Even-Zohar substitutes univalent causal parameters with polyvalent factors as an instrument for explaining the complexity of culture within a single community and between communities. His "polysystem theory" analyzed sets of relations in literature and language, but gradually shifted towards a more complex analysis of socio-cultural systems. Even-Zohar’s polysystem theory has been embraced by students of literature and culture all over the world. The theory has proven particularly relevant in Spain and China.