A dynamic and multifunctional account of middle-range theories.

This article develops a novel account of middle-range theories for combining theoretical and empirical analysis in explanatory sociology. I first revisit Robert K. Merton's original ideas on middle-range theories and identify a tension between his developmental approach to middle-range theorizing that recognizes multiple functions of theories in sociological research and his static definition of the concept of middle-range theory that focuses only on empirical testing of theories. Drawing on Merton's ideas on theorizing and recent discussions on mechanism-based explanations, I argue that this tension can be resolved by decomposing a middle-range theory into three interrelated and evolving components that perform different functions in sociological research: (i) a conceptual framework about social phenomena that is a set of interrelated concepts that evolve in close connection with empirical analysis; (ii) a mechanism schema that is an abstract and incomplete description of a social mechanism; and (iii) a cluster of all mechanism-based explanations of social phenomena that are based on the particular mechanism schema. I show how these components develop over time and how they serve different functions in sociological theorizing and research. Finally, I illustrate these ideas by discussing Merton's theory of the Matthew effect in science and its more recent applications in sociology. © London School of Economics and Political Science 2018.