This paper examines Bernard Williams’ challenge to liberal universalists (liberals “who assume their morality is universally applicable to everyone”) to provide a theory of error: “a story about the subject matter of political morality and about past people’s situation which explains why those people got it wrong about the subject matter.” It develops a theory of error that appeals to socio-historical conditions of the past to explain their role in making (1) liberal values and reasons epistemically inaccessible, and (2) motivations (...) to live up to them unavailable. (shrink)