53 Faced with the poverty of the working class, Pope Leo XIII wrote: "We approach this subject with confidence, and in the exercise of the rights which manifestly pertain to us ... By keeping silence we would seem to neglect the duty incumbent on us". During the last hundred years the Church has repeatedly expressed her thinking, while closely following the continuing development of the social question. She has certainly not done this in order to recover former privileges or to impose her own vision. Her sole purpose has been care and responsibility for man, who has been entrusted to her by Christ himself: for this man, whom, as the Second Vatican Council recalls, is the only creature on earth which God willed for its own sake, and for which God has his plan, that is, a share in eternal salvation. We are not dealing here with man in the "abstract", but with the real, "concrete", "historical" man. We are dealing with each individual, since each one is included in the mystery of Redemption, and through this mystery Christ has united himself with each one for ever. It follows that the Church cannot abandon man, and that "this man is the primary route that the Church must travel in fulfilling her mission ... the way traced out by Christ himself, the way that leads invariably through the mystery of the Incarnation and the Redemption". This, and this alone, is the principle which inspires the Church's social doctrine. The Church has gradually developed that doctrine in a systematic way, above all in the century that has followed the date we are commemorating, precisely because the horizon of the Church's whole wealth of doctrine is man in his concrete reality as sinful and righteous.
Source: Centesimus Annus (Vatican.va)