Introduction. The article is devoted to methodological issues of the formation of the worldview of universalism, excluding the reduction of the one, the whole, many and a part to each other. Limited, one-sided types of worldviews of holism, merism and the genological type allow such a reduction, excluding the choice of optimal, sustainable co-development of nature, society and a man. Theoretical analysis. A comparative analysis of the ideological and methodological attitudes of holism, merism and onecentrism is carried out in order to identify their reductionist extremes. As their replacement, the author proposes a new version of the worldview of universalism (postholism), formed by methodological means that exclude the absolutization of a one, whole or parts. The main means of such kind are the concept of a «one whole in a single part», the procedure of «harmonic convergence» and the principle of «non-reductionism», which ensure a tendency to fusion of the semantic content of the concepts of a one, whole, singular, and unique. Conclusion. The conclusion is made that, thanks to these tools, the worldview of postholism is able to neutralize the methodological flaws of holism, mechanicism, elementarism, individualism, henotheism, and other ideological and methodological platforms. This allows for a proportionate interaction in the course of the development of a one (fundamental laws of being), a whole (society) and a part (person).