In many ways, mental imagery has been a fundamental issue in the history of philosophy. At least since Aristotle, philosophers have argued that knowledge is often represented in the form of mental images, taken to be inner pictures of some sort. However, questions have frequently been raised about the capacity of such images to play roles in thinking, remembering, and imagining; for instance, in George Berkeley's well-known doubts about the possibility of general or abstract images. Debates about mental imagery have been important in the history of psychology as well. Because the images in question are the bearers of conscious experience, claims about them have often been made on the basis of introspection, and the rejection of introspection in favor of behavioral studies was central to the emergence of psychology as a science. However, with the rise of cognitive science, quantified behavioral research has put mental...