Although it is tempting to think that one's political convictions reflect independent and unbiased thinking, research increasingly suggests that ideologies reflect motivational processes. The present paper integrates system justification and shared reality theories to propose that ideologies may function as prepackaged units of interpretation that spread because of basic human motives to understand the world, avoid existential threat, and maintain valued interpersonal relationships. The authors review evidence suggesting that affiliative motives may influence ideological beliefs to align with the progressive or conservative views shared within a given relationship or group. At the same time, such motives may lead disproportionately to the adoption of system-justifying worldviews. Implications for the context dependence of ideological convictions, the role that shared reality may play in group conflicts, and the relational bases of revolutionary change are discussed.