 Prichard continued to work and to lecture on topics in epistemology, in particular perception. He gave lectures on Modern Philosophy (Descartes, Locke, Berkeley and Hume) every year for the first five years of his tenure of the White’s Professorship. Indeed he lectured as often on these topics as on moral philosophy. He wrote on the perception of movement and the apprehension of time. He said, characteristically, that ‘the hearing a sound – a sound having as such a duration – and in general what is called the perceiving anything which has a duration – is absolutely underivative and cannot be resolved into anything else’ (Knowledge and Perception ed. Ross, 48). I cannot resist quoting also a passage from a lecture on perception which was not published in Prichard’s lifetime, with the warning that Prichard was known to trail his coat in lectures, in the hope of generating lively discussion (ibid., 59–60). ‘For as soon as we compare our states or processes of seeing with one another or with other states or processes of perceiving we have to allow that we do not see bodies. For example, it is certain that if we see bodies we in some cases see a body move, but it is also certain that we cannot possibly ever see a body move; for in spite of what the followers of Einstein say, motion is, and is always really thought of as, absolute, relative motion being a contradiction in terms. (I should like, incidentally, but without any sense of shame, to offer this statement as a specimen of one of the few statements of things which we can really be said to know.) And, motion being absolute, when we are said to be seeing a body move, we cannot possibly be really doing so, since a stationary body would present precisely the same appearance to us, provided our body was moving in a certain way, so that in that case we should be seeing a body move although in fact it was stationary.’