 Bacon is next concerned with optical illusions, inverted images, magnification, vision of distant objects, the moon illusion, and such matters. He seeks in a rational and experimental manner to solve the puzzles found in Ptolemy, Alhacen, and others. Still, he is a child of his sources, which do not provide him with the more advanced data and mathematical method that arose only later, in the seventeenth century. But they do provide him with a functional qualitative geometry of the eye and vision based on the best Greek and Islamic science. Bacon is committed to an intromission theory of vision, though he combines it with an extramissionist theory that avoids the anthropomorphisms of earlier extramissionist theories. He uses the latter theory mainly to emphasize the active role of the eye in vision.