Providing a thorough defence of economics against behavioural imperialism and psychologism, Arkadiusz Sieroo argues that psychology should not play a significant role in economic theory. He focuses on the role of rationality in economics, the psychological theories of the business cycle, the debate surrounding the impact of capitalism on mental health, and anti-market sentiment. Sieroo analyses rationality in economics through four concepts: the individual, methodological, metaphysical and the empirical, and evaluates the differences between economics and psychology. Chapters consider issues which undermine the validity of psychological theories of the business cycle, investigate whether economic systems should be assessed in terms of their impact on happiness or psychological well-being, and explore the psychological factors of anti-market sentiment. Rationality, Psychology and Capitalism is a crucial resource for students and scholars in economics, particularly those interested in behavioral economics. It will also be of benefit to philosophy, methodology and psychology students, with its focus on the issues at the intersection of economics and psychology.