The sun appears to be poured down, and in all directions indeed it is diffused, yet it is not effused. For this diffusion is extension: Accordingly its rays are called Extensions [aktines] because they are extended [apo tou ekteinesthai]. But one may judge what kind of a thing a ray is, if he looks at the sun's light passing through a narrow opening into a darkened room, for it is extended in a right line, and as it were is divided when it meets with any solid body which stands in the way and intercepts the air beyond; but there the light remains fixed and does not glide or fall off. Such then ought to be the out-pouring and diffusion of the understanding, and it should in no way be an effusion, but an extension, and it should make no violent or impetuous collision with the obstacles which are in its way; nor yet fall down, but be fixed and enlighten that which receives it. For a body will deprive itself of the illumination, if it does not admit it.