What quality is shared by all objects that provoke our aesthetic emotions? Only one answer seems possible— significant form. In each, lines and colors combined in a particular way; certain forms and relations of forms, stir our aesthetic emotions. These relations and combinations of lines and colors, these aesthetically moving forms, I call 'Significant Form'; and 'Significant Form' is the one quality common to all works of visual art.

Art (ed. Perigee, 1958)