16 In Populorum Progressio , Paul VI taught that progress, in its origin and essence, is first and foremost a vocation : “in the design of God, every man is called upon to develop and fulfil himself, for every life is a vocation.” This is what gives legitimacy to the Church's involvement in the whole question of development. If development were concerned with merely technical aspects of human life, and not with the meaning of man's pilgrimage through history in company with his fellow human beings, nor with identifying the goal of that journey, then the Church would not be entitled to speak on it. Paul VI, like Leo XIII before him in Rerum Novarum , knew that he was carrying out a duty proper to his office by shedding the light of the Gospel on the social questions of his time . To regard development as a vocation is to recognize, on the one hand, that it derives from a transcendent call, and on the other hand that it is incapable, on its own, of supplying its ultimate meaning. Not without reason the word “vocation” is also found in another passage of the Encyclical, where we read: “There is no true humanism but that which is open to the Absolute, and is conscious of a vocation which gives human life its true meaning.” This vision of development is at the heart of Populorum Progressio , and it lies behind all Paul VI's reflections on freedom, on truth and on charity in development. It is also the principal reason why that Encyclical is still timely in our day.
Source: Caritas in Veritate (Vatican.va)