A taboo is an "unthinkable" action, that is, even the thought of violating it triggers social punishment. Taboos are the social "thought police," discouraging individuals from considering certain type of actions. We consider a simple model in which taboos are part of the definition of one's identity. Deliberating over breaking the taboo adds the action to the individual’s choice set and provides information on possible private benefits but is costly because it contradicts one's identity. The strength of the taboo is endogenously determined by the number of individuals that obey it without any consideration of its violation. We model stable taboos and examine how they can change and disappear over time as a result of changes in the distribution of private benefits gained from its violation. We assume that individuals are heterogeneous with respect to their attitudes towards social punishment. We then analyze the relationship between social heterogeneity and the strength as well as effectiveness of taboos, i.e., are taboos stronger in homogenous or heterogeneous societies? We extend our analysis and examine societies in which individuals may choose among several identities, characterized by different taboos or varying strengths of taboos. Having such a choice defines an evolutionary process with respect to identity: Some identities disappear while others flourish. We examine the characterization and the conditions giving rise to a multi-identity society.
