This Summer Semester 1927 lecture course is an elaboration of the unpublished third division of the first part of Being and Time: Time and Being. The lecture course circles around the question of the meaning of being and consists of three parts.
In the introduction, Heidegger restates his claim that all ontology has an ontic fundament. He emphasizes that philosophy is grounded in human freedom. He also discusses the phenomenological method. It consists of three stages. Phenomenological reduction is the attempt to grasp entities in their being by returning to the self-manifestation of the phenomenon or the “things themselves.” The phenomenological construction is the projection of given entities with a view to their being and its structure, including being-there’s pre-ontological understanding of being. Phenomenological destruction is the critical dismantling of traditional concepts and points of view.
In the historical part of the course, Heidegger offers his students a destruction of four fundamental theses concerning being: (1) Immanuel Kant’s thesis that being is not a “real” predicate; (2) Aristotle’s thesis that to the being of entities belong essence and existence; (3) the thesis of René Descartes that being is either an extended or thinking substance; and (4) the logical thesis that the meaning of being is the copula or the “is.”
Heidegger tries to come to an understanding of time in the systematic part of the course. Through a careful interpretation of Aristotle’s vulgar concept of time, he shows how it presupposes the temporal and existential structure of being-there. In the next step, Heidegger develops the existential-horizonal character of temporality. This structure is the unity of awaiting, retaining, and making present. Temporality is the condition of possibility of the understanding of being. Heidegger regards the temporality (Zeitlichkeit) of existence as a kind of horizon whose outward expanse at once mirrors the temporality (Temporalität) of being. The temporal horizon forms the backdrop “in-terms-of-which” (das Woraufhin), and its meaning is disclosed in a way that permits its articulation in words. The grounding words are themselves temporal idioms, for example, “presencing,” that translate what is pre-understood concerning being into philosophical terms. At the close of the lecture, Heidegger reinvokes Kantian motifs to suggest that ontology is rooted in “temporal statements,” which express “temporal truth.” As a result, the ontology is a “temporal” and “transcendental” science which properly constitutes the science of being (Wissenschaft des Seins). Because the role that language plays in the thinking of being remains for the most part still to be clarified, this lecture course indicates Heidegger’s difficulty in formally “completing” Being and Time.