On Network Theory

Research on social networks has grown considerably in the last decade. However, there is a certain amount of confusion about network theory---for example, what it is, what is distinctive about it, and how to generate new theory. This paper attempts to remedy the situation by clarifying the fundamental concepts of the field (such as the network) and characterizing how network reasoning works. We start by considering the definition of network, noting some confusion caused by two different perspectives, which we refer to as realist and nominalist. We then analyze two well-known network theories, Granovetter's strength of weak ties theory [Granovetter, M. S. 1973. The strength of weak ties. Amer. J. Sociol. 78 (6) 1360--1380] and Burt's structural holes theory [Burt, R. S. 1992. Structural Holes: The Social Structure of Competition . Havard University Press, Cambridge, MA], to identify characteristic elements of network theorizing. We argue that both theories share an underlying theoretical model, which we label the network flow model, from which we derive additional implications. We also discuss network phenomena that do not appear to fit the flow model and discuss the possibility of a second fundamental model, which we call the bond model. We close with a discussion of the merits of model-based network theorizing for facilitating the generation of new theory, as well as a discussion of endogeneity in network theorizing.