The paper aims to show that Philoponus’ theory of sense-perception does not fit in with the spiritualist claim that the sensory process does not involve an extra material change in the sense-organ. Both the specific sense-organs (like the vitreous liquid and choroid or corneal membrane in the eyes) and the primary sense-organ (like the optic pneuma) contract or expand in the perceptual process. On the other hand, the literalist claim needs to be modified as well since only the tactile sense-organ (flesh) takes on the relevant qualities. Contraction or expansion in the sense-organ is triggered, not by physical changes in the medium, but by the formal activities arising from the perceptible objects: colours make the visual sense-organ contract or expand. At the level of sense-organs, the physiological process underlying sense-perception has three stages. The change in specific sense-organ will be transmitted to the primary sense-organ of the particular sense (optic/acoustic pneuma), and then reaches the common sense-organ, the pneuma. The primary sense-organs are spatially distinguishable parts of the common sense-organ which is otherwise homogeneous, not allowing for qualitative differences. The homogeneity of the pneuma establishes the unity of sense-perception at the level of physiological processes.
Aristotle’s notion of experience (in the sense involved in being an experienced person) occupies an important place in his account of scientific understanding and its methodology. It is linked, not only to sense-perception and the principles of skill and scientific understanding, but also, methodologically, to ἐπαγωγή. Due to its various involvements it has a complex job to perform. Such a complexity – or Janus-face – gives rise to many questions concerning its status and content. Many of these questions were raised in later antiquity. In the introductory part of the paper I shall give a very brief summary of Aristotle’s notion of experience, concentrating on issues that will be relevant next, and then discuss the explanation we find in a commentary which has come down to us under the name of Philoponus. I do it in the hope that the discussion sheds light on novelties in the commentator’s approach which deserve attention.