The article analyzes the principle of practice, which is on of key principles of Marxism (Marxism-Leninism) that functions as a criterion of truth in epistemology, and a perspec­tive according to which the essence of a personality and of social phenomena is formed exclusively by the given social and economic reality (the vulgar sociocentrism). In fact, the principle of practice has been interpreted as a principle of the unity of theory and practice. The author claims that an inquiry into the features of practical implementation of this principle in terms of ideologized science reveals a paradox. The paradox has to do with the peripheral status received by that the principle of unity of theory and practice as a criterion of truth in totalitarian regimes and had little influence on decision making. Due to the so-called epistemic bubbles and/or echo-chamber effects, sociocentrism nur­tured the phenomenon of ideological science. This resulted in the long-lasting support for non-scientific concepts that promised significant practical results, but later proved fruit­less. This phenomenon is discussed on the material of the so-called “Michurin biology” developed by T.D. Lysenko. The author the reasons why the discipline developed by T.D. Lysenko remained “alive” for so long without any firm practical confirmation for several decades. It is argued that within the so-called ideological science, the scientific criterion of reproducibility of an experiment gets demoted to the periphery of the metho­dological consciousness.