Defining ideology as a system of functionally inter-connected political attitudes and beliefs, we review evidence concerning (1) the nature and origins of ideology in mass publics and (2) the social and interpersonal nature of the motives underlying ideological coherence. One key conclusion that we draw is that the links between psychological attributes and subsets of ideological attitudes sometimes appear to be organic and functional but other times appear to be conditional on how the relevant attitudes are packaged with other attitudes into socially constructed ideologies. A second key conclusion is that the social motives that induce citizens to pull diverse attitudes into ideological alignment may also, in polarized contexts, induce people to adopt non-political identities and self-perceptions that are congruent with ideological stereotypes. We recommend a focus on the implications of these processes for polarization and democratic stability.