The following are selections from the Catechism of the Catholic Church, pertaining to Mary. The numbers at the beginning of the paragraphs refer to the numbering system of the CCC. If you click through that link, just enter the number in the search to be taken to that section of the CCC.
484 The Annunciation to Mary inaugurates "the fullness of time,"119 the time of the fulfillment of God's promises and preparations. Mary was invited to conceive him in whom the "whole fullness of deity" would dwell "bodily."120 The divine response to her question, "How can this be, since I know not man?" was given by the power of the Spirit: "The Holy Spirit will come upon you." 121
485 The mission of the Holy Spirit is always conjoined and ordered to that of the Son.122 The Holy Spirit, "the Lord, the giver of Life," is sent to sanctify the womb of the Virgin Mary and divinely fecundate it, causing her to conceive the eternal Son of the Father in a humanity drawn from her own.
486 The Father's only Son, conceived as man in the womb of the Virgin Mary, is "Christ," that is to say, anointed by the Holy Spirit, from the beginning of his human existence, though the manifestation of this fact takes place only progressively: to the shepherds, to the magi, to John the Baptist, to the disciples. 123 Thus the whole life of Jesus Christ will make manifest "how God anointed Jesus of Nazareth with the Holy Spirit and with power." 124
487 What the Catholic faith believes about Mary is based on what it believes about Christ, and what it teaches about Mary illumines in turn its faith in Christ.
488 "God sent forth his Son," but to prepare a body for him, 125 he wanted the free co-operation of a creature. For this, from all eternity God chose for the mother of his Son a daughter of Israel, a young Jewish woman of Nazareth in Galilee, "a virgin betrothed to a man whose name was Joseph, of the house of David; and the virgin's name was Mary": 126
The Father of mercies willed that the Incarnation should be preceded by assent on the part of the predestined mother, so that just as a woman had a share in the coming of death, so also should a woman contribute to the coming of life. 127
489 Throughout the Old Covenant the mission of many holy women prepared for that of Mary. At the very beginning there was Eve; despite her disobedience, she receives the promise of a posterity that will be victorious over the evil one, as well as the promise that she will be the mother of all the living.128 By virtue of this promise, Sarah conceives a son in spite of her old age.129 Against all human expectation God chooses those who were considered powerless and weak to show forth his faithfulness to his promises: Hannah, the mother of Samuel; Deborah; Ruth; Judith and Esther; and many other women.130 Mary "stands out among the poor and humble of the Lord, who confidently hope for and receive salvation from him. After a long period of waiting the times are fulfilled in her, the exalted Daughter of Sion, and the new plan of salvation is established."131
490 To become the mother of the Savior, Mary "was enriched by God with gifts appropriate to such a role."132 The angel Gabriel at the moment of the annunciation salutes her as "full of grace."133 In fact, in order for Mary to be able to give the free assent of her faith to the announcement of her vocation, it was necessary that she be wholly borne by God's grace.
491 Through the centuries the Church has become ever more aware that Mary, "full of grace" through God,134 was redeemed from the moment of her conception. That is what the dogma of the Immaculate Conception confesses, as Pope Pius IX proclaimed in 1854:
The most Blessed Virgin Mary was, from the first moment of her conception, by a singular grace and privilege of almighty God and by virtue of the merits of Jesus Christ, Savior of the human race, preserved immune from all stain of original sin.135
492 The "splendor of an entirely unique holiness" by which Mary is "enriched from the first instant of her conception" comes wholly from Christ: she is "redeemed, in a more exalted fashion, by reason of the merits of her Son."136 The Father blessed Mary more than any other created person "in Christ with every spiritual blessing in the heavenly places" and chose her "in Christ before the foundation of the world, to be holy and blameless before him in love."137
493 The Fathers of the Eastern tradition call the Mother of God "the All-Holy" (Panagia), and celebrate her as "free from any stain of sin, as though fashioned by the Holy Spirit and formed as a new creature."138 By the grace of God Mary remained free of every personal sin her whole life long.
494 At the announcement that she would give birth to "the Son of the Most High" without knowing man, by the power of the Holy Spirit, Mary responded with the obedience of faith, certain that "with God nothing will be impossible": "Behold, I am the handmaid of the Lord; let it be [done] to me according to your word."139 Thus, giving her consent to God's word, Mary becomes the mother of Jesus. Espousing the divine will for salvation wholeheartedly, without a single sin to restrain her, she gave herself entirely to the person and to the work of her Son; she did so in order to serve the mystery of redemption with him and dependent on him, by God's grace: 140
As St. Irenaeus says, "Being obedient she became the cause of salvation for herself and for the whole human race."141 Hence not a few of the early Fathers gladly assert …: "The knot of Eve's disobedience was untied by Mary's obedience: what the virgin Eve bound through her disbelief, Mary loosened by her faith."142 Comparing her with Eve, they call Mary "the Mother of the living" and frequently claim: "Death through Eve, life through Mary."143
495 Called in the Gospels "the mother of Jesus," Mary is acclaimed by Elizabeth, at the prompting of the Spirit and even before the birth of her son, as "the mother of my Lord."144 In fact, the One whom she conceived as man by the Holy Spirit, who truly became her Son according to the flesh, was none other than the Father's eternal Son, the second person of the Holy Trinity. Hence the Church confesses that Mary is truly "Mother of God" (Theotokos).145
496 From the first formulations of her faith, the Church has confessed that Jesus was conceived solely by the power of the Holy Spirit in the womb of the Virgin Mary, affirming also the corporeal aspect of this event: Jesus was conceived "by the Holy Spirit without human seed."146 The Fathers see in the virginal conception the sign that it truly was the Son of God who came in a humanity like our own. Thus St. Ignatius of Antioch at the beginning of the second century says:
You are firmly convinced about our Lord, who is truly of the race of David according to the flesh, Son of God according to the will and power of God, truly born of a virgin, … he was truly nailed to a tree for us in his flesh under Pontius Pilate … he truly suffered, as he is also truly risen.147
497 The Gospel accounts understand the virginal conception of Jesus as a divine work that surpasses all human understanding and possibility: 148 "That which is conceived in her is of the Holy Spirit," said the angel to Joseph about Mary his fiancee.149 The Church sees here the fulfillment of the divine promise given through the prophet Isaiah: "Behold, a virgin shall conceive and bear a son."150
498 People are sometimes troubled by the silence of St. Mark's Gospel and the New Testament Epistles about Jesus' virginal conception. Some might wonder if we were merely dealing with legends or theological constructs not claiming to be history. To this we must respond: Faith in the virginal conception of Jesus met with the lively opposition, mockery or incomprehension of non-believers, Jews and pagans alike; 151 so it could hardly have been motivated by pagan mythology or by some adaptation to the ideas of the age. The meaning of this event is accessible only to faith, which understands in it the "connection of these mysteries with one another"152 in the totality of Christ's mysteries, from his Incarnation to his Passover. St. Ignatius of Antioch already bears witness to this connection: "Mary's virginity and giving birth, and even the Lord's death escaped the notice of the prince of this world: these three mysteries worthy of proclamation were accomplished in God's silence."153
499 The deepening of faith in the virginal motherhood led the Church to confess Mary's real and perpetual virginity even in the act of giving birth to the Son of God made man.154 In fact, Christ's birth "did not diminish his mother's virginal integrity but sanctified it."155 And so the liturgy of the Church celebrates Mary as Aeiparthenos, the "Ever-virgin."156
500 Against this doctrine the objection is sometimes raised that the Bible mentions brothers and sisters of Jesus.157 The Church has always understood these passages as not referring to other children of the Virgin Mary. In fact James and Joseph, "brothers of Jesus," are the sons of another Mary, a disciple of Christ, whom St. Matthew significantly calls "the other Mary."158
They are close relations of Jesus, according to an Old Testament expression.159
501 Jesus is Mary's only son, but her spiritual motherhood extends to all men whom indeed he came to save: "The Son whom she brought forth is he whom God placed as the first-born among many brethren, that is, the faithful in whose generation and formation she co-operates with a mother's love."160
502 The eyes of faith can discover in the context of the whole of Revelation the mysterious reasons why God in his saving plan wanted his Son to be born of a virgin. These reasons touch both on the person of Christ and his redemptive mission, and on the welcome Mary gave that mission on behalf of all men.
503 Mary's virginity manifests God's absolute initiative in the Incarnation. Jesus has only God as Father. "He was never estranged from the Father because of the human nature which he assumed … He is naturally Son of the Father as to his divinity and naturally son of his mother as to his humanity, but properly Son of the Father in both natures."161
504 Jesus is conceived by the Holy Spirit in the Virgin Mary's womb because he is the New Adam, who inaugurates the new creation: "The first man was from the earth, a man of dust; the second man is from heaven."162 From his conception, Christ's humanity is filled with the Holy Spirit, for God "gives him the Spirit without measure."163 From "his fullness" as the head of redeemed humanity "we have all received, grace upon grace."164
505 By his virginal conception, Jesus, the New Adam, ushers in the new birth of children adopted in the Holy Spirit through faith. "How can this be?"165 Participation in the divine life arises "not of blood nor of the will of the flesh nor of the will of man, but of God."166 The acceptance of this life is virginal because it is entirely the Spirit's gift to man. The spousal character of the human vocation in relation to God167 is fulfilled perfectly in Mary's virginal motherhood.
506 Mary is a virgin because her virginity is the sign of her faith "unadulterated by any doubt," and of her undivided gift of herself to God's will.168 It is her faith that enables her to become the mother of the Savior: "Mary is more blessed because she embraces faith in Christ than because she conceives the flesh of Christ."169
507 At once virgin and mother, Mary is the symbol and the most perfect realization of the Church: "the Church indeed … by receiving the word of God in faith becomes herself a mother. By preaching and Baptism she brings forth sons, who are conceived by the Holy Spirit and born of God, to a new and immortal life. She herself is a virgin, who keeps in its entirety and purity the faith she pledged to her spouse."170
508 From among the descendants of Eve, God chose the Virgin Mary to be the mother of his Son. "Full of grace," Mary is "the most excellent fruit of redemption" (SC 103): from the first instant of her conception, she was totally preserved from the stain of original sin and she remained pure from all personal sin throughout her life.
509 Mary is truly "Mother of God" since she is the mother of the eternal Son of God made man, who is God himself.
510 Mary "remained a virgin in conceiving her Son, a virgin in giving birth to him, a virgin in carrying him, a virgin in nursing him at her breast, always a virgin" (St. Augustine, Serm. 186, 1: PL 38, 999): with her whole being she is "the handmaid of the Lord" (Lk 1:38).
511 The Virgin Mary "cooperated through free faith and obedience in human salvation" (LG 56). She uttered her yes "in the name of all human nature" (St. Thomas Aquinas, Sth III, 30, 1). By her obedience she became the new Eve, mother of the living.
963 Since the Virgin Mary's role in the mystery of Christ and the Spirit has been treated, it is fitting now to consider her place in the mystery of the Church. "The Virgin Mary … is acknowledged and honored as being truly the Mother of God and of the redeemer … . She is 'clearly the mother of the members of Christ' … since she has by her charity joined in bringing about the birth of believers in the Church, who are members of its head." 502 "Mary, Mother of Christ, Mother of the Church."503
964 Mary's role in the Church is inseparable from her union with Christ and flows directly from it. "This union of the mother with the Son in the work of salvation is made manifest from the time of Christ's virginal conception up to his death";504 it is made manifest above all at the hour of his Passion:
Thus the Blessed Virgin advanced in her pilgrimage of faith, and faithfully persevered in her union with her Son unto the cross. There she stood, in keeping with the divine plan, enduring with her only begotten Son the intensity of his suffering, joining herself with his sacrifice in her mother's heart, and lovingly consenting to the immolation of this victim, born of her: to be given, by the same Christ Jesus dying on the cross, as a mother to his disciple, with these words: "Woman, behold your son."505
965 After her Son's Ascension, Mary "aided the beginnings of the Church by her prayers."506 In her association with the apostles and several women, "we also see Mary by her prayers imploring the gift of the Spirit, who had already overshadowed her in the Annunciation."507
966 "Finally the Immaculate Virgin, preserved free from all stain of original sin, when the course of her earthly life was finished, was taken up body and soul into heavenly glory, and exalted by the Lord as Queen over all things, so that she might be the more fully conformed to her Son, the Lord of lords and conqueror of sin and death."508 The Assumption of the Blessed Virgin is a singular participation in her Son's Resurrection and an anticipation of the resurrection of other Christians:
In giving birth you kept your virginity; in your Dormition you did not leave the world, O Mother of God, but were joined to the source of Life. You conceived the living God and, by your prayers, will deliver our souls from death.509
967 By her complete adherence to the Father's will, to his Son's redemptive work, and to every prompting of the Holy Spirit, the Virgin Mary is the Church's model of faith and charity. Thus she is a "preeminent and … wholly unique member of the Church"; indeed, she is the "exemplary realization" (typus) 510 of the Church.
968 Her role in relation to the Church and to all humanity goes still further. "In a wholly singular way she cooperated by her obedience, faith, hope, and burning charity in the Savior's work of restoring supernatural life to souls. For this reason she is a mother to us in the order of grace."511
969 "This motherhood of Mary in the order of grace continues uninterruptedly from the consent which she loyally gave at the Annunciation and which she sustained without wavering beneath the cross, until the eternal fulfillment of all the elect. Taken up to heaven she did not lay aside this saving office but by her manifold intercession continues to bring us the gifts of eternal salvation … Therefore the Blessed Virgin is invoked in the Church under the titles of Advocate, Helper, Benefactress, and Mediatrix."512
970 "Mary's function as mother of men in no way obscures or diminishes this unique mediation of Christ, but rather shows its power. But the Blessed Virgin's salutary influence on men … flows forth from the superabundance of the merits of Christ, rests on his mediation, depends entirely on it, and draws all its power from it."513 "No creature could ever be counted along with the Incarnate Word and Redeemer; but just as the priesthood of Christ is shared in various ways both by his ministers and the faithful, and as the one goodness of God is radiated in different ways among his creatures, so also the unique mediation of the Redeemer does not exclude but rather gives rise to a manifold cooperation which is but a sharing in this one source."514
971 "All generations will call me blessed": "The Church's devotion to the Blessed Virgin is intrinsic to Christian worship."515 The Church rightly honors "the Blessed Virgin with special devotion. From the most ancient times the Blessed Virgin has been honored with the title of 'Mother of God,' to whose protection the faithful fly in all their dangers and needs …. This very special devotion … differs essentially from the adoration which is given to the incarnate Word and equally to the Father and the Holy Spirit, and greatly fosters this adoration."516 The liturgical feasts dedicated to the Mother of God and Marian prayer, such as the rosary, an "epitome of the whole Gospel," express this devotion to the Virgin Mary.517
972 After speaking of the Church, her origin, mission, and destiny, we can find no better way to conclude than by looking to Mary. In her we contemplate what the Church already is in her mystery on her own "pilgrimage of faith," and what she will be in the homeland at the end of her journey. There, "in the glory of the Most Holy and Undivided Trinity," "in the communion of all the saints,"518 the Church is awaited by the one she venerates as Mother of her Lord and as her own mother.
In the meantime the Mother of Jesus, in the glory which she possesses in body and soul in heaven, is the image and beginning of the Church as it is to be perfected in the world to come. Likewise she shines forth on earth until the day of the Lord shall come, a sign of certain hope and comfort to the pilgrim People of God.519
973 By pronouncing her "fiat" at the Annunciation and giving her consent to the Incarnation, Mary was already collaborating with the whole work her Son was to accomplish. She is mother wherever he is Savior and head of the Mystical Body.
974 The Most Blessed Virgin Mary, when the course of her earthly life was completed, was taken up body and soul into the glory of heaven, where she already shares in the glory of her Son's Resurrection, anticipating the resurrection of all members of his Body.
975 "We believe that the Holy Mother of God, the new Eve, Mother of the Church, continues in heaven to exercise her maternal role on behalf of the members of Christ" (Paul VI, CPG § 15).