This book seeks to explain centralisation and decentralisation, which are conceptualised as having three dimensions: an institutional (polity), a functional (policy), and an actor- and process-oriented dimension (politics). In terms of theory, three separate approaches are combined: socio-cultural, political-ideological, and macro-structural. Empirically, the book compares decentralisation within the Swiss cantons as 26 independent units of observation. Cantonal decentralisation is first predicted cross-sectionally using linear regression models. Three significant independent variables emerge: political culture, area, and the strength of left-wing parties. Then, using process tracing, four cantons are studied over time to move from identifying correlation to establishing causation. Finally, causal inferences for (de)centralisation as such are drawn, urging future federal and territorial politics studies to a) reconceptualise decentralisation into three distinct but related dimensions and to b) bridge the theoretical gap between socio-cultural, structural and party-political approaches to achieve more valid and reliable explanations of territorial governance.