Social psychology has documented many surprising features of the human mind, providing robust evidence that people deceive themselves, are systematically overconfident, believe implausible things to avoid inconsistency, and so on. Explanations often focus on proximate psychological mechanisms (e.g., we avoid inconsistency because we find it uncomfortable). But behind every proximate mechanism is an ultimate explanation (why is inconsistency uncomfortable?)—why did evolution or learning lead us to be this way? This course will examine proximate and ultimate explanations for classic social psychological phenomena and the insight that ultimate level explanations add, with a focus on how to test ultimate explanations convincingly.