SENSE-OBJECTS ARE UNREAL AND ARE CHIEFLY MADE UP OF APPEARANCE.
12. Plato[66] agreed with this, and being persuaded that, by participation, matter does not receive form and shape, as would some substrate that should constitute a composite of things intimately united by their transformation, their mixture, and their common affections; in order to demonstrate the opposite, namely, that matter remains impassible while receiving forms, invented a most apposite illustration of a participation that operates without anything being affected (namely, that engravers, before using dies on the soft wax, clean them carefully). Almost any other kind of illustration would fail to explain how the substrate can remain the same in the presence of forms. While trying to achieve his purpose, Plato has raised many questions; he has besides applied himself to demonstrate that sense-objects are devoid of reality, and that a large part of their hypostatic substance is constituted by appearance. Plato demonstrates the permanence and identity of matter by showing that it is by the figures with which it is endued that matter affects animated bodies, without itself suffering any of their affections. He wishes to convince us that in being endued with these figures, matter undergoes neither affection nor alteration. Indeed, in the bodies that successively assume different figures, we may, relying on analogy, call the change of figures an alteration; but since matter has neither figure nor existence,[67] how could we, even by analogy, call the presence of a figure an alteration? The only sure way of avoiding a misunderstanding in expression is to say that the substrate possesses nothing in the manner it is usually supposed to possess it. How then could it possess the things it contains, unless as a figure? Plato's illustration means that matter is impassible, and that it contains the apparent presence of images which are not really present therein.