David W. Hamlyn (born 1924) is a philosopher who has been Professor of Philosophy at Birkbeck College, London (1964-1988), and editor of Mind (1972-1984). Interests in Aristotle and (he translated De anima with commentary, 1968) and in Ludwig Wittgenstein have influenced Hamlyn's approach to questions in epistemology and philosophy of psychology. His central thesis, developed in Experience and the Growth of Understanding (1978), Perception, Learning and the Self (1983), and In and Out of the Black Box (1990), is that in order to be a knower a being must be active and seek to regulate its beliefs in accord with a norm of truth: this requires membership of a community, interaction with which involves emotional responses. In short, knowers are social, affective agents. The other main area of Hamlyn's writing is history of philosophy.