David Byrne is Emeritus Professor of Sociology and Applied Social Science at Durham University, UK. His research interests include complexity theory, post-industrial social structures, urban systems, taxation policy, the privatization of welfare systems, quantitative methods, and case-based methods. He is the author of Applying Social Science: The Role of Social Research in Politics, Policy and Practice (Policy Press, 2011), Class after Industry (Palgrave Macmillan, 2018)and Inequality in a Context of Climate Crisis after COVID: A Complex Realist Approach (Routledge, 2021) and co-author of Complexity Theory and the Social Sciences: The State of the Art (First Edition, Routledge, 2013) and Paying for the Welfare State in the 21st Century (Policy Press, 2017).

Gillian Callaghan is a teacher of social theory and qualitative methods and an experienced evaluator of social and health interventions. Her research interests include complexity theory, deindustrialization and post-industrial social structure, class, social capital and community, and issues of power, participation, and governance. She is the author of numerous journal articles and co-author of Complexity Theory and the Social Sciences: The State of the Art (First Edition, Routledge, 2013).

Introduction, 1. A manifesto for interdisciplinarity founded on the complexity frame of reference, 2. The complexity frame of reference and action, 3. Doing complexity science, 4. Evolutionary social theory, 5. Structure and agency, 6. Time and place, 7. Social theory and macro system transformation, 8. Complexity theory and the qualitative research programme, 9. Quantitative methods for exploring, understanding, and possibly predicting complex social systems and their intersection with natural systems, 10. Complexity and mixed methods, 11. Modes of governance, 12. Evaluation in a complexity frame, 13. Explicit complexity evaluation, 14. Shaping research and policy, 15. Beyond disciplines and fields: COVID and a world in crisis, Conclusion