, a "warm and living knowledge of Scripture."  The word of God is now better known in the Christian communities, but a true renewal sets further and ever new requirements: Fidelity to the authentic meaning of the Scriptures, which must never be lost from view, especially when the Scriptures are translated into different languages; the manner of proclaiming the word of God so that it may be perceived for what it is; the use of appropriate technical means, the interior disposition of the ministers of the word so that they carry out properly their function in the liturgical assembly;  careful preparation of the homily through study and meditation; effort on the part of the faithful to participate at the table of the word; a taste for prayer with the psalms; a desire to discover Christ - like the disciples at Emmaus - at the table of the word and the bread. 
The Self-Manifestation of the Church
9. Finally, the council saw in the liturgy an epiphany of the Church: It is the Church at prayer. In celebrating divine worship the Church gives expression to what she is: one, holy, catholic and apostolic.
The Church manifests herself as one, with that unity which comes to her from the Trinity,  especially when the holy people of God participates "in the one Eucharist, in one and the same prayer, at the one altar, presided over by the bishop surrounded by his presbyterate and ministers."  Let nothing disrupt or obscure in the celebration of the liturgy this unity of the Church!
The Church expresses the holiness that comes to her from Christ (cf. Eph. 5:26-27) when, gathered in one body by the Holy Spirit,  who makes holy and gives life,  she communicates to the faithful by means of the Eucharist and the other sacraments all the graces and blessings of the Father. 
In liturgical celebration the Church expresses her catholicity, since the Spirit of the Lord gathers together in her people of all languages in the profession of the same faith  and from East and West presents to God the Father the offerings of Christ and offers herself together with Him. 
In the liturgy the Church manifests herself as apostolic, because the faith that she professes is founded upon the witness of the apostles; because in the celebration of the mysteries, presided over by the bishop, successor of the apostles, or by a minister ordained in the apostolic succession, she faithfully hands on what she has received from the apostolic tradition; and because the worship which she renders to God commits her to the mission of spreading the Gospel in the world.
Thus it is especially in the liturgy that the mystery of the Church is proclaimed, experienced and lived.