Ad Reinhardt is an artist who shaped the American art market in the 1950s and 1960s both with his writings and his paintings. Reinhardt studied black paintings, which are all in the same format between 1960-66, by linking philosophies such as Neo-Platonism and Zen Buddhism to the East-West tradition of pure painting. For Reinhardt, the traditional texts of Buddhism, Hinduism, and Christian mysticism were intellectually intriguing sources that provided a rich basis for the increasingly complex and difficult to understand structure of black paintings. What fascinates Reinhardt about Zen and some mystical fields is that they relate to the concepts of meaninglessness and emptiness, and that they meet the artist's need for telling the abstract in a different way. The artist, who rejects the understanding of making a mimetic painting by moving the picture beyond being visible, defines his work as a logical development of his personal art. The aim of this study is to determine his subjectivity in the art of the 20th century by revealing the formal and conceptual foundations of black square paintings produced by Reinhardt. In the study, which was prepared based on literature review, the black square paintings produced by the artist between 1960 and 66, which are all in the same format, were examined formally and conceptually, and his understanding of art was evaluated and the evaluation was supported by his own discourses and related resources. The data were obtained from online magazines, books and newspapers in addition to the printed sources obtained from local and foreign literature. In the first part of the article, the early works of the artist are addressed and the factors that pave the way for the formation of black square paintings are discussed. In the second part, the process of making these paintings is discussed and analyzed technically and formally. In the last part, the reasons of the viewer's mutual dialogue with the work, the perception of the paintings and its being considered as the slow art are discussed conceptually. According to the findings, it was understood that there was a need for a slowdown similar to the eastern art and meditations that Reinhardt was philosophical and literary influenced in perception of his black format paintings, which he started in the 1960s. In order to establish the relationship between the work and the viewer, it was seen that the viewer needed more time, patience and focus than the time allocated to any work. Therefore, it is determined that the works of the artist, who aimed to create changes in the perception of the viewer with this conceptual experience called slow art, show resistance to instant consumption.