(There is an opinion that) the medium first receives and then transmits the affection, and impression. For instance, if some one stand in front of us, and directs his gaze at some color, he also sees it; but the color would not reach us unless the medium had experienced the affection. To this it may be answered that there is no necessity for the affections to be experienced by the medium, inasmuch as the affection is already experienced by the eye, whose function consists precisely in being affected by color; or at least, if the medium be affected, its affection differs from that of the eye. For instance, a reed interposed between the hand and the fish called the "torpedo," or "electric ray," does not feel the same numbness which it nevertheless communicates to the holding hand; still, the hand would not be affected with numbness unless the reed formed a communication between the fish and the hand.[165] However, the matter is not beyond discussion, for (even without any intermediary, if for instance) the fisher were in (direct contact) with the "ray" inside of the net, he would also feel the electric numbness. This communication therefore seems based on sympathetic affections. That, by virtue of its nature, one being can be sympathetically affected by some other being, does not necessarily imply that the medium, if different, shares that affection; at least (it is certain that) it is not affected in the same manner. In such a case, the organ destined to experience the affection experiences it far better when there is no medium, even when the medium itself is susceptible to some affection. NECESSITY OF A MEDIUM IN THE THEORIES OF VARIOUS PHILOSOPHERS. 2. If vision[166] presupposes the union of the "light of the eye,"[167] with the light interposed (between the eye) and the sense-object itself, the interposed medium is the light, and this medium is necessary, on this hypothesis. (On the theory of Aristotle) the colored substance produces a modification in the medium; but nothing here would hinder this modification from reaching the eye itself, even when there is no medium. For, in this case, the medium is necessarily modified before the eye is. (The Platonic philosophers) teach that vision operates by an effusion of the light of the eye. They have no need to postulate a medium, unless indeed they should fear that the ray of the eye should lose its way; but this ray is luminous, and the light travels in a straight line. (The Stoics) explain vision by the resistance experienced by the visual ray. They cannot do without a medium.[168] (The Atomists and) the believers in "images" (such as Epicurus), insist that these images move in emptiness, thereby implying the existence of a free space to avoid hindering the images. Consequently as they will be hindered in a direct ratio to the existence of a medium, this opinion does not run counter to our own hypothesis (that there is no medium).