David Walter Hamlyn (1 October 1924 - 15 July 2012) was Professor of Philosophy at Birkbeck College, London (1964-1988), and editor of Mind (1972-1984). His major interests were in Aristotle (whose de Anima, II and III and parts of I, he translated with a commentary, 1968) and in Ludwig Wittgenstein, both of whom 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), was 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 was the history of philosophy.