Heidegger’s notion of Being-towards-death, the possibility of the impossibility of being, has left a profound mark on the reflections on death in contemporary Western philosophy. Heidegger is a decisive figure in the contemporary movement to turn philosophical thanatology on its head: on the one hand, by the methodology of radically separating, on principle, the analysis of death from the question about possible immortality (which it consigns to the ontical realm, beyond the scope of its investigation), and, on the other hand, by “interiorizing”, so to speak, death within the series of phenomena that make up life. His originality lies in having developed speculation on death at the ontological level, which he carefully distinguishes from the ontical approach used by his predecessors, Simmel and Scheler. Heidegger is not interested in the modalities of perishing and decease; instead he sets forth an interpretation in which death, that is, “authentic dying” [das eigentliche Sterben] constitutes Dasein [being-there, existence] in its essential “potentiality-for-Being” [Sein-können]. He deduces this interpretation from his ontology of temporality, which is characterized by the categories of end, possibility, and future.

I will not examine the historical development of Heideggerian thanatology, from his early writings to the final seminars; nor will I analyze his sources or the influences on his work. I will limit myself to his definition of death as the possibility of the impossibility of Being, as he developed it in Being and Time. To do this, I will introduce, first, the distinction between the ontical and the ontological levels; second, I will show that Heidegger maintains, along with Epicurus, that it is impossible to experience “my death” in the sense of “the state of death”. In the third place, I will describe how the philosopher of Freiburg affirms that one cannot know with certainty one’s “authentic dying” through an analysis of someone else’s death. Fourth, I will discuss the solution that he proposes for obtaining such certainty by referring to the notion of Being-towards-death. This notion is based on his ontology of temporality, which is characterized by the concepts of potentiality-for-Being (Sein-können), possibility (Möglichkeit), Being-ahead-of-itself (Sich-vorweg-sein), and Being-towards-the-end (Sein-zum-Ende). I will conclude with a critique of the proposed solution: I will ask, among other questions, whether Heidegger really succeeds in deducing Being-towards-death and the certainty of existential “dying”, which he posits as fundamental principles of the ego, from the sole basis of his ontology of temporality, without having recourse to a provincial (narrow) ontical analysis of death.