2. Whenever two or more impressions or ideas have something in common
that is appreciable, they are in harmony, in the measure of what they
have in common. The harmony increases as the common element increases;
or the common elements. It diminishes in the measure of every
difference or contrast. By the Order of Harmony I mean some recurrence
or repetition, some correspondence or likeness. The likeness may be in
sounds or in sights, in muscular or other sense-impressions. It may lie
in sensations, in perceptions, in ideas, in systems of thought.