1. I believe in the Holy Spirit
1.1 Third Person of the Blessed Trinity
In Sacred Scripture, the Holy Spirit is given various names: Gift, Lord, Spirit of God, Spirit of Truth and Paraclete, among others. Each of these terms highlights a particular characteristic of the Third Person of the Blessed Trinity. He is “Gift" because the Father and the Son send him to us gratuitously: the Spirit comes to dwell in our hearts (cf. Gal 4:6); he comes in order to remain always with us. Moreover, from him come all graces and gifts, the greatest of which is eternal life together with the other divine Persons: in him we have access to the Father through the Son.
The Spirit is called “Lord" and “Spirit of God" (names used by Sacred Scripture only for God) because he is God with the Father and the Son. He is the “Spirit of Truth" because he teaches us all that Christ has revealed in its fullness, and he guides and sustains the Church in the truth (cf. Jn 15:26; 16:13-14). He is the “other" Paraclete (Consoler, Advocate) promised by Christ, who is the first Paraclete (the Greek text speaks of the “other" Paraclete, and not a “distinct" paraclete, to stress the communion and continuity between Christ and the Spirit).
In the Nicene-Constantinople Creed we pray Et in Spiritum Sanctum, Dominum et vivificantem: qui ex Patre [Filioque] procedit. Qui cum Patre et Filio simul adoratur, et conglorificatur: qui locutus est per Prophetas. With these phrases the Fathers of the Council of Constantinople highlighted some of the biblical expressions for naming the Spirit. By the expression “giver of life," reference is made to the gift of divine life to mankind. As Lord and giver of life, he is God, with the Father and the Son, and therefore receives the same adoration they do. The last phrase points to the mission the Spirit carries out among men: he has spoken through the prophets. The prophets are those who, moved by the Spirit, spoke in God's name to stir his people to convert. The revelation by the Spirit in the Old Testament prophecies reaches its fullness in the mystery of Jesus Christ, God's definitive Word.
“There are many symbols of the Holy Spirit: living water which springs from the wounded heart of Christ and which quenches the thirst of the baptized; anointing with oil, which is the sacramental sign of Confirmation; fire which transforms what it touches; the cloud, dark or luminous, in which the divine glory is revealed; the imposition of hands by which the Holy Spirit is given; the dove which descended on Christ at his baptism and remained with him" ( Compendium, 139).
1.2 Mission of the Holy Spirit
The Third Person of the Blessed Trinity “is at work with the Father and the Son from the beginning to the completion of the plan for our salvation. But in these 'end times,' ushered in by the Son's redeeming Incarnation, the Spirit is revealed and given, recognized and welcomed as a person" (Catechism, 686). Through the action of the Spirit, the Son of God became man in the most pure womb of the Blessed Virgin Mary and received his anointing as Messiah. Christ, in turn, “revealed the Spirit in his teaching, fulfilled the promises made to the Fathers, and bestowed him upon the Church at its birth when he breathed on the apostles after the Resurrection" (Compendium, 143). On Pentecost, the Spirit was sent to remain continually in the Church, the Mystical Body of Christ, vivifying it and guiding it with his gifts and his presence. Therefore the Church is also said to be the Temple of the Holy Spirit, who is, as it were, the soul of the Church.
On the day of Pentecost, the Spirit descended on the apostles and the first disciples, showing with external signs the giving of life to the Church founded by Christ. “The mission of Christ and of the Spirit became the mission of the Church, which is sent to proclaim and spread the mystery of the communion of the Trinity" (Compendium, 144). The Spirit initiates in the world the “last days," the time of the Church.
The vivifying of the Church by the Holy Spirit guarantees that all that Christ said and taught during the days he lived on earth until his Ascension is always preserved without loss and ever more deeply understood.  Furthermore, through the sacraments, the Spirit sanctifies the Church and the faithful, and enables the Church to continually bring souls to God. 
“In the indivisible Trinity, the Son and the Spirit are distinct but inseparable. From the very beginning until the end of time, when the Father sends his Son he also sends his Spirit who unites us to Christ in faith so that as adopted sons we can call God 'Father' (Rom 8:15). The Spirit is invisible but we know him through his actions, when he reveals the Word to us and when he acts in the Church" ( Compendium, 137).
1.3 How do Christ and the Holy Spirit act in the Church?
Through the Church's sacraments, Christ communicates his Spirit to the members of his Body, and offers them God's grace, which bears the fruit of new life in the Spirit. The Holy Spirit also grants special graces to some Christians for the good of the whole Church. He is also the Teacher who reminds all Christians what Christ revealed (cf. Jn 14:25 ff.).
“The Spirit builds, animates and sanctifies the Church. As the Spirit of Love, he restores to the baptized the divine likeness that was lost through sin and causes them to live in Christ the very life of the Holy Trinity. He sends them forth to bear witness to the Truth of Christ and he organizes them in their respective functions so that all might bear 'the fruit of the Spirit' (Gal 5:22) (Compendium, 145).
2. I believe in the Holy Catholic Church
2.1 Revelation of the Church
The Church is a mystery (cf. Rom 16:25-27), that is, a reality in which God and men come into contact and enter into communion. The term “church" comes from the Greek “ekklesia," which means the assembly of those who are “convoked." In the Old Testament it was the term used to translate “quahal Yaweh," the assembly gathered by God to honor him with due worship. Examples of this were the Sinaitic assembly, and the assembly convoked in the times of King Josiah to praise God and return to the purity of the Law. In the New Testament, in continuity with the Old Testament, it has several different meanings; but it especially designates the people God calls and gathers together from all over the world to form the assembly of those who, through faith in his Word and Baptism, have become children of God, members of Christ and temple of the Holy Spirit (cf. Catechism, 777, Compendium, 147).
In Sacred Scripture the Church receives a number of different names, each of which expresses some particular aspect of the mystery of the communion of God with mankind. “People of God" is a title that Israel had received. When applied to the Church, the “new Israel," it signifies that God did not choose to save men as isolated individuals, but rather by making them into one people gathered into unity by the unity of the Father, the Son and the Holy Spirit, that they might acknowledge him in truth and serve him in holiness.  It also signifies that the Church has been chosen by God as a visible community among the nations, journeying toward its final homeland. In this people, all have the common dignity of being God's children, a common mission to be salt of the earth, and a common end, which is the Kingdom of God. And all share in the three functions of Christ, namely, the priestly, prophetic and royal (cf. Catechism, 782-786).
When we say that the Church is the “Body of Christ," we mean that Christ, by sending the Holy Spirit, unites the faithful to himself in an intimate way, especially in the Eucharist. He incorporates them into himself through the Spirit, so that they grow in union through charity and form a single body, while preserving the diversity of members and functions. By this term we also express that the health or infirmity of any member has repercussion on the whole body (cf. 1 Cor 12:1-24), and that the faithful, as members of Christ, are his instruments for acting in the world (cf. Catechism, 787-795). The Church is also called the “Bride of Christ" (cf. Eph 5:26 ff.), which highlights both the union and the distinction between Christ and his Church. This name also implies that God's covenant with mankind is definitive, because God is faithful to his promises, and the Church, in turn, faithfully corresponds by being a fruitful Mother of all the sons and daughters of God.
The Church is also the “temple of the Holy Spirit," since he lives in the body of the Church and builds it up in charity through the Word of God, the sacraments, the virtues and the charisms.  Since the true temple of the Holy Spirit was Christ (cf. Jn 2:19-22), this image also implies that each Christian is a temple of the Holy Spirit. The charisms are “special gifts of the Holy Spirit which are bestowed on individuals for the good of others, the needs of the world, and in particular for the building up of the Church. The discernment of charisms is the responsibility of the Magisterium" (Compendium, 160; cf. 1 Thess 5:20-22).
“The Church finds her origin and fulfillment in the eternal plan of God. She was prepared for in the Old Covenant with the election of Israel, the sign of the future gathering of all the nations. Founded by the words and actions of Jesus Christ, fulfilled by his redeeming death and Resurrection, the Church has been manifested as the mystery of salvation by the outpouring of the Holy Spirit at Pentecost. She will be perfected in the glory of heaven as the assembly of all the redeemed of the earth" ( Compendium, 149; cf. Catechism, 778).
God in revealing his eternal plan of salvation also shows us how he intends to carry it out. This plan was not achieved in one action; rather he prepared mankind over time to accept the salvation that was fully revealed in Christ. This offering of salvation in communion with God and in unity amongst men and women was definitively granted through the gift of the Holy Spirit poured out in the hearts of believers, putting them into personal and permanent contact with Christ. On becoming children of God in Christ, we recognize ourselves as brothers and sisters of the other children of God. There is no fraternity or unity among men that is not based on this common divine filiation offered us by the Father in Christ: there is no fraternity without a common Father, whom we reach through the Holy Spirit.
The Church was not founded by men, nor is it a noble human response to the work of salvation achieved by God in Christ. In the mysteries of Christ's life, the Man anointed by the Spirit fulfilled the promises announced in the Law and Prophets. We can also say that the founding of the Church coincides with the life of Jesus Christ; the Church takes form in relation to Christ's mission among men, and for men. There is no particular moment when Christ can be said to have founded the Church, for he founded it throughout his entire life, from the Incarnation right up to his death, through his Resurrection, Ascension and sending of the Paraclete. Throughout his life, Christ, in whom the Spirit dwells, was making known how his Church was to be. After his Ascension, the Spirit was sent to the Church and remains in her, uniting her to Christ's mission, reminding her of what the Lord has revealed, and guiding her though history towards her fullness. The Spirit is the cause of the Christ's presence in his Church through the sacraments and the Word, and continually adorns it with different hierarchical and charismatic gifts.  By his presence, the Lord's promise to always be with us until the end of time is fulfilled (cf. Mt 28:20).
Vatican Council II reclaimed an ancient expression in describing the Church as “communion." This term indicates that the Church is the extension to mankind of the intimate communion of the Blessed Trinity and that on earth she is already communion with the Trinity, though not yet in all its fullness. Furthermore, the Church is for all men and women the sign and instrument of this communion: through her we participate in God's intimate life and belong to God's family as sons in the Son through the Spirit.  This is accomplished in a specific manner in the sacraments, principally the Eucharist, which also is frequently called communion (cf. 1 Co 10:16). Lastly, the Church is also called “communion" because she engenders a spirit of prayer (cf. Catechism, 2655, 2672, 2790).
2.2 Mission of the Church
The Church has to proclaim and establish among all people the Kingdom of God inaugurated by Christ. On earth she is the seed and beginning of this Kingdom. After his Resurrection, the Lord sent out his Apostles to preach the Gospel, baptize and teach all nations to observe what he had commanded (cf. Mt 28:18 ff.). The Lord gave his Church the same mission that the Father had entrusted to him (cf. Jn 20:21). From the Church's beginning, this mission was accomplished by all Christians (cf Acts 8:4; 11, 19), even with the sacrifice of their lives in many cases. The Lord's missionary mandate has its source in the eternal love of God, who sent his Son and his Spirit because he wanted all men to be saved and come to the knowledge of the truth (1 Tim 2:4).
This mission contains the Church's three functions on earth: the munus propheticum (to proclaim the good news of salvation in Christ), the munus sacerdotale (to make present and transmit the saving life of Christ through the sacraments), and the munus regale (to help Christians fulfill their mission and grow in holiness). Although all the faithful share in the same mission, not all have the same role. Some of them were chosen by Christ to exercise particular functions such as that of the Apostles and their successors; these are conformed to Christ the Head of the Church in a specific and exclusive manner through the sacrament of Orders.
Since the Church has received from God a saving mission on earth for men and has been prepared by him to carry it out, she is said to be the universal sacrament of salvation; for she has as her aim the glory of God and the salvation of mankind (cf. Catechism, 775). She is the sacrament of salvation because she is the sign and instrument of reconciliation and communion of mankind with God and the unity of all men and women.  The Church is also said to be a mystery since in her visible reality, a spiritual and divine reality perceivable only by faith is made present and active.
The affirmation that “outside the Church there is no salvation" means that all salvation comes from Christ the Head through the Church, which is his Body. Those could not be saved who, knowing that the Catholic Church was founded by Christ for the salvation of men, would refuse to enter it or to remain in it. At the same time, thanks to Christ and his Church, those can attain salvation who, through no fault of their own, do not know the Gospel of Christ and his Church, but who nonetheless seek God with a sincere heart, and strive under the influence of grace to fulfill his will as it is known to them through the dictates of their conscience. All that is good and true in other religions comes from God and can prepare for the reception of the Gospel and lead towards the unity of mankind in the Church of Christ (cf. Compendium, 170 and ff.)
2.3 Properties of the Church: one, holy, catholic, apostolic
The properties of the Church are the four characteristics that indicate essential features of the Church and her mission (cf. Catechism, 811). These are found in many of the Symbols of the Faith from very early times of the Church. All these properties are a gift of God that entails a task for Christians to carry out. “The Church is one because she has as her source and exemplar the unity of the Trinity of Persons in one God. As her Founder and Head, Jesus Christ re-established the unity of all people in one body. As her soul, the Holy Spirit unites all the faithful in communion with Christ" ( Compendium, 161). This unity is shown by the fact that the faithful profess the same faith, celebrate the same sacraments, are united in a single hierarchy, have one common hope and one and the same charity. “The Church, constituted and organized as a society in the present world, subsists in the Catholic Church, which is governed by the successor of Peter and by the bishops in communion with him."  Only in the Church can the fullness of the means of salvation be obtained, since our Lord entrusted the blessings of the New Covenant to the apostolic college alone, whose head is Peter.
In the non-catholic churches and communities many elements of sanctification and truth can be found. All these blessings come from Christ and lead to catholic unity. The Holy Spirit uses these as means of salvation since their power derives from the fullness of grace and truth that Christ entrusted to the Catholic Church (cf. Catechism, 819). Members of these churches and communities are incorporated into Christ by Baptism, so we recognize them as brothers and sisters. We can help foster unity by drawing closer to Christ ourselves and helping other Christians to come closer to him; by seeking unity in what is necessary, freedom in what is not essential, and charity in everything;  by making God's house more attractive for others; and by increasing veneration and respect for the Pope and the hierarchy, assisting them and following their teachings.
The ecumenical movement is an ecclesial task by which the restoration of unity among Christians is sought in the one and only Church founded by Christ. This is the Lord's desire (cf. Jn 17:21). It is achieved through prayer, conversion of heart, fraternal knowledge and theological dialogue.
The Church is Holy since the All-Holy God is her author; Christ has given himself for her to sanctify her and make her the fount of sanctification, and the Holy Spirit vivifies her with charity. Since she has the fullness of the means of salvation, holiness is the vocation of each of her members and the aim of all her activity. She is holy because she constantly yields the fruit of holiness on earth and because her holiness is the source of the sanctification of her children—although here on earth all must recognize themselves as sinners ever in need of conversion and purification. The Church's faithful are called to strive always to grow in holiness, by personal conversion and the struggle to become more like Christ. The Church is holy also because of the holiness attained by her members who are in heaven, especially the Blessed Virgin Mary, who are their models and intercessors (cf. Catechism, 823-829).
The Church is Catholic, that is, universal, because Christ is present in her and she herself preserves and administers all the means of salvation entrusted to her by Christ—a treasure she has received and transmits with total integrity. She is universal because her mission embraces the whole human race, and she has the capacity to adapt to every setting, elevating and improving any culture. Catholicity increases in extension and intensity as the Church's mission grows and develops. Every particular Church, that is, every portion of God's people that shares in the communion of faith and the sacraments, with its bishop ordained in apostolic succession, and formed in the image of the universal Church and in communion with the whole Church (which precedes the particular church ontologically and chronologically) is catholic.
Since her mission embraces all humanity, each person, in various ways, belongs to or at least is ordered to the catholic unity of the People of God. “Fully incorporated into the Church are those who, possessing the Spirit of Christ, are joined to the Church by bonds of the profession of faith, the sacraments, ecclesiastical government and communion" ( Compendium, 168). The baptized that do not persevere in charity, although incorporated into the Church, belong to her only in body but not in heart. “The baptized that do not fully enjoy this catholic unity are in a certain, though imperfect, communion with the Catholic Church" ( Compendium, 168).
The Church is Apostolic because Christ has built her on the Apostles, chosen witnesses of the Resurrection and the foundation of his Church, and because with the assistance of the Holy Spirit, she teaches, watches over and faithfully transmits the deposit of faith received from the Apostles. The Church is apostolic also by reason of her structure, since she is taught, sanctified and guided until Christ's return by the apostles and their successors, the bishops, in communion with the successor of Peter. "Apostolic succession is the transmission by means of the sacrament of Holy Orders of the mission and power of the Apostles to their successors, the bishops. Thanks to this transmission, the Church remains in communion of faith and life with her origin, while through the centuries she carries on her apostolate for the spread of the Kingdom of Christ on earth" (Compendium, 176). All the Church's members, according to their specific function, share in the mission received by the Apostles to bring the Gospel to the whole world. The Christian vocation, by its very nature, is a vocation to the apostolate (cf. Catechism, 683).
Miguel de Salis Amaral
Catechism of the Catholic Church, 683, 688; 731-741.
Compendium of the Catechism of the Catholic Church, 136-146.
John Paul II, Enc. Dominum et vivificantem, 18 May 1986, 3-26.
John Paul II, Catechesis on the Holy Spirit, 8 December 1989.
St Josemaria, Homily The Great Unknown, in Christ Is Passing By, 127-138.
Catechism of the Catholic Church, 748-945.
Compendium of the Catechism of the Catholic Church, 147-193.
St Josemaria, Homily Loyalty to the Church , in In Love with the Church.
 Cf. Vatican Council II, Const. Dei Verbum, 8.
 “The solemn coming of the Holy Spirit on Pentecost was not an isolated event. There is hardly a page in the Acts of the Apostles where we fail to read about him and the action by which he guides, directs and enlivens the life and work of the early Christian community … The profound reality which we see in the texts of holy Scripture is not a remembrance from the past, from some golden age of the Church which has since been buried in history. Despite the weaknesses and the sins of every one of us, it is the reality of today's Church and the Church of all time" (St Josemaria, Christ is Passing By, nos. 127-128.
 Cf. Vatican Council II, Lumen Gentium, 4 and 9; St Cyprian, De Orat. Dom., 23 (CSEL 3, 285).
 “When you invoke God the Father, then, remember that the Spirit is the one who has given you this prayer by stirring your soul. If the Holy Spirit did not exist, there would be no word of wisdom or knowledge at all in the Church., because it is written: the word of wisdom is given by the Spirit (1 Cor 12:8)…If the Holy Spirit were not present, the Church would not exist. But, if the Church exists, it is certain that the Holy Spirit is not lacking" (St John Crysostom, Sermones paneghrici in solemnitates D.N. Iesu Christ, hom. 1, De Sancta Pentecostes , . no. 3-4, PG 50, 457).
 Cf. Vatican Council II, Lumen Gentium, 4 and 12.
 Cf. Vatican Council II, Gaudium et Spes, 22.
  Cf. Vatican Council II, Lumen Gentium, 1.
 Ibidem, 8,
 Cf. Vatican Council II, Gaudium et Spes, 92