In the 1920s, the avant-garde group LEF advocated the "art of life construction" and proposed the "literature of fact," a distinct documentary literature. A notable critic opposing LEF was A. Voronsky, who believed in "art as the cognition of life". This report compares their contrasting views on the role of "knowledge" in art. Voronsky saw art as depicting the world's essence. According to him, writers must cultivate a pure, direct sense within themselves. For this, they need an infantile "ignorance" of the subject matter they depict. Voronsky's discussion of knowledge in art is a combination of V. Shklovsky's ostranenie and the ideas of philosopher, H. Bergson. The "literature of fact" starts by trying to overcome such infantile knowledge. S. Tretiakov discusses perspective in literary works based on his experience flying in a passenger plane. Tretiakov compares his first bird's-eye view of the country to a pair of unwiped glasses. According to Tretiakov, the world cannot be fully perceived without a detailed knowledge of the subject. For the avant-garde, who sought to incorporate human action into the cycle of material production, documentary literature about the production process was a means of involving people in it. LEF's emphasis on depicting knowledge of the production process was also a strategy to involve the reader in that very process.