The laity are gathered together in the People of God and make up the Body of Christ under one head. Whoever they are they are called upon, as living members, to expend all their energy for the growth of the Church and its continuous sanctification, since this very energy is a gift of the Creator and a blessing of the Redeemer.
We have a sacramental basis for the lay apostolate:
The lay apostolate, however, is a participation in the salvific mission of the Church itself. Through their baptism and confirmation all are commissioned to that apostolate by the Lord Himself. Moreover, by the sacraments, especially holy Eucharist, that charity toward God and (people) which is the soul of the apostolate is communicated and nourished. Now the laity are called in a special way to make the Church present and operative in those places and circumstances where only through them can it become the salt of the earth (Cfr. Pius XI, Litt. Encycl. Quadragesimo anno 15 maii 1931: AAS 23 (1931) p. 121 s. Pius XII, Alloc. De quelle consolation, 14 oct. 1951: AAS 43 (1951) p. 790 s.). Thus every lay(person), in virtue of the very gifts bestowed upon him (or her), is at the same time a witness and a living instrument of the mission of the Church itself “according to the measure of Christ’s bestowal”.(Eph. 4, 7.)
Not only is this apostolate a foundation for Christian activity in the world, but the laity have another endeavor in which to participate:
Besides this apostolate which certainly pertains to all Christians, the laity can also be called in various ways to a more direct form of cooperation in the apostolate of the Hierarchy (Cfr. Pius XII, Alloc. Six ans se sont ecoules, 5 oct. l9S7: AAS 49 (19S7) p. 927. De mandato et missione canonica, cfr. Decretum De Apostolatu laicorum, cap. IV, n. 16, cum notis 12 et 15.). This was the way certain men and women assisted Paul the Apostle in the Gospel, laboring much in the Lord.(Cf. Phil. 4, 3; Rom. 16, 3ff.) Further, they have the capacity to assume from the Hierarchy certain ecclesiastical functions, which are to be performed for a spiritual purpose.
Thus we have the modern reiteration for the foundation of lay ministry. The danger in recent trends to de-emphasize this is a potential danger to our brother priests, who have lost track, on occasion, of the “spiritual purpose” of ministry. We all face the danger of self-indulgence in these important endeavors of the spiritual life. Having two strong apostolates ready to assist each other is the best of possible situations for the Church.
Upon all the laity, therefore, rests the noble duty of working to extend the divine plan of salvation to all (people) of each epoch and in every land. Consequently, may every opportunity be given them so that, according to their abilities and the needs of the times, they may zealously participate in the saving work of the Church.