This chapter focuses on a key debate in the philosophy of social science: whether it is possible to separate facts and values in social science research. It first considers normative and empirical theory in political research before discussing the ways in which the values of the researcher influence the research process. It then examines Thomas Kuhn’s arguments concerning paradigms and how they change through scientific ‘revolutions’, along with their implications for the possibility of value-free social inquiry. It looks at an example of how the notion of ‘paradigm’ has been applied to a specific area of inquiry within politics: the study of development. It also compares Kuhn’s paradigms with Imre Lakatos’ concept of ‘scientific research programmes’.