According to one mode of regarding those two classes of mental
action, which are called reason and imagination, the former may be
considered as mind contemplating the relations borne by one thought
to another, however produced; and the latter, as mind acting upon
those thoughts so as to colour them with its own light, and composing
from them, as from elements, other thoughts, each containing within
itself the principle of its own integrity. The one is the [word
in Greek], or the principle of synthesis, and has for its objects
those forms which are common to universal nature and existence
itself; the other is the [word in Greek], or principle of analysis,
and its action regards the relations of things, simply as relations;
considering thoughts, not in their integral unity, but as the
algebraical representations which conduct to certain general results.
Reason is the enumeration of quantities already known; imagination
is the perception of the value of those quantities, both separately
and as a whole. Reason respects the differences, and imagination
the similitudes of things. Reason is to the imagination as the
instrument to the agent, as the body to the spirit, as the shadow
to the substance.[...]
Poetry, in a general sense, may be defined to be 'the expression
of the imagination': and poetry is connate with the origin of man.
Man is an instrument over which a series of external and internal
impressions are driven, like the alternations of an ever-changing
wind over an Aeolian lyre, which move it by their motion to
ever-changing melody. But there is a principle within the human
being, and perhaps within all sentient beings, which acts otherwise
than in the lyre, and produces not melody alone, but harmony,
by an internal adjustment of the sounds or motions thus excited
to the impressions which excite them. It is as if the lyre could
accommodate its chords to the motions of that which strikes them,
in a determined proportion of sound; even as the musician can
accommodate his voice to the sound of the lyre.[...] Hence men, even in the infancy of society, observe a certain
order in their words and actions, distinct from that of the objects
and the impressions represented by them, all expression being
subject to the laws of that from which it proceeds.
[...]