Kant’s Thesis “Being Is Not a Real Predicate” Interpreted by Heidegger

The focus of this article is an interpretation of the key Kantian thesis, “being is not a real predicate”, advanced by Heidegger in his lecture course, The Basic Problems of Phenomenology (1927) wherein it is presented as one of the four fundamental theses on ‘being’ in the history of philosophy. The article describes the historical-philosophical context for Kant’s critique of the ontological proof of the existence of God. This critique is based on three interconnected components: logical, epistemological, and ontological. Next, it describes the specificities of the Kantian conceptual apparatus, with a detailed analysis of concepts key to understanding Kant’s thesis — ‘reality’, ‘real predicate’, and ‘being’ — and explains the relation of these concepts to the Kantian categories. I submit that Heidegger is interested not so much in the content of the Kantian critique of the ontological argument as in Kant’s interpretation of the concepts of ‘being’ and ‘existence’, which are central to the development of a fundamental ontology. Heidegger reduces the opaqueness of these concepts to the problem of the definition of the concept of ‘perception’; and, challenging Kant’s identification of existence with ‘perception’, argues that existence cannot be identical either to the act of perception, or to the perceived object, nor to its ‘perceivedness’ (Wahrgenommenheit). Heidegger accuses Kant of a lack of clarity, and of a positive definition of the concept of ‘existence’ — which, however, does not undermine the relevance of Kant’s thesis as a starting point for his own fundamental ontology. I demonstrate that, in spite of its shortcomings, Heidegger sees the Kantian thesis as a solid foundation upon which to pursue further the project of building ontology as phenomenology. This, however, calls for a more solid grounding and clarification of the horizon within which the question of ‘being’ is raised.