This article considers the principles of philosophical thinking in Søren Kierke- gaard’s nonclassical aesthetics. Special attention is given to his radical critique of “false” and “impersonal” rationalism. This does not only mean the rejection of the tradi- tional principles of classical metaphysics which claims “universality” and “universal meaning.” Kierkegaard also bases his philosophy on individual human life, or, in other words, personal existence with its unique inner world. His critique is more profound than that by Arthur Schopenhauer. Kierkegaard develops his own philosophy of “exi- stential crisis,” opposing subjective will and internal changes to abstract thinking and external influences. Kierkegaard’s works initiate the critical or nonclassical stage in Western aesthetics. The main place in it is occupied by the idea of the disharmony of the world: its subjective reflection is “split” consciousness that has lost contact with the traditional concepts of harmony, humanism, goodness, beauty and philosophy of art. His philosophy of art is that of the internal personal world and of free choice. He opposes the famous motto of Cartesian rationalism cogito ergo sum, his own statement “I am here and think because I do exist here.” So the notion of existence becomes fun- damental for his philosophical reflection which is focused on the topics of personal existence, destiny and perspectives of being. Since personal becoming never stops, the ability to exist is treated as a great art. The aim of genuine philosophy is not a knowled- ge of the external world but an inquiry into the deepest problems of personal being and creativity; its greatest enigma is existence. Hence Kierkegaard gives a new subject and new tasks to aesthetics and philosophy of art. When treating the problems of individual human existence, Kierkegaard and other followers of nonclassical aesthetics relied on an understanding of being as non- substantial (personality is not something given but a totality of constantly emerging potentials) and at the same time subjectivized their ontological problems. Thus the stre- ngthening of subjectivist tendencies in the post-Hegelian philosophy of art reaches here culmination. “Subjective ontology,” or “ontology” in the narrow sense of the word, is that which we can call the “pontaneous ego:” It determines the unconscious functioning of human “existence” in a specific individual consciousness. The whole individual exi- stence is enclosed, as it were, in a subjective environment, but we cannot affirm that existence is subjective.