Meyer Schapiro quotes:

Nature and abstract forms are both materials for art, and the choice of one or the other flows from historically changing interests.

Style is, above all, a system of forms with a quality and a meaningful expression through which the personality of the artist andthe broad outlook of a group are visible,... communicating and fixing certain values of religious, social, and moral life through the emotional suggestiveness of forms. It is, besides, a common ground against which innovations and individuality of particular works may be measured.

The movement of abstract art... bears within itself at almost every point the mark of the changing material and psychological conditions surrounding modern culture.