In any given moment, concepts enable man to hold in the focus of his conscious
awareness much more than his purely perceptual capacity would permit. The range
of man’s perceptual awareness—the number of percepts he can deal with at any
one time—is limited. He may be able to visualize four or five units—as, for
instance, five trees. He cannot visualize a hundred trees or a distance of ten
light-years. It is only his conceptual faculty that makes it possible for him
to deal with knowledge of that kind.