s broad as the world." This stanza from
Lowell is but little suggestive to young readers:--

"Such earnest natures are the fiery pith,
The compact nucleus, round which systems grow!
Mass after mass becomes inspired therewith,
And whirls impregnate with the central glow."[14]

Yet when Columbus and Luther and Garrison are mentioned as
illustrations of the meaning, it becomes world-wide in its
application. Still in order to get at the thought, there is first the
need of the specific and the concrete; afterward we pass to the
general and the abstract.

As abstract ideas are harder to get hold of than concrete facts, so
exposition has difficulties greater than those found in narration and
description. It is not so hard to tell what belongs in a story; the
events are all distinct. Nor is it so difficult to know what to
include in a description; one can look and see. In exposition this is
not so. In most minds ideas do not have distinct limits; the edges
rather are indistinct. It is hard to tell where the idea stops. In
writing of "The Uses of Coal," it is easy to wander over an indistinct
boundary and to take a survey of "The Origin of Coal." Not only may
one include what unquestionably should be excluded, but there is no
definite guide to the arrangement of the materials, such as was found
in narration. There a sequence of time was an almost infallible rule;
here the writer must search carefully how to arrange hazy ideas in
some effective form. As discourse comes to deal more with general
ideas, the difficulties of writing increase; and the difficulties are
not due to any new principles of structure which must be introduced.
When one says that the material should be selected according to the
familiar law of Unity, he has given the guiding principle. Yet the
real difficulty is still before an author: it is to decide what stamp
to put upon such elusive matter as ideas. They cannot be kept long
enough in the twilight of consciousness to analyze them; and often
ideas that have been marked "accepted" have, upon reexamination, to be
"rejected." To examine ideas--the material used in this form of
discourse--so thoroughly that they may be accurately, definitely known
in their backward relation and their bearing upon what follows, this
is the seat of the difficulty in exposition.

Exposition may conveniently be classified into exposition of a term,
or definition; and exposition of a proposition, which is