LIGHT AS ACTUALIZATION IS THE BEING OF THE LUMINOUS BODY, AND IS INCORPOREAL.
Thus the light that emanates from bodies is the actualization of the luminous body which is active exteriorly. The light in the bodies whose original nature is such, is the formal being of the originally luminous body. When such a body has been mingled with matter, it produces color. The actualization alone does not suffice to give color; it produces only the hue, because the actualization is the property of a subject, and depends on it, so that nothing can be withdrawn from the subject without simultaneously being withdrawn from its actualization. Light is entirely incorporeal, though it be the actualization of a body. It could not therefore properly be said of light that it withdraws or is present. The true state of affairs is entirely different; for the light, so far as it is the actualization of the luminous body, is its very being. The image produced in a mirror is therefore an actualization of the visible object, which acts on anything that is passive (that can suffer, or experience), without letting any of its substance escape by any wastage. If the object be present, the image appears in the mirror; it is as it were the image of the color that possesses some particular figure. When the object withdraws, the diaphanous body no longer possesses what it possessed while the visible object was acting on the mirror. A similar condition is that of the soul; her actualization dwells within the (world's) body so long as this soul herself dwells within it.