 The “foundation” of cognition at all levels is its passivity (LongAnima II.54). This is particularly clear for the five external senses, which have as their objects the material qualities of the external world. Color, for instance, the proper object of sight, is an elemental mixture on the surface of bodies (ParaParv I.10 {15}), which acts on an illuminated medium and then the organ of the eye, making its recipient at each stage be like the color itself. The general (although not perfect) reliability of the process—that a sense with respect to its proper sense object “does not err in regard to it for the most part” (LongAnima II.63)—is a product of the natural world’s causal regularity. Indeed, the passivity of the five senses is such that Ibn Rushd, when speaking most carefully, seems to treat these organs as themselves simply the corporeal media through which sensible qualities are conveyed to the one true principle of sensation, the common sense (al-ḥiss al-mushtarak). He writes, for instance, that “through the innermost of all the curtains of the eye, the common sense can perceive the form” (ParaParv I.19 {30}); here is where we pass from a purely corporeal stage to “the first of the spiritual stages” (ParaParv II.26 {42–3}). The lesson he draws from Aristotle’s notoriously obscure treatment of common sense (De anima 425b12ff) is that the principle of sensation is “one in number and multiple in extremities and organs,” like a point at the center of a circle (ParaAnima ¶260). Only here is perception both self-aware and capable of assimilating the objects of multiple sensory modalities. All subsequent cognition is dependent on the information collected at this stage. (See Black 2019 for the theory’s strict empiricism.)