How did Heidegger show that the ontological possibility of Dasein’s totality and authenticity becomes ontically concrete?

Martin Heidegger's exploration of the ontological dimensions of Dasein, or human existence, and its totality and authenticity is a central theme in his philosophical work, particularly in "Being and Time." Heidegger argues that the ontological possibility of Dasein's totality and authenticity becomes ontically concrete through an analysis of Dasein's everyday existence and its relation to time.

Ontologically, Dasein's totality refers to its potential for authentic existence, realizing its possibilities and becoming fully engaged with its existence. Authenticity, in Heidegger's terms, is the mode of existence where Dasein takes ownership of its being, confronting its own possibilities and choosing its own path. However, Heidegger acknowledges the challenge of concretely realizing these ontological possibilities in the midst of everyday existence.

Heidegger introduces the concept of "being-towards-death" to emphasize the ultimate possibility that shapes Dasein's authentic existence. By recognizing the finitude of life and the inevitability of death, Dasein is prompted to confront its own existence and make meaningful choices. Death serves as a key existential moment that reveals the urgency and authenticity of Dasein's possibilities.

The ontically concrete manifestation of Dasein's totality and authenticity is grounded in its temporal existence. Heidegger introduces the concept of "temporality" to underscore the interconnectedness of past, present, and future in the experience of Dasein. Authentic existence involves a temporal unfolding where Dasein projects itself towards its future possibilities, understanding its past, and actively engaging with the present.

Through anticipatory resoluteness, Dasein can actualize its ontological possibilities in ontic terms. This involves making authentic choices that align with its ownmost potentialities. The concrete realization of authenticity requires an active engagement with everyday situations, relationships, and responsibilities, shaping one's existence in a manner that reflects individual autonomy and self-awareness.

In essence, Heidegger shows that the ontological possibility of Dasein's totality and authenticity becomes ontically concrete through a profound understanding of temporality, the acknowledgment of mortality, and the active engagement with everyday existence. Authentic existence, for Heidegger, is not an abstract ideal but a lived reality that emerges through the dynamic interplay of Dasein's temporal being and its choices in the world.