VARIOUS THEORIES OF PERSPECTIVE.
1. What is the cause that when distant visible objects seem smaller, and that, though separated by a great space, they seem to be close to each other, while if close, we see them in their true size, and their true distance? The cause of objects seeming smaller at a distance might be that light needs to be focussed near the eye, and to be accommodated to the size of the pupils[50]; that the greater the distance of the matter of the visible object, the more does its form seem to separate from it during its transit to the eyes; and that, as there is a form of quantity as well as of quality, it is the reason (or, form) of the latter which alone reaches the eye. On the other hand, (Epicurus) thinks that we feel magnitude only by the passage and the successive introduction of its parts, one by one; and that, consequently, magnitude must be brought within our reach, and near us, for us to determine its quantity.