This Winter Semester 1927–28 lecture course focuses on the transcendental aesthetic and the first book of the transcendental analytic. It is a more precise and detailed section-by-section interpretation of Immanuel Kant’s text than the book Kant and the Problem of Metaphysics. Heidegger explains to the last detail the significance of each concept in terms of its content and also considers other parallel passages in Kant’s work.
In the introduction, The “Critique of Pure Reason” as Laying the Foundation for Metaphysics as Science, Heidegger determines the relation between positive science, ontology, and fundamental ontology. Each science has for its object a specific realm of entities. These objectifications of entities are made possible by being- there’s pre-ontological understanding of being. Heidegger exemplifies the formation of objectification by the genesis of the modern mathematical sciences. Such an objectification, as for example nature, needs to be established by ontology as an objectification of an entity in its being. The problem of the Critique of Pure Reason is that of the laying of the foundation of metaphysics as to the preconditions for the appearance of entities in conformity with human cognition as finite. All founding ontological knowledge is a knowledge of the preconditions of experience and is pure or apriori. Kant’s central question is how are synthetic apriori judgments possible? Laying the foundation of metaphysics as science is, for Kant, not only a laying of a foundation of ontology; it is at the same time a critique of pure reason as a delimitation of its possible knowledge apriori.
The greater part of the lecture course is a phenomenological interpretation of the Critique of Pure Reason. Heidegger would not get to an explicit interpretation of the schematism of the concepts of pure understanding (Verstand). He only dealt with it in principle. He shows that synthetic apriori knowledge is possible on the basis of the original synthetic unity of the productive power of imagination, which in turn is made possible by temporality. Temporality is the basic structure of being-there. Its existential constitution enables being-there to have an understanding of being, and develop a universal determination in order to articulate the meaning of being in words. The possibility of being-there to comport itself toward other entities and toward others is grounded in its temporality.
Heidegger concludes by drawing a parallel between Kant’s attempt to outline temporality as the horizon of finite transcendence and his own effort to delineate time as the condition for the possibility of understanding being. He then acknowledges that, when he re-read Kant’s Critique of Pure Reason against the backdrop of Edmund Husserl’s phenomenology, his eyes were “opened” to a future direction of philosophy.