Martin Heidegger (26 September 1889 – 26 May 1976) was a German philosopher widely regarded as one of the most important and influential thinkers of the twentieth century. His work was central to the development of phenomenology, hermeneutics, and existentialism, and has had a considerable impact on fields ranging from philosophy and theology to literary theory, psychiatry, and political philosophy.
Heidegger's magnum opus, Being and Time (1927), is widely considered one of the most significant works of modern philosophy. In it, he introduced the concept of Dasein ("being-there") to describe the distinctive character of human existence, arguing that humans possess a "pre-ontological" understanding of being that shapes how they live and act, which he analyzed in terms of the unitary structure of "being-in-the-world". Through his analysis of Dasein, Heidegger sought to reawaken what he called "the question of being": the fundamental inquiry into what makes entities intelligible as the entities they are. In other words, Heidegger's governing "question of being" is concerned with what makes beings intelligible as beings.