Harmony
Harmony, therefore, though a necessary principle in all art, does not push herself to the front as does Principality. She follows naturally, if allowed to.
The Must Be’s and May Be’s of Composition
Of the other principles, Consistency or breadth, Continuity and its complement, Contrast, associate themselves in greater or less degree with Principality and Harmony, which are the must be’s; while Repetition, Radiation, Curvature and Interchange are reckoned as the may be’s of composition.