Mannheim also realized that the enlarged concept of ideology in Marxism raises a fundamental problem of knowledge. By denouncing something as "ideological," one takes an ideological position. Mannheim sees this as a spiritual and intellectual crisis in what is now a "Post-Marxist world". Our world is a polemical conflict between different worldviews, each labeling the other as "ideology." There are no criteria common to all with which to arbitrate the validity of one cultural perspective versus another. Even the class consciousness of the proletariat becomes one perspective among many.