A pivotal thinker in this transformation is René Descartes (1596–1650 CE). In his Meditationes, after “proving” that the matter (res extensa) and mind (res cogitans) are different substances (i.e., forms of being existing independently), the question of the interaction between these substances becomes an issue. The malleability of wax is for Descartes an explicit argument against influence of the res extensa on the res cogitans (Meditationes II, 15). The fact that a piece of wax loses its form a