In Perception and the Internal Senses Juhana Toivanen advances a detailed philosophical reconstruction of Peter of John Olivi's (ca. 1248-98) conception of the cognitive psychology of the sensitive (i.e. animal) soul. Like most medieval philosophers, Olivi thought that higher animals and human beings have many psychological capacities in common. The book analyses these capacities by concentrating on Olivi's conception of the metaphysics of the soul, his theory of perception, and his views about the post-sensory cognitive power which medieval philosophers called the internal senses. Being the first monograph in English that concentrates on Olivi's philosophical psychology, Perception and the Internal Senses enables us to understand better medieval ideas concerning animal psychology and the human/animal boundary.