Kandinsky opens with two quotes—by Paul Signac and Eugene Delacroix— suggesting the “deep relationship between the arts, and especially between music and painting” (27); these quotes foretell the more abstract, spiritual nature which Kandinsky believes art will assume in the future.

He then discusses in depth the relationship between color and form, the two constitutive elements of art. Form can exist by itself, without color. Color cannot exist by itself, except in the mind, but must be defined by “boundaries” that consist of various forms. Form influences color by giving it shape and boundaries, and color in turn influences form by individuating it and giving it “different spiritual values” (29).

Form has both an “outer” and an “inner meaning.” Form’s outer meaning is as the boundary or “separating line” between various colors; its inner meaning is the way in which it affects the human soul. These meanings mutually support each other: If the inner meaning is “fully expressed,” the outer aspect will also be coherent and well made. Kandinsky thus states the second “guiding principle” of the inner need: “Form-harmony” must correspond with a particular “vibration of the human soul” (29).

Kandinsky discusses how an artist may harmonize the material and the nonmaterial in painting.