1. In defining “apostolate,” Vatican II teaches that every member of the Church is called to share in it:
For this the Church was founded: that by spreading the kingdom of Christ everywhere for the glory of God the Father, she might bring all men to share in Christ’s saving redemption; and that through them the whole world might in actual fact be brought into relationship with him. All activity of the Mystical Body directed to the attainment of this goal is called the apostolate, and the Church carries it on in various ways through all her members. For by its very nature the Christian vocation is also a vocation to the apostolate. No part of the structure of a living body is merely passive but each has a share in the functions as well as in the life of the body. So, too, in the body of Christ, which is the Church, the whole body, “according to the functioning in due measure of each single part, derives its increase” (Eph 4.16). (AA 2)
This makes two things unmistakably clear. First, the apostolate includes the Church’s entire activity insofar as this is directed to extending redemption to all people. Second, every member of the Church has some share in the apostolate.
2. For a long time before Vatican II, there was uncertainty as to whether the apostolate includes only activities of a specifically religious character. If so, many thought that the apostolate would pertain primarily and properly to priests—indeed, only fully to bishops, as successors of the apostles—while the ordinary faithful would share in apostolic work only by helping priests and bishops. Vatican II clarifies this point.
3. The Church’s work of salvation “is done mainly through the ministry of the word and of the sacraments, which are entrusted in a special way to the clergy.” But the laity also have “their very important roles to play” in this ministry; “the apostolate of the laity and the pastoral ministry complement one another.” There are in fact “innumerable opportunities” available to the laity for carrying out “their apostolate of making the gospel known and men holy. The very testimony of their Christian life, and good works done in a supernatural spirit, have the power to draw men to belief and to God.” Good deeds, the Council further insists, must often be accompanied by the words of faith; to the extent of their ability and learning, the laity must explain, defend, and apply Christian principles (AA 6).
4. This suggests that here, as in other contexts, the revelatory activity which communicates divine truth and love is a complex of words and deeds (see DV 2). In the present instance, every Christian is called upon to reveal Jesus by a faithful life, whose significance is to be explained in terms of Christian truth.
5. Works of mercy toward persons and groups in great need are especially important if carried out in a really Jesus-like way (see AA 8). It would be a mistake, however, to limit the apostolate to specific types of acts. Works of mercy give especially effective witness to the love of God, but any good act which contributes to unfolding one’s Christian faith and love can be apostolic. Indeed, the content of the apostolate of the laity necessarily includes a wide range of secular activities: “The laity must take on the renewal of the temporal order as their own special obligation . . .. Outstanding among the works of this type of apostolate is that of Christian social action. This sacred Synod desires to see it extended now to the whole temporal sphere, including culture” (AA 7).
6. Hence, there can be no intrinsic limit to apostolate. The Council teaches that it “should reach out to all men wherever they can be found; it should not exclude any spiritual or temporal benefit” which one can confer. And it should take the form of the spoken word as well as deeds, since there are many people “who can hear the gospel and recognize Christ only through the laity who live near them” (AA 13).
7. The laity are not restricted to doing apostolic works in confraternities, Catholic action groups, and the like. In fact, “A particular form of the individual apostolate, as well as a sign especially suited to our times, is the testimony of a layman’s entire life as it develops out of faith, hope, and charity. This form manifests Christ living in those who believe in him. Then by the apostolate of the word, which is utterly necessary under certain circumstances, lay people announce Christ, explain and spread his teaching according to their situation and competence, and faithfully profess it” (AA 16; translation amended). It is an important part of this pervasive apostolate, the Council explains, to act always with motives which are visibly Christian. In this way, good acts have their greatest apostolic effectiveness.
8. While the Council is speaking of the laity in all these texts, most of what it says applies equally to every Christian’s life. More of course needs to be said in considering the specific form of the apostolate of the priest, who is ordained for the service of the word and the sacraments. The point here is simply that, if one understands what the apostolate is and how confirmation is a principle of Christian life, it follows necessarily that confirmation is the sacrament which assigns and strengthens Christians to live their entire lives as their share in the Church’s apostolate.
Vatican II does not explicitly say that confirmation is the sacrament of the apostolate, perhaps because “apostolate” is too easily understood in a narrower sense than the Council wishes, and perhaps because the sacrament of confirmation is to be conferred even on infants in danger of death, and in such conditions it seems irrelevant to apostolic activity.5
Nevertheless, confirmation consecrates the Christian for living and speaking as a witness to Jesus, and such witnessing precisely is the common essence of the apostolate. And Vatican II does say that the lay apostolate “. . . is a participation in the saving mission of the Church itself. Through their baptism and confirmation, all are commissioned to that apostolate by the Lord himself” (LG 33). Again, the Council teaches: “The laity derive the right and duty with respect to the apostolate from their union with Christ their Head. Incorporated into Christ’s Mystical Body through baptism and strengthened by the power of the Holy Spirit through confirmation, they are assigned to the apostolate by the Lord himself. They are consecrated into a royal priesthood and a holy people (cf. 1 Pt 2.4–10) in order that they may offer spiritual sacrifices through everything they do, and may witness to Christ throughout the world” (AA 3). These passages imply that confirmation is the sacrament of apostolate, although they stop short of saying this.
5. The Rites, 194 and 324.