The thesis that the mind cannot directly apprehend features of the physical world - what Reid calls the Way of Ideas - is a staple of Early Modern philosophical tradition. This commitment to the direct awareness of, and only of, mental representations unifies the otherwise divergentphilosophical systems of Rationalists and Empiricists. Thomas Reid battles against this thesis on many fronts, in particular over the nature of perception. Ryan Nichols lays the groundwork for Reid's theory of perception by developing Reid's unheralded argument against a representational theory of thought, which Nichols applies to his discussion of the intentionality of perceptual states and Reid's appeal to 'signs'. Reid's efforts to preserve commonsense epistemic commitments also lead him to adopt unique theories about our concepts of primary and secondary qualities, and about original and acquired perceptions. About the latter pair, Nichols argues that most perceptual beliefs depend for their justification upon inferences. The Way of Ideasholds that sensations are objects of awareness and that our senses are not robustly unified. Nichols develops Reid's counter-proposals by examining his discussion of the evolutionary purpose of sensations, and the nature of our awareness of sensations, as well as his intriguing affirmative answer toMolyneux's questions.Nichols brings to the writing of this book a consummate knowledge of Reid's texts, published and unpublished, and a keen appreciation for Reid's responses to his predecessors. He frequently reconstructs arguments in premise/conclusion form, thereby clarifying disputes that have frustrated previousReid scholarship. This clarification, his lively examples, and his plainspoken style make this book especially readable. Reid's theory of perception is by far the most important feature of Reid's philosophical system, and Nichols offers what will be, for a long time to come, the definitive analysisof this theory.