Nick Zangwill has defined formalism in art as referring to those properties "that are determined solely by sensory or physical properties—so long as the physical properties in question are not relations to other things and other times." The philosopher and architect
Branko Mitrovic has defined formalism in art and architecture as "the doctrine that states that the aesthetic qualities of works of visual art derive from the visual and spatial properties." According to the observation that works of art can in general contain formal properties and nonformal properties, the philosopher Nick Zangwill has delineated three types of formalism encountered at the turn of the 21st century. First, Zangwill identifies
extreme formalists who think "that all works of art are purely formal works—where a work is purely formal if all its aesthetic properties are formal aesthetic properties," then he defines
anti-formalist thinkers as those who "think that no works of art have formal aesthetic properties." The third type which Zangwill identifies as representing the transition of the philosophy of aesthetics into the 21st century is that of
moderate formalism, where its principal exponents defend the principle "that all the aesthetic properties of works of art in a select class are formal, and second, that although many works of art outside that class have nonformal aesthetic properties, many of those works also have important formal aesthetic properties that must not be ignored." Here she introduces a broad concept of symbol, an opaque-productive symbol: one that is not transparent to preconceived or predetermined referents and meanings, but rather produces new ones. ==Uses in art history==