5 The declaration of these policies is not, in fact, an easy matter. All such policies must be derived first of all from an earnest consideration of divine doctrine, for even Christ Himself, we must remember, said: "My doctrine is not mine, but his who sent me." (1) Then they must be shown to measure up to the present state of the Church, a state in which the Church's interior life is still vigorous, having stood the test of long experience, and its exterior energies are powerfully directed toward the work of the apostolate. And finally We must bear in mind the actual situation in which human society today finds itself. Our task is to serve society.
Source: Ecclesiam Suam (Vatican.va)