But still I could not fully understand the meaning of what my teacher had told me concerning “light” and “shade” and “perspective”; and I did not hesitate to put my difficulties before him.

Were I to give the Sphere’s explanation of these matters, succinct and clear though it was, it would be tedious to an inhabitant of Space, who knows these things already. Suffice it, that by his lucid statements, and by changing the position of objects and lights, and by allowing me to feel the several objects and even his own sacred person, he at last made all things clear to me, so that I could now readily distinguish between a Circle and a Sphere, a Plane Figure and a Solid.