Four Rules for Studying Populism examines why populism research remains conceptually unstable despite decades of definitional debate. It argues that the field’s dominant ideational, strategic, stylistic and Laclauian approaches construct different scientific objects under the same name because they rest on distinct and, in key respects, incompatible ontological commitments. The book offers the first systematic book-length examination of the consequences of treating these ontologically distinct objects as though they were competing or complementary accounts of a single phenomenon. Combining conceptual and historical reconstruction with a systematic analysis of 100 indexed journal articles and two extended examinations of theoretical synthesis, it shows how under-specification, proxy identification and conceptual slippage have become routine features of research practice. It formalises these problems through the Principle of Ontological Non-Synthesis and develops four rules for ontologically disciplined research: independent case constitution, ontology–evidence correspondence, controlled theoretical labour and ontology-indexed inference. The book ultimately advocates disciplined plurality and ontological parsimony: different objects may legitimately be studied under the name of populism, but researchers must respect the ontology of the framework they adopt, derive evidence from the object it constructs, and resist combining incompatible approaches unless they explicitly construct and defend a new theoretical object.

Manuel João Cruz holds a PhD in Communication Sciences from the University of Coimbra, with a thesis on populist narratives in the Portuguese Parliament. He is Assistant Professor at the University of Trás-os-Montes and Alto Douro and a postdoctoral researcher at the Centre for Social Studies, University of Coimbra, where he is part of the Democracy, Justice and Human Rights research group. His research focuses on populism, political communication, media, narrative, affect, and the instrumentalisation of trauma in politics. He was a researcher in the FCT-funded UNPOP project on populism, emotion narratives, and political behaviour, and currently collaborates on the Horizon Europe CO3 project. His work has appeared in Populism, Journal of Intercultural Studies, Politics and Governance, Social Sciences, and other outlets. He has also co-edited special issues on populism, emotions, minorities, and political communication, and developed open research resources on Portuguese parliamentary discourse.