The boundary of pure reason in Kant

Drawing borders on reason as a problem; that is, "what the human reason knows and cannot know", "how to reach the right information or where it should stop" is one of the basic issues of philosophy from past to present. The main aim that Immanuel Kant, one of the founding names of German philosophy, wants to achieve in his philosophy of criticism, is to determine the whole scope of pure reason, both with its boundaries and content, according to general principles. In his philosophy of criticism, Kant argued that metaphysical knowledge cannot be known by the methods of positive sciences, contrary to what classical metaphysicians did. According to Kant, if metaphysics is to be possible as a science, the human reason must determine what is to be known a priori, determine its principles on this basis, and agree to exclude from science what is outside the field in which these principles can be applied. In order for metaphysics to be a science, the scientific basis and framework of this activity of the reason that transcends experience must be clearly demonstrated. Therefore, in relation to the problem of what the human reason knows and cannot know, what needs to be addressed first is to determine what, how much and how the pure reason can know independently of experience. In this context, in his critique, Kant made distinctions between the phenomenal (area that can be experienced with sense data) and numenal (area that cannot be experienced with sense data) with the concepts of a priori (not given in experience)-a posteriori (given in experience). He claimed that it is possible to obtain knowledge of phenomena, but that it is not possible to obtain knowledge of noumena. Kant justified this claim that "how synthetic a priori judgments are possible?", which do not come from experience but expand our knowledge as if it were experience-object knowledge by trying to show the source, scope and boundaries of synthetic a priori judgments. This problem brings along various questions that "How is pure mathematics possible?", "How is pure natural science possible?" and "How is metaphysics possible as a science?" In this study, the problem of "what is the boundary of pure reason?" is investigated through Kant's philosophy of criticism. Kant's philosophy of criticism, which serves as a touchstone in the history of philosophy; in order to better understand the effects of the questions and answers posed to the history of philosophy on post-Kantian philosophy, has been examined in the context of the concepts of "criticism" and "boundary". The main purpose of the study; to identify and analyze the problem of "the boundary of pure reason" in Kant's philosophy of criticism by determining the boundaries he draws to knowledge with his thoughts about the use of reason independent of experience, which guides his criticisms of traditional metaphysics; is to reveal the "boundary of pure reason" based on the discussions. For this purpose, in this study, the situations, possibilities and conditions that form the basis of the theoretical activities of the reason in the philosophy of Kant within the boundaries drawn to the reason have been revealed; the problem that "how is metaphysics possible as a science?" has been systematically investigated with together the problematic of "how are synthetic a priori judgments possible in mathematics and natural sciences?" considering the main arguments of transcendental philosophy. This examination has shown that synthetic a priori knowledge in metaphysics, that is, knowledge that will allow metaphysics to be an objective science, exceeds the boundaries of pure reason in metaphysics.