How did Martin Heidegger influence existentialism, hermeneutics, and deconstruction?

Martin Heidegger’s work fundamentally reshaped 20th-century philosophy by challenging traditional metaphysical assumptions and shifting the focus of inquiry toward the nature of human existence.12

Existentialism

Heidegger is a central figure in existentialism. By replacing the Cartesian concept of a "thinking subject" with Dasein—or "being-there"—he argued that human existence is defined by "Being-in-the-world," characterized by practical involvements and commitments rather than cognitive isolation. His analysis of themes such as angst, finitude, and authenticity in Being and Time profoundly influenced the development of existentialist thought.1342

Hermeneutics

Heidegger’s approach contributed to the rise of philosophical hermeneutics. By emphasizing that human understanding is always situated within a world of prior commitments and historical contexts, he moved hermeneutics beyond mere textual interpretation toward an ontological investigation of how humans disclose and interpret their own Being.142

Deconstruction

Heidegger’s project of "dismantling" or "destroying" the history of ontology provided the direct inspiration for Jacques Derrida’s deconstruction. Derrida adopted Heidegger’s critical stance toward Western metaphysics to examine and displace the binary oppositions—such as speech versus writing—that have historically structured philosophical thought.56