What is a case, and what is a case study?

Case study is a common methodology in the social sciences (management, psychology, science of education, political science, sociology). A lot of methodological papers have been dedicated to case study but, paradoxically, the question ‘‘what is a case?’’ has been less studied. Hence the fact that researchers conducting a case study are sometimes surprised by what they are experiencing. The paper deals with the problem: Why is a real case study more puzzling than expected, having read the literature on case study? We assume that the answer lies in a paradox: despite what is suggested by the double singular ‘‘case study’’, a case study requires a comparative approach. This paper addresses the three fundamental issues one must tackle when doing a case study: What is my case a case of? What is the stuff that my case is made of? What can my case do? (or what do cases do?).