The substance, the contents, must
commend themselves to the understanding directly, of themselves; whilst
the beautiful form speaks to the imagination, and flatters it with an
appearance of freedom.

But even further limitations are necessary in this innocent subserviency
to the senses, which is only allowed in the form, without changing
anything in the substance. Great moderation must be always used, and
sometimes the end in view may be completely defeated according to the
kind of knowledge and degree of conviction aimed at in imparting our
views to others. There is a scientific knowledge, which is based on
clear conceptions and known principles; and a popular knowledge, which is
founded on feelings more or less developed. What may be very useful to
the latter is quite possibly adverse to the former.

When the object in view is to produce a strict conviction on principles,
it is not sufficient to present the truth only in respect to its contents
or subject; the test of the truth must at the same time be contained in
the manner of its presentation. But this can mean nothing else than that
not only the contents, but also the mode of stating them, must be
according to the laws of thought. They must be connected in the
presentation with the same strict logical sequence with which they are
chained together in the seasonings of the understanding; the stability of
the representation must guarantee that of the ideas. But the strict
necessity with which the understanding links together reasonings and
conclusions, is quite antagonistic to the freedom granted to imagination
in matters of knowledge. By its very nature, the imagination strives
after perceptions, that is, after complete and completely determinate
representations, and is indefatigably active to represent the universal
in one single case, to limit it in time and space, to make of every
conception an individual, and to give a body to abstractions. Moreover,
the imagination likes freedom in its combinations, and admits no other
law in them than the accidental connection with time and space; for this
is the only connection that remains to our representations, if we
separate from them in thought all that is conception, all that binds them
internally and substantially together. The understanding, following a
diametrically opposite course, only occupies itself with part
representations or conceptions, and its effort is directed to distinguish
features in the living unity