Philosophy › The 20th century › Existentialism
Martin Heidegger, Being and Time
1889–1976· Philosopher· Reality, mind & God
Well documentedSolid records, texts or physical evidence.
German philosopher whose Being and Time (1927) asked what it means 'to be', starting from ordinary human existence in the world.
See it on the Philosophy map →The idea
Idea: philosophy forgot to ask what it means to be, and must restart from human existence, which he called Dasein ('being-there'). Being and Time argues we are first practical beings using tools, like a hammer, not detached observers. We drift along with the anonymous 'they' until anxiety about our own death calls us to live authentically. Main objection: his invented jargon invites charges of obscurity. More gravely, he joined the Nazi Party in 1933 as rector of Freiburg University.
Why it matters
He shaped existentialism, hermeneutics, deconstruction and environmental thought, and his Nazism raises lasting questions about judging a thinker's work by his life.
Legacy and sources
Being and Time, a collected edition of about 100 volumes, and his 'Black Notebooks', private journals published from 2014 that contain antisemitic passages.
Still debated
How deeply Nazism and antisemitism shaped his philosophy itself, not just his politics, has been fiercely debated since the Black Notebooks appeared.
Connections (5)
▸Why is there something rather than nothing? was called the fundamental question by Martin Heidegger, Being and TimeWell documented
The connection
Leibniz asked why there is something rather than nothing, and answered with God as the sufficient reason. Heidegger reopened the question without that answer, calling it the first and deepest question of metaphysics. For him it exposes how we take beings for granted and forget the wonder that anything is at all.
When and how
He closed his Freiburg lecture 'What Is Metaphysics?' (1929) with it, and opened his 1935 lectures, published in 1953 as Introduction to Metaphysics, with it.
How we know
The question is stated word for word in both texts, and Heidegger discusses Leibniz's version in other writings.
Debates and open questions
Critics from Carnap onward say the question is empty or unanswerable; defenders say its point is the wonder it provokes, not an answer.
▸Husserl and phenomenology was transformed by Martin Heidegger, Being and TimeWell documented
The connection
Heidegger, Husserl's assistant and chosen successor, kept phenomenology's method of careful description but changed its subject. Husserl studied consciousness; Heidegger argued we are first beings already in the world, practically involved with tools and other people, and that phenomenology should uncover Being itself. Husserl came to see this as a betrayal.
When and how
At Freiburg University, where Heidegger was Husserl's assistant from 1919; Being and Time (1927) was dedicated to Husserl, and Heidegger succeeded to his chair in 1928.
How we know
The dedication, Husserl's critical marginal notes in his copy of Being and Time, and their letters document both the debt and the break.
Debates and open questions
Whether Heidegger misread Husserl or exposed real limits is debated, as is his conduct after 1933; the dedication was dropped from the 1941 edition.
▸Martin Heidegger, Being and Time influenced Jean-Paul SartreWell documented
The connection
Sartre adopted much of Being and Time: humans as beings whose own existence is at issue for them, the flight into the anonymous crowd, anxiety and authenticity. Being and Nothingness recast these into a philosophy of radical individual freedom. Heidegger rejected the result, denying he was an existentialist or a humanist.
When and how
Sartre studied Heidegger in Berlin in 1933–34 and again in a German POW camp in 1940–41; Heidegger replied in his 'Letter on Humanism' (1947).
How we know
Being and Nothingness cites Heidegger throughout; the Letter on Humanism quotes and rejects Sartre's 1945 lecture.
Debates and open questions
Whether Sartre misread Heidegger, for instance by rendering Dasein as 'human reality', was long debated in France; Heidegger thought he had.
▸Martin Heidegger, Being and Time taught Hannah ArendtWell documented
The connection
Arendt studied with Heidegger at Marburg at 18, and they had a secret love affair. His way of rethinking basic concepts from their Greek roots shaped her work, but she turned it toward politics, plurality and action, which she thought he neglected. She condemned his Nazism yet later helped revive his reputation in America.
When and how
Marburg University, 1924–25; she left to study with Karl Jaspers in Heidelberg in 1926 and renewed contact with Heidegger in Freiburg in 1950.
How we know
Their letters, published in 1998, document the relationship; her books engage his ideas, often without naming him.
Debates and open questions
How much his thought shaped hers, and whether her postwar loyalty to him was a lapse in judgment, are still debated.
▸Martin Heidegger, Being and Time engaged with The Kyoto School (Nishida Kitaro)Well documented
The connection
Several Kyoto School thinkers went to Germany to study with Heidegger, whose questions about Being and nothingness seemed close to Buddhist ideas of emptiness. They engaged him as ally and rival: Nishida and Nishitani argued that Zen's 'absolute nothingness' went deeper than Heidegger's nothing. Heidegger in turn took interest in East Asian thought.
When and how
Tanabe Hajime studied at Freiburg in 1922–23, Kuki Shūzō with Heidegger at Marburg in 1927–28, and Nishitani Keiji with Heidegger at Freiburg in 1937–39.
How we know
Tanabe's 1924 essay was among the first published discussions of Heidegger anywhere; Heidegger's 'Dialogue on Language' (1959) recounts talks with a Japanese visitor.
Debates and open questions
How much Heidegger learned from East Asian thought, rather than only teaching it, is debated; Reinhard May argued for hidden Daoist and Zen sources.