Martin Heidegger
1889 CE – 1976 CE · Contemporary Era
“The fundamental question of philosophy is the question of Being: and we have forgotten to ask it.”
Biography
Heidegger's Being and Time is a central and notoriously difficult work of 20th-century philosophy. He argued that Western philosophy has forgotten the question of Being and that human existence (Dasein) is uniquely characterized by its concern for its own being and its awareness of mortality. His legacy is deeply and unresolvedly complicated: he was a member of the Nazi Party from 1933 until its dissolution, served as Rector of the University of Freiburg under the regime with genuine enthusiasm, and the Black Notebooks -- private journals published in 2014 -- reveal that his antisemitism was not incidental but woven into his philosophical worldview. Whether his philosophy can be cleanly separated from his politics remains one of the genuinely open questions in the history of thought, and any honest engagement with Heidegger must hold that question open rather than dismissing it as biographical accident.
Major Works
Key Arguments
Click “Philosophy 101” to read the full exploration of each argument.
Being-toward-Death
Authentic existence requires confronting our own mortality directly. Only by facing the certainty and indefiniteness of death can we be liberated from 'the They' and genuinely engage with our own existence.
Why it matters: Reshaped existentialist philosophy and influenced theology, psychology, literary theory, and environmental thought.
The Question of Being
Western philosophy has forgotten its most fundamental question: What does it mean for something to be? We talk constantly about beings, things that exist, but we never ask about Being itself, the condition that makes it possible for anything to show up at all. Heidegger argued that this 'forgetting of Being' has shaped the entire Western tradition since Plato, and that recovering the question requires a bold rethinking of philosophy from the ground up.
Why it matters: The central project of Heidegger's career and the most ambitious philosophical undertaking of the 20th century. Being and Time (1927) reframed the entire history of Western philosophy as a progressive forgetting, and its influence on Continental philosophy, theology, hermeneutics, and literary theory has been vast, even among thinkers who ultimately reject Heidegger's conclusions.
Dasein and Thrownness
Human beings are not detached observers of the world, we are 'thrown' into a situation we did not choose: a particular body, culture, language, historical moment. Heidegger called human existence Dasein ('being-there') to emphasize that we are always already embedded in a world of meaning, projects, and relationships. We do not first exist and then enter the world; we exist only as beings-in-the-world. Understanding this changes everything about how we approach knowledge, identity, and freedom.
Why it matters: Demolished the Cartesian picture of the self as a thinking thing locked inside a body, looking out at an external world. Heidegger's analysis of human existence as fundamentally situated, embodied, and world-engaged influenced Sartre's existentialism, Merleau-Ponty's phenomenology of the body, Gadamer's hermeneutics, and contemporary cognitive science's rejection of the mind-as-computer model.
Frequently Asked Questions
Lasting Influence
A defining figure in 20th-century philosophy. Shaped existentialism, hermeneutics, and deconstruction. The Black Notebooks make clear that his politics were not a biographical accident; whether his philosophical project can survive separation from those politics remains genuinely unresolved.
Related Philosophers
Maurice Merleau-Ponty
1908 CE – 1961 CE
We do not have bodies; we are our bodies. Perception is the foundation of all knowledge.
Søren Kierkegaard
1813 CE – 1855 CE
Truth is subjective; authentic existence demands passionate commitment in the face of uncertainty.
Edmund Husserl
1859 CE – 1938 CE
Philosophy must return 'to the things themselves' by studying the structures of conscious experience.
Jean-Paul Sartre
1905 CE – 1980 CE
Existence precedes essence: we are condemned to be free and must create ourselves through choice.
Thales of Miletus
624 BCE – 546 BCE
Water is the fundamental substance underlying all of reality.
Heraclitus
535 BCE – 475 BCE
Everything flows; change is the fundamental nature of reality.
Your Reading Path
The Companion Guide
Seven eras of philosophy in one volume — reading lists, key terms, journal prompts · $19.99