This book is an attempt to proceed from earlier studies of art to a broader concern with visual perception as a cognitive activity a reversal, one might say, of the historical development that led in the philosophy of the eighteenth century from aisthesis to aesthetics, from sensory experience in general to the arts in particular. My earlier work had taught me that artistic activity is a form of reasoning, in which perceiving and thinking are indivisibly intertwined. A person who paints, writers, composes, dances, I felt compelled to say, thinks with his senses. This union of perception and thought turned out to be not merely a specially of the arts.