My purpose in this dissertation is to investigate the workings of the imagination. As I argue in Chapter One, such an investigation reveals that we cannot adequately account for the phenomenon of imagining without invoking mental imagery. I thus develop and defend an imagery-based account of the imagination, which I call the imagery model. ;Despite its intuitive appeal and a long philosophical history, the imagery model has nonetheless fallen into disfavor in contemporary discussions of the imagination. This is due, at (...) least in part, to a strong presumption against mental images that has developed in this century. Overcoming this presumption is the primary task of Chapter Two. In Chapter Three, I address a second motivation for the rejection of the imagery model, namely, that there seem to be some mental exercises which are clearly exercises of the imagination but yet which do not consist of imagery. By separating the imagery model from several controversial theses with which it has been associated, I show how the imagery model can protect itself from the threat of these counterexamples. ;Once these obstacles to the acceptance of the imagery model have been removed, the need remains to provide an explanation of the role that the image plays in imagining. As I suggest, although the image is not what is imagined, it is in virtue of the image that anything is imagined at all. More specifically, the image serves to capture the subject of the imagining. My discussion of this claim in Chapter Four is heavily influenced by recent work in the philosophy of language; in particular, I rely on many of the insights of the causal theory of reference developed by Saul Kripke and Keith Donnellan. ;Ultimately, having developed a picture of the workings of the imagination, I take up what I call the question of imaginability, namely, "What can we imagine?" The imagery model yields the obvious result that the imaginable is limited to the imageable. I explore the consequences of this result and, in particular, the consequences it has for the use of the imagination as an epistemological guide to modality. (shrink)