Book: Being and Time

Overview
Being and Time (1927) pursues the question of "being" by examining the specific mode of existence that humans have. Heidegger argues that traditional metaphysics has forgotten the meaning of Being and that renewed understanding requires an existential and phenomenological analysis of human existence, which he calls Dasein. The work aims to show that the structure of human existence makes possible any understanding of beings and of Being itself.
The book is organized into two major divisions. The first delivers an existential analytic of Dasein; the second was intended to address temporality and history as the ontological ground for a fuller account, but several planned sections remained unfinished at publication.

Method and Aim
Heidegger adopts a hermeneutic phenomenology that looks at how Being shows itself through everyday experience rather than through abstract theorizing. Phenomenology here is not merely description but an interpretive disclosure of structures that make understanding possible.
A key methodological move is the "ontological difference": the distinction between beings (entities) and Being (the condition of their intelligibility). Heidegger insists that asking about Being requires turning from specific entities to the concrete existential situation in which understanding arises.

Dasein and Being-in-the-World
Dasein, literally "being-there," designates the human way of existing characterized by care, concern, and an always-already situatedness. Dasein's primary mode is Being-in-the-world, a unitary condition in which subject and world are not separate but mutually implicated.
Heidegger distinguishes readiness-to-hand (Zuhandenheit) and presence-at-hand (Vorhandenheit) to describe how tools and objects appear. Most of the time things are encountered in a background of practical absorption rather than as theoretical objects, and this practical relation discloses a more fundamental kind of being.

Care, Thrownness, and Projection
Care (Sorge) is the existential structure that unites Dasein's temporal and practical dimensions: one is always already thrown into a world (Geworfenheit) and simultaneously projects possibilities for oneself. Thrownness emphasizes contingency and situated facticity; projection shows how Dasein is future-oriented and constituted by potential ways of being.
Everydayness and the "they" (das Man) describe how social norms and anonymous publicness shape conduct and understanding. "Falling" or "fallenness" denotes how Dasein gets absorbed in the crowd and loses itself in routine, obscuring more authentic possibilities.

Authenticity, Anxiety, and Death
Authenticity involves taking ownership of one's possibilities rather than living according to the impersonal demands of the "they." This existential appropriation requires resoluteness, a confronting of one's finite possibilities.
Heidegger highlights anxiety (Angst) as a mood that discloses the nothingness of everyday concerns and permits a confrontation with Being. Being-toward-death is the ultimate possibility that individualizes Dasein; facing death authentically enables a more truthful relation to one's ownmost potentiality.

Temporality and Legacy
Temporality is central: for Heidegger, time is not a sequence of moments but the horizon that makes sense of Dasein's care and understanding. Past, present, and future interrelate in the unity of temporality, and historicity emerges as the way temporal structures shape communal and cultural forms of existence.
Being and Time transformed 20th-century philosophy by reorienting metaphysical questions toward existential and linguistic conditions of sense. Its influence extends across phenomenology, existentialism, hermeneutics, and later debates about subjectivity, language, and history.