What Can the World Church Learn From the "World" - and Vice-Versa. It has sometimes been overlooked that Gaudium et spes sees the Church and the modern world engaged in a mutual learning process (GS 44). The relationship is thus not a one-way street. In this presentation I want to show that the hermeneutics of recognition of Vatican II initiated a new outlook on the social and political structures which thereafter became the backbone of Catholic Social Teaching (CST) and which has been promoted rather successfully in the World Church (human dignity, equality, solidarity, subsidiarity, human rights, participation and democracy). The full story of this sui generis inculturation of Catholicism into modernity has still to be told. Two fundamental questions pose themselves today. First: Can CST, which up to now has been at the margins of the Synodal Process, be a resource for the reform of ecclesial structures? Second, and of no lesser relevance in view of increasing trends of political autocratization and nationalism: How can the promotion of the principles of CST by the World Church continue to make a difference?