From Pope St. John Paul II’s Apostolic Exhortation Familiaris Consortio (1981):
The Church is certainly aware of the many complex problems which couples in many countries face today in their task of transmitting life in a responsible way. She also recognizes the serious problem of population growth in the form it has taken in many parts of the world and its moral implications.
However, she holds that consideration in depth of all the aspects of these problems offers a new and stronger confirmation of the importance of the authentic teaching on birth regulation reproposed in the Second Vatican Council and in the Encyclical Humanæ vitæ.
For this reason, together with the Synod Fathers I feel it is my duty to extend a pressing invitation to theologians, asking them to unite their efforts in order to collaborate with the hierarchical Magisterium and to commit themselves to the task of illustrating ever more clearly the biblical foundations, the ethical grounds and the personalistic reasons behind this doctrine. Thus it will be possible, in the context of an organic exposition, to render the teaching of the Church on this fundamental question truly accessible to all people of good will, fostering a daily more enlightened and profound understanding of it: in this way God’s plan will be ever more completely fulfilled for the salvation of humanity and for the glory of the Creator.
A united effort by theologians in this regard, inspired by a convinced adherence to the Magisterium, which is the one authentic guide for the People of God, is particularly urgent for reasons that include the close link between Catholic teaching on this matter and the view of the human person that the Church proposes: doubt or error in the field of marriage or the family involves obscuring to a serious extent the integral truth about the human person, in a cultural situation that is already so often confused and contradictory. In fulfillment of their specific role, theologians are called upon to provide enlightenment and a deeper understanding, and their contribution is of incomparable value and represents a unique and highly meritorious service to the family and humanity.
— Familiaris Consortio 31