How can the mind and body, if defined as separate entities, interact and form unified psychophysical selves? How is a relationship possible between "beings" independent and separated: psychē, sōma, natural composites (sunhola)? From a Cartesian point of view, the res cogitans is opposed to the res extensa. The res extensa is divisible, material, corporeal, extensive. The res cogitans is indivisible, immaterial, incorporeal, inextant. For Aristotle, if we read him back from a modern point of view, there seem to be phenomena that are, strictly speaking, 'mental' or 'psychic': aisthēsis, mnēmē, pathos, epithymia, phantasia, dianoia, nous. On the other hand, noses, legs, houses, looms can all be described as entities of the external world. What is the relationship between phenomena of the psychē and phenomena that appear to be extra-mental?