This book is about Rational Choice Theory (RCT). To be more precise, it is mainly about 'technical parts' of that theory. RCT is a school of thought in contemporary social sciences: sociology, political science, ethics, social psychology, history, theory of international relations, etc. The most characteristic feature of RCT is an assumption that the individuals under investigation enjoy a special sort of rationality that drives them to maximise their utility. This assumption of rationality, jointly with some other assumptions, constitutes, in RCT, the basis for explanations and predictions. RCT borrowed its approach from neo-classical economics.