La Vision chez Platon et Aristote

Neither Aristotle nor Plato content themselves with answering the question: How do we see?. In their examination of this scientific issue, they go further, and answer the more fundamental question: What is seeing? The first question pertains to scientific enquiry, which seeks to explain a phenomenon by describing its mechanism. Both Aristotle and Plato give an accurate account of the causes that produce visual sensation. Their accounts differ, but are quite similar with regard to their scientific relevance; they have quite the same capacities and the same failures in their explanation of vision, achieved by equally economical means. The other question - What is seeing? - transcends the mere intention of giving an account of a mechanism, and considers vision from the viewpoint of problems concerning the being of the seer, of what is seen, and of the world in which this process takes place; and it touches upon issues concerning ontology as well as ethics, epistemology and aesthetics, and even theology.

Plato's theory reveals its depth when we grasp that sensible vision is that of a divine soul that lives on earth as in exile. Through vision, this soul may seek to escape from its condition, and recover its genuine nature; for vision is the only sense by which we can reach the stars, which, for Plato, feature the same harmony as that of the soul when it was first formed by the demiurge. Yet vision can also plunge the soul further down into its exile. Hence, the Platonic conception of mirror images, which he defines as real bodies, resulting from the coalescence between two fires; they actually occur at the surface of the mirror, without there being any reflection in the modern sense of the term. In this way, Plato refuses to endorse the idea that the mirror image is mere indirect vision, or something virtual, thereby saving the image in the proper sense. Thus, through vision, the soul can encounter inferior realities, which drag it further and further way from the things that are genuine and true.
Aristotle's concerns are primary epistemological. His theory provides a guarantee of the truth and reliability of the sense of sight, whereas Plato's theory defined the vision of color as pure sensation, without there being any particular reality in the observed body itself. In Aristotle's theory, the act of vision becomes instantaneous, so that the vision of a color is strictly simultaneous with the state of the body in which the color is observed. This instantaneity is the condition by which, in the Aristotelian physical system, the oneness of time itself can be attained. Moreover, Aristotle's concept of light provides the basis for the immediate and authentic presence of the divine solar star in the midst of the place that is subject to generation and to corruption. Yet Aristotle's theory, as set forth in the De anima and the De sensu, so closely related to the problem of truth, was to prove helpless once the philosopher is forced to explain peculiar phenomena (such as the halo, or the rainbow), which Greek optics had already considered to be formed by visual reflection. Aristotle will then temporarily forget his own theory, and adopt precisely the one he had previously condemned.