 This broad understanding of experience is evident, too, in medieval conceptions of the origin and scope of perceptual knowledge. With regard to the origins of such knowledge, later empiricists would focus almost exclusively on the five “exterior senses.” But medieval authors, following Avicenna (Ibn Sīnā; 980–1037), commonly list up to five “interior senses” (Bates 2010: 138–39) alongside the exterior ones. Aquinas reduces these to four: the common sense, the imagination, the vis aestimativa (or cogitativa), and the sense memory (Aquinas ST 1a 78.4). The work of these interior senses involves an active role in shaping our perceptions, even those of our physical environment. The mind, in other words, is not entirely passive, even at its basic levels of operation. The vis aestimativa, for instance, refers to the power that even non-rational creatures have of making judgements about what is dangerous or useful: it shapes our perceptions by adding an evaluative component. (There is something analogous here to James Gibson’s theory of “affordances”  [sect. 2.2].)