The period between the French Revolution and the mid-twentieth century was a period of significant upheaval for Catholicism and in its interpretation of its role in relationship to the growth of nationalism, human rights and international relations. Chapter 1 examines how the Church developed Catholic social and political thought through human rights ideas. Catholicism gradually responded to the emergence of rights-based language, which it initially rejected, and only later engaged in active participation. Section 1.2 appraises in what manner the Catholic Church had available a long cosmopolitan tradition of reflection on the natural law, and this tradition in particular became a resource to a changing political landscape. Section 1.3 appraises the Catholics resolution of the tensions in rights language through the development of the philosophy of Personalism, and a reassessment of democracy as a foundation of cosmopolitan political life. This chapter concludes in Section 1.4 by presenting where those ideas were reaffirmed in later papal declarations and encyclicals.