Over time, philosophers and historians of science have introduced different notions of 'ways of thinking'. This book presents, compares, and contrasts these different notions. It focuses primarily on Ian Hacking's idea of 'style of reasoning' in order to assess and develop it into a more systematic theory of scientific thought, arguing that Hacking's theory implies epistemic relativism. Luca Sciortino also discusses the implications of Hacking's ideas for the study of the problem of contingency and inevitability in the development of scientific knowledge