Who theorized the social self?
Social identity theory
"Thus, social categorization is still conceived as a haphazardly floating 'independent variable' which strikes at random as the spirit moves it. No links are made or attempted, between the conditions determining its presence and mode of operation, and its outcomes in widely diffused commonalities of social behaviour. Why, when and how is social categorisation salient or not salient? What kind of shared constructions of social reality, mediated through social categorization, lead to a social climate in which large masses of people feel they are in long-term conflict with other masses? What, for example, are the psychological transitions from a stable to an unstable social system?" (Original emphasis, p. 188)[26]