On the visual power: why images do not converge to a point
The sense receives images on the eye's surface, since a mathematical point is indivisible
Leonardo reasons about the nature of the visual power (virtu visiva). If all the images that reach the eye converged into an angle, by definition they would meet at the mathematical point, which is indivisible; then everything in the universe would appear as one indivisible thing, with no space even between one star and another. Since experience shows all things separated by proportioned, intelligible spaces, the faculty in which their images are impressed must itself be divisible, receiving the images mirrored on the eye's surface and then judging them within. A further note holds that every surface of a transparent body, inside and out, can receive the images of its objects, while the body's interior only transmits them. A pen diagram of a luminous body radiating toward the eye sits at the lower right.
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Images cannot converge to an indivisible point
If all images converged in an angle they would meet at the indivisible mathematical point, and then all things seen would appear as one, with no space between star and star. Because experience shows things divided by measurable spaces, the visual power must be divisible, taking the images mirrored on the eye's surface and judging them within.
Transparent surfaces receive images; interiors only transmit
Every surface of a transparent body, within and without, is fit to receive the images of its objects. No interior part enclosed by those surfaces can receive or form an image; it only gives passage to the images of the surface.