Abstract

Perception of the external world is an essential part of the animal (including human) life, both as a source of knowledge and as a way to survive. Medieval authors accepted this view, and despite general concerns about the reliability of the senses in the acquisition of certain and objective knowledge, they thought that for the most part our perceptual system gets things right when it comes to the perceptual features of things—but not always. Our article focuses on thirteenth- and fourteenth-century philosophical discussions of illusions and other types of perceptual errors. Reception of incorrect information, misjudgments concerning perceptual objects, the binding problem, and similar cases that explain perceptual errors will be analyzed. We discuss what might be called medieval Aristotelian/Avicennian theories of perception and the internal senses (drawing mainly from Albertus Magnus and Thomas Aquinas), as well as the so-called perspectivist accounts of perception, especially that by Alhacen. Finally, we take up a debate between Peter Auriol and his critics, which contains elements that can be seen as precursors of later skeptical worries. The concern here is that, just like in contemporary discussions leading to disjunctivism, the absence of a secure way to distinguish between veridical and non-veridical perception leads to a general worry about the reliability of our experience of the world.