This thesis investigates the influence of political Catholicism and Catholic social doctrine on the evolution of the continental European welfare regimes. Paradoxically it finds that the doctrine had less influence on the formation of welfare regimes in countries where Catholicism was strong in contrast to countries where it was in a weak minority position. This finding does not only challenge many of the accounts that have perceived and analyzed religious influences on welfare state formation as a static and quantifiable variable but also addresses and rivals most postulations of mainstream welfare state theories such as Logic of Industrialism, Power Resource, Class Coalition and Employer Centered Approaches. In contrast to these postulations this thesis finds that welfare in continental Europe evolved during the 19th century and most of the 20th century as the result of a battle over ideas and worldviews between different societal groups and their political outlets. Which idea and worldview makes its way into institutional implementation is not primarily connected to the mere numerical strength or power resources of its societal and political representation but is a function of the performance of the programmatic ideas themselves. Decisive is how they strive in competition with other programmatic ideas. Two mechanisms stick out that determine whether programmatic ideas are successful: the performance and evolution of the idea in a process of ideational competition and the degree of ideational compatibility of a programmatic idea other ideas that enables the formation of ideational and political coalitions. The programmatic ideas and hence the worldview that performs these two tasks best wins its way into institutional implementation. Though, ideational competition, evolution and implementation is not solely endogenous to the battle of ideas but structured through a variety of exogenous factors such as the institutional (election system, mode of governance, degree of enfranchisement) and structural-material environment (pace of industrialization, spatial diffusion of economic development, number of ideational competitors). The thesis will show against the backdrop of the Italian and German welfare state development, from the end of the 19h century to the present, that these battles of ideas and worldviews were a major driver in how continental European political economies were structured during the 20th century.