The paper presents the concept of an “open work” (according to the idea of Umberto Eco) as a meaningfully undefined, and even non-finito work, which appeared in the artistic practice of the 20th century, at the time of revolutionary and military disasters. The events of the early 20th century in the social, psychological, and artistic consciousness of the leading avant-garde figures caused emotional and psychological shifts and contributed to the emergence of new ways of artistic expression. In art, works with different vector characteristics emerged: palimpsest, simulacrum, deconstruction, etc. Since then, the nature of general development of art became that of a rhizome. Similar principles of artistic thinking were predicted by H. Wölfflin in art (19th century) and in the aesthetics by A. Schopenhauer, F. Nietzsche, A. Bergson, and other philosophers of the early 20th century. The aesthetic concept of an “open work” and its special poetics reoriented the European art critics’ opinions regarding the analysis of modern artistic practice. Art studies focused on the artistic form in the very process of its formation (incompleteness). The process of forming an artistic work became the subject of meticulous analysis as something that is interesting to the modern viewer, who is a “synergistic person.” In the context of the poetics of an “open work,” the paper highlights the significance of the avant-garde discoveries of Oleksandr Arkhipenko as a pioneer of world modern sculpture. The connection of his philosophical and plastic thinking with dynamic social and scientific shifts in the life of mankind, with the “physics of space” of Albert Einstein, is visualized. The revolutionary role of caesuras (voids) in the volumes of Archipenko sculpture is defined. Under the angle of the concept of an “open work,” the article visualizes new forms of dialogue between modernists of the 21st century, in particular, Ukrainian artists and their recipients. The analysis of the works of modern Ukrainian artists (O. Zhyvotkov, O. Dzhuraeva, I. Grechanyk) illustrates the practical use of an “open form” as a modern practice in the time of psychological tension and uncertainty, in the state of stressful situations of the 2022–2024 war in Ukraine. “Staying before nothingness” (K. Jaspers’s expression), life on the threshold of existence caused irrationalism and “poetics of incompleteness” in the works of the mentioned artists. It was important to determine such a substantial characteristic of the work as ambiguity in its perception and reading. The paper reveals the psychological and plastic foundations of the authors’ artistic thinking when producing an “open work.” The productivity of a certain artistic paradigm is proven.