It was out of an awareness of his mission as the Successor of Peter that Pope Leo XIII proposed to speak out, and Peter’s Successor today is moved by that same awareness. Like Pope Leo and the Popes before and after him, I take my inspiration from the Gospel image of "the scribe who has been trained for the kingdom of heaven", whom the Lord compares to "a householder who brings out of his treasure what is new and what is old" (Mt 13:52). The treasure is the great outpouring of the Church’s Tradition, which contains "what is old" — received and passed on from the very beginning — and which enables us to interpret the "new things" in the midst of which the life of the Church and the world unfolds.
Among the things which become "old" as a result of being incorporated into Tradition, and which offer opportunities and material for enriching both Tradition and the life of faith, there is the fruitful activity of many millions of people, who, spurred on by the social Magisterium, have sought to make that teaching the inspiration for their involvement in the world. Acting either as individuals or joined together in various groups, associations and organizations, these people represent a great movement for the defence of the human person and the safeguarding of human dignity. Amid changing historical circumstances, this movement has contributed to the building up of a more just society or at least to the curbing of injustice.
The present Encyclical seeks to show the fruitfulness of the principles enunciated by Leo XIII, which belong to the Church’s doctrinal patrimony and, as such, involve the exercise of her teaching authority. But pastoral solicitude also prompts me to propose an analysis of some events of recent history. It goes without saying that part of the responsibility of Pastors is to give careful consideration to current events in order to discern the new requirements of evangelization. However, such an analysis is not meant to pass definitive judgments since this does not fall per se within the Magisterium’s specific domain.