This chapter focuses on the relationship between the processes of secularisation and Catholic religious revival that have shaped Europe's transition to modernity. The chapter falls into two parts. The first explores the deepening tension between an anti-clerical European liberalism at the height of its powers and confidence and a revitalised Catholic Church determined to mobilise the masses of the faithful in support of its objectives. The second part of the chapter explores the dialectical relationship between secular (liberal, republican) and clerical forms of mobilisation. Secularising movements and initiatives, it argues, triggered waves of confessional mobilisation and vice versa. In this process of challenge and response the two processes evolved in tandem. The chapter closes with a reflection on the significance of this paradoxical intertwining of opposed phenomena for the shaping of modern Europe. Even the most cursory overview of the history of Catholicism in nineteenth-century continental Europe reveals an apparently contradictory state of affairs. On the one hand, church properties were seized and sold off; ecclesiastical privileges (fiscal, political, juridical) were removed or curtailed; clerical authorities came under pressure to retreat from their commanding positions in education and charitable provision; liberal, national, radical and socialist political discourses were marked by an uncompromisingly anti-clerical rhetoric and Masonic and free-thinking associational networks sprang up to combat the influence of church institutions and doctrine over human affairs.