15 Two further documents by Paul VI without any direct link to social doctrine — the Encyclical Humanae Vitae (25 July 1968) and the Apostolic Exhortation Evangelii Nuntiandi (8 December 1975) — are highly important for delineating the fully human meaning of the development that the Church proposes . It is therefore helpful to consider these texts too in relation to Populorum Progressio . The Encyclical Humanae Vitae emphasizes both the unitive and the procreative meaning of sexuality, thereby locating at the foundation of society the married couple, man and woman, who accept one another mutually, in distinction and in complementarity: a couple, therefore, that is open to life . This is not a question of purely individual morality: Humanae Vitae indicates the strong links between life ethics and social ethics , ushering in a new area of magisterial teaching that has gradually been articulated in a series of documents, most recently John Paul II's Encyclical Evangelium Vitae . The Church forcefully maintains this link between life ethics and social ethics, fully aware that “a society lacks solid foundations when, on the one hand, it asserts values such as the dignity of the person, justice and peace, but then, on the other hand, radically acts to the contrary by allowing or tolerating a variety of ways in which human life is devalued and violated, especially where it is weak or marginalized.” The Apostolic Exhortation Evangelii Nuntiandi , for its part, is very closely linked with development, given that, in Paul VI's words, “evangelization would not be complete if it did not take account of the unceasing interplay of the Gospel and of man's concrete life, both personal and social.” “Between evangelization and human advancement — development and liberation — there are in fact profound links” : on the basis of this insight, Paul VI clearly presented the relationship between the proclamation of Christ and the advancement of the individual in society. Testimony to Christ's charity, through works of justice, peace and development, is part and parcel of evangelization , because Jesus Christ, who loves us, is concerned with the whole person. These important teachings form the basis for the missionary aspect of the Church's social doctrine, which is an essential element of evangelization . The Church's social doctrine proclaims and bears witness to faith. It is an instrument and an indispensable setting for formation in faith.
Source: Caritas in Veritate (Vatican.va)