Reflections on the contrast between the titles of Popper’s Objective Knowledge and Polanyi’s Personal Knowledge led Haack to explore how Polanyi’s ideas might be used to correct some of the distortions caused by Popper’s refusal to allow any role in epistemology to the knowing subject, and thus to throw light on such questions as the relations between the knower and the known, between epistemology and psychology and sociology of knowledge, and between subjectivity and objectivity.