Materialist theories of inspiration again diverge between purely internal and purely external sources. Karl Marx did not treat the subject directly, but the Marxist theory of art sees it as the expression of the friction between economic base and economic superstructural positions, or as an unaware dialog of competing ideologies, or as an exploitation of a "fissure" in the ruling class's ideology. Therefore, where there have been fully Marxist schools of art, such as Soviet Realism, the "inspired" painter or poet was also the most class-conscious painter or poet, and "formalism" was explicitly rejected as decadent (e.g. Sergei Eisenstein's late films condemned as "formalist error"). Outside of state-sponsored Marxist schools, Marxism has retained its emphasis on the class consciousness of the inspired painter or poet, but it has made room for what Frederic Jameson called a ""political unconscious"" that might be present in the artwork. However, in each of these cases, inspiration comes from the artist being particularly attuned to receive the signals from an external crisis.