Martin Heidegger (1889–1976) was a German philosopher whose work is predominantly associated with existentialism and phenomenology. His most enduring work, "Being and Time" ("Sein und Zeit," 1927), is considered a seminal text in modern philosophical thought. Born in rural Messkirch, Heidegger was initially influenced by Roman Catholic thought before turning to philosophy, where he became a student of Edmund Husserl, the founder of phenomenology.

Heidegger's philosophy focuses on the question of Being (Sein), distinguishing between the existence of objects (the ontic) and the mode of being (the ontological). He introduced the concept of Dasein, which refers to the unique kind of being that humans possess, characterized by an awareness of existence itself and the capacity for self-interpretation. Through Dasein, Heidegger explores themes of temporality, authenticity, and the nature of consciousness.

His critique of traditional metaphysics, along with his exploration of language and the concept of truth, had a profound influence on subsequent philosophical movements, including existentialism, hermeneutics, deconstruction, and postmodernism. Heidegger's thoughts on technology, art, and poetry further contributed to a diverse range of disciplines beyond philosophy.

Controversy surrounds Heidegger due to his involvement with the Nazi Party during the early 1930s, a period when he also served as the Rector of the University of Freiburg. Subsequent thinkers have debated the extent to which his philosophical views may be disentangled from his political actions during that period. Despite this, his influence remains deeply entrenched within the fabric of 20th-century philosophy.

Heidegger's method of questioning, his evocative language, and the depth of his inquiries into existence continue to stimulate discussions among philosophers, leading to many interpreting his works in various ways. His thought continues to provoke scholarly debate and inspire philosophical investigation regarding the fundamental questions of human existence and the world.