“This is a wonderfully rich and provocative study of a central theme in eighteenth-century British though. Yolton’s knowledge of the original sources is phenomenal. He not only has fresh things to say about the familiar great works of the period -- Locke’s Essay and Hume’s Treatise especially -- but he also provides vivid accounts of a host of writings by less well-known authors. this book is bound to have a large impact on scholarship in the field of eighteenth-century studies. It should stimulate philosophers too, for many of whom the whole question of ‘thinking matter’ is still very much a live research issue.” --Vere Chappell, University of Massachusetts