  His integrated optics model follows an Epicurean and Lucretian intromission view, that vision is a function of rays of light atoms or image-bearing atoms that are received by our internal apparatus for vision. The structure of this apparatus was of great concern to Gassendi and his early collaborator on naturalist projects, Peiresc. The premise of their work was that Kepler was largely correct in postulating an optical image that gathers many rays into a coherent representation in the eye, focused on the retina by the crystalline lens. What troubled Gassendi and Peiresc, however, was the notion that such an image as cast upon the retina would be inverted, leaving the problem of identifying how we see the world as right-side up. Seeking a physiological solution—as against any psychological capacity that rights the inverted image—they suggested that the retina itself acts as a mirror which rights the inverted image projected upon it.