This book offers a multi-dimensional account of why the third sector (associations, foundations, cooperatives, social enterprises and related non-profit organizations) differs so markedly across European countries. Combining historical-institutional, political-economic, moral-cultural, legal-regulatory and structural-economic perspectives, it links values, cleavage histories, welfare-state design and institutionalized state&civil-society relations to observable national patterns of third-sector structure, function and behaviour. The volume pairs conceptual innovation with an original empirical programme (cluster analysis, multi-level modelling and policy-field case comparisons) and shows how different "third-sector regimes" arise from interactions between welfare institutions, moral logics, and economic contexts. It will be of interest to scholars and policy makers who want theory-driven, evidence-based explanations of cross-national variation in non-profit size, welfare provision by third-sector actors, organizational hybridity and the democratic role of civil society.