BOOK I PART II
ent from what a blind man receives from his
eyes, or what is conveyed to us in the dark-
est night, it must partake of the same proper-
ties: And as blindness and darkness afford us
no ideas of extension, it is impossible that the
dark and undistinguishable distance betwixt
two bodies can ever produce that idea.
The sole difference betwixt an absolute dark-
ness and the appearance of two or more visible
luminous objects consists, as I said, in the ob-
jects themselves, and in the manner they affect
our senses. The angles, which the rays of light
flowing from them, form with each other; the
motion that is required in the eye, in its passage
from one to the other; and the different parts of
the organs, which are affected by them; these
produce the only perceptions, from which we
can judge of the distance. But as these percep-