17 Various forms of the apostolate should be encouraged, and in the whole diocese or in any particular areas of it the coordination and close connection of all apostolic works should be fostered under the direction of the bishop. Thus all undertakings and organizations, be they catechetical, missionary, charitable, social, familial, educational, or anything else pursuing a pastoral aim, should be directed toward harmonious action. Thus at the same time the unity of the diocese will also be made more evident. The faithful should be earnestly urged to assume their duty of carrying on the apostolate, each according to his state in life and ability. They should be admonished to participate in and give aid to the various works of the apostolate of the laity, especially Catholic Action. Those associations should also be promoted and supported which either directly or indirectly pursue a supernatural objective, that is, either the attaining of a more perfect life, the spreading of the Gospel of Christ to all men, and the promoting of Christian doctrine or the increase of public worship, or the pursuing of social aims or the performing of works of piety and charity. The forms of the apostolate should be properly adapted to the needs of the present day with regard not only for man's spiritual and moral circumstances but also for his social, demographic, and economic conditions. Religious and social research, through offices of pastoral sociology, contributes much to the efficacious and fruitful attainment of that goal, and it is highly recommended.
Source: Christus Dominus (Vatican.va)