problem; the development of a character in a novel from a state of
simplicity or innocence through storm and stress into maturity or ruin;
the evolution of a sentiment in a sonnet towards its final statement
in the last line or two; the melody, in its departure from the keynote,
its going forth and return; the career of a line.

As I have indicated before, each type of unity has its specific
emotional quality. The very word harmony which we use to denote the
first mode is itself connotative of a way of being affected, of being
moved emotionally. The mood of this mode is quiet, oneness, peace. We
feel as if we were closely and compactly put together. If now, within
the aesthetic whole, we emphasize the variety, we begin to lose the
mood of peace; tensions arise, until, in the case of contrast and
opposition, there is a feeling of conflict and division in the self;
yet without loss of unity, because, if the whole is aesthetic, each of
the opposing elements demands the other; hence there is balance between
them, and this also we not only know to be there, but feel there. The
characteristic mood of the evolutionary type of unity is equally
unique--either a sense of easy motion, when the process is unobstructed,
or excitement and breathlessness, when there is opposition.

The different types of unity are by no means exclusive of each other
and are usually found together in any complex work of art. Symmetry
usually involves a combination of harmony and balance. The symmetrical
halves of a Greek vase, for example, are harmonious in so far as their
size and shape are the same, yet balanced as being disposed in opposite
directions, right and left. Rhythm is temporal symmetry, and so also
represents a combination of harmony and balance. Static rhythm is only
apparent; for in every seeming case, the rhythm really pervades the
succession of acts of attention to the elements rather than the elements