Kom, 2022, vol. XI (1) : 35–50 UDC: 14 Хајдегер М. 101 DOI: 10.5937/kom2201035G Original scientifc paper Heidegger’s Understanding of Philosophy in Secondary Literature of His First, Second, and Third Periods of Thought Safer Grbić Philosophy Department at the Faculty of Humanities and Social Sciences, University of Zagreb, Republic of Croatia In this paper, aligning with the focus international researchers have ded- icated to Heidegger’s major works in order to contribute to the elucida- tion of his teachings, our intention is to establish a hypothesis grounded in Heidegger’s secondary literature spanning his frst, second, and third periods of thought. Tis will be accomplished through an examination of his speeches, presentations, lectures, correspondences, notes, interviews, and the like. Tus, the hypothesis of this paper is aimed at demonstrating that Heidegger’s body of work does not constitute a static and defnitive delineation of philosophy that commences and concludes in a prescribed manner: instead, it represents a contemplation of the concept of philoso- phy throughout his entire oeuvre, achieved by engaging in the discourse of philosophy, problematizing metaphysics, and scrutinizing ontology. In this vein, this essay delves into Heidegger’s understanding of the relationship between philosophy and metaphysics during his frst period of thought, his comprehension of the problem of metaphysics in his second period of thought, and his interpretation of the interplay between ontology and the- ology/teologics in his third period of thought. Te ultimate objective is to shed light on Heidegger’s methodology, which underpins both his initial phenomenology and subsequent thought: the method of posing questions. Specifcally, the act of questioning has led to a critique of the obscuring of the ontological diference between Sein and Dasein, a critique that delivers an essential disruption to philosophical thought. Consequently, this under- scores the necessity of establishing the foundations for the task of thinking. Keywords: philosophy, metaphysics, ontology, theology, teologics, thought, Heidegger Corresponding author: safergrbic@hotmail.com