There is a tendency in current philosophical thought to treat sensory experiences as a peculiar species of propositional attitude. Alan Millar argues against this view. While allowing that experiences may in some sense bear propositional content, he presents a view of sensory experiences as a species of psychological state. He applies the resulting analytical framework to a discussion of justified belief, dealing, firstly, with how beliefs may derive justification from other beliefs, and secondly, with how current sensory experiences may contribute to the justification of a person's beliefs. A key theme in his general approach is that justified belief results from the competent exercise of conceptual capacities, some of which involve an ability to respond appropriately to current experience. In working out this approach the author develops a view of concepts and their mastery, explores the role of groundless beliefs drawing on suggestions of Wittgenstein, illuminates aspects of the thought of Locke, Hume, Quine, and Goldman, and finally offers a response to a sophisticated variety of scepticism.