Typecasting, legitimation, and form emergence: a formal theory.

We propose a formal theory of multiple category memberships. This theory has the potential to unify two seemingly unconnected theories: typecasting and identity-based form emergence. Typecasting, a producer-level theory, considers the consequences of specializing versus spanning across category boundaries. Identity-based form emergence considers the evolution of categories and how the attributes of producers entering a category shape its likelihood of gaining legitimacy among relevant audiences. Both theory fragments treat the processes by which audience members assign category memberships to producers. This article develops this common foundation and outlines the arguments that lead to central implications of each theory. The arguments are formalized using modal expressions to represent key categorization processes according to the theory-building framework developed by Hannan et al. (2007).