The present work is a defence of scientific materialism. It begins by arguing in the face of received criticism, that it does appear possible to define the theory such that it merits serious attention. The main obstacle foe the theory is then identified as the fact that our perceptual experience suggests that there are constituents in the world that it cannot allow - in particular, the unanalysable, indefinable qualia that characterise our experience of Secondary Qualities and sensations, and, also^ sensations located where there is no corresponding physical phenomenon. Two main approaches to the problems these items pose are identified. The first is the Analytical Approach, which claims that existing concepts relating to perceptual experience may be analysed so ns to avoid conflicts with materialism. Such analyses fail, however - notably because they cannot deal satisfactorily with the distinction between ordinary conscious perceptual experiences and unusual, and arguably unconscious, perceptual episodes, so favouring the second approach, that of Eliminative Materialism. An attempt is made, first, to present a coherent formulation of this defence in the light of recent discussion, and attention then focusses on its central tenet, that we may revise our beliefs about the content of perceptual experience to avoid conflict with materialism. The main reason for opposing the latter view is the idea that the beliefs concerned are indubitable, but then repeated attempts to vindicate their indubitability, based on a sufficiently strong understanding of this notion, are found here to fail. This enables a Kantian account of perceptual experience, finally, to be presented that is not only compatible with materialism, but also retains perceptual experience as a distinctly conscious occurrence, and explains why it should seem there are items in the world that materialism cannot allow, without entailing that any really exist.