Ernst Alfred Cassirer (/kɑːˈsɪərər, kə-/; German: [ˈʔɛɐ̯nst kaˈsiːʁɐ]; July 28, 1874 – April 13, 1945) was a German philosopher. Trained within the Neo-Kantian Marburg School, he initially followed his mentor Hermann Cohen in attempting to supply an idealistic philosophy of science.
After Cohen's death, Cassirer developed a theory of symbolism and used it to expand phenomenology of knowledge into a more general philosophy of culture. Cassirer was one of the leading 20th-century advocates of philosophical idealism. His most famous work is the Philosophy of Symbolic Forms (1923–1929).
Born in Breslau in Silesia (modern-day southwest Poland), into a Jewish family, Cassirer studied literature and philosophy at the University of Marburg (where he completed his doctoral work in 1899 with a dissertation on Descartes's analysis of mathematical and natural scientific knowledge entitled Descartes' Kritik der mathematischen und naturwissenschaftlichen Erkenntnis [Descartes' Critique of Mathematical and Scientific Knowledge]) and at the University of Berlin (where he completed his habilitation in 1906 with the dissertation Das Erkenntnisproblem in der Philosophie und Wissenschaft der neueren Zeit: Erster Band [The Problem of Knowledge in Philosophy and Science in the Modern Age: Volume I]).
Politically, Cassirer supported the liberal German Democratic Party (DDP). After working for many years as a Privatdozent at the Friedrich Wilhelm University in Berlin, Cassirer was elected in 1919 to the philosophy chair at the newly founded University of Hamburg, where he lectured until 1933, supervising amongst others the doctoral theses of Joachim Ritter and Leo Strauss. Because he was Jewish, he left Germany after the Nazis came to power in 1933.
After leaving Germany he taught for a couple of years at the University of Oxford, before becoming a professor at Gothenburg University. When Cassirer considered Sweden too unsafe, he applied for a post at Harvard University, but was rejected because thirty years earlier he had rejected a job offer from them. In 1941 he became a visiting professor at Yale University, then moved to Columbia University in New York City, where he lectured from 1943 until his death in 1945.
Cassirer died of a heart attack in April 1945 in New York City. His grave is located in Westwood, New Jersey, on the Cedar Park Beth-El Cemeteries in the graves of the Congregation Habonim. His son, Heinz Cassirer, was also a Kantian scholar.
Donald Phillip Verene, who published some of Cassirer's papers kept at Yale University, gave this overview of his ideas:
Cassirer's first major published writings were a history of modern thought from the Renaissance to Kant. In accordance with his Marburg neo-Kantianism he concentrated upon epistemology. His reading of the scientific revolution, in books such as The Individual and the Cosmos in Renaissance Philosophy (1927), as a "Platonic" application of mathematics to nature, influenced historians such as E. A. Burtt, E. J. Dijksterhuis, and Alexandre Koyré.
In Substance and Function (1910), he writes about late nineteenth-century developments in physics including relativity theory and the foundations of mathematics. In Einstein's Theory of Relativity (1921) he defended the claim that modern physics supports a neo-Kantian conception of knowledge. He also wrote a book about Quantum mechanics called Determinism and Indeterminism in Modern Physics (1936).
At Hamburg Cassirer discovered the Library of the Cultural Sciences founded by Aby Warburg. Warburg was an art historian who was particularly interested in ritual and myth as sources of surviving forms of emotional expression. In Philosophy of Symbolic Forms (1923–29) Cassirer argues that man (as he put it in his more popular 1944 book Essay on Man) is a "symbolic animal". Whereas animals perceive their world by instincts and direct sensory perception, humans create a universe of symbolic meanings. Cassirer is particularly interested in natural language and myth. He argues that science and mathematics developed from natural language, and religion and art from myth.
In 1929 Cassirer took part in an historically significant encounter with Martin Heidegger in Davos. Cassirer argues that while Kant's Critique of Pure Reason emphasizes human temporality and finitude, he also sought to situate human cognition within a broader conception of humanity. Cassirer challenges Heidegger's relativism by invoking the universal validity of truths discovered by the exact and moral sciences.
Cassirer believed that reason's self-realization leads to human liberation. Mazlish (2000), however, notes that Cassirer in his The Philosophy of the Enlightenment (1932) focuses exclusively on ideas, ignoring the political and social context in which they were produced.
In The Logic of the Cultural Sciences (1942) Cassirer argues that objective and universal validity can be achieved not only in the sciences, but also in practical, cultural, moral, and aesthetic phenomena. Although inter-subjective objective validity in the natural sciences derives from universal laws of nature, Cassirer asserts that an analogous type of inter-subjective objective validity takes place in the cultural sciences.
Cassirer's last work, The Myth of the State (1946), was published posthumously; at one level it is an attempt to understand the intellectual origins of Nazi Germany. Cassirer sees Nazi Germany as a society in which the dangerous power of myth is not checked or subdued by superior forces. The book discusses the opposition of logos and mythos in Greek thought, Plato's Republic, the medieval theory of the state, Machiavelli, Thomas Carlyle's writings on hero worship, the racial theories of Arthur de Gobineau, and Hegel. Cassirer claimed that in 20th century politics there was a return, with the passive acquiescence of Martin Heidegger, to the irrationality of myth, and in particular to a belief that there is such a thing as destiny. Of this passive acquiescence, Cassirer says that in departing from Husserl's belief in an objective, logical basis for philosophy, Heidegger attenuated the ability of philosophy to oppose the resurgence of myth in German politics of the 1930s.
- Leibniz' System in seinem wissenschaftlichen Grundlagen (1902)
- The Problem of Knowledge: Philosophy, Science, and History since Hegel [Das Erkenntnisproblem in der Philosophie und Wissenschaft der neueren Zeit] (1906–1920), English translation 1950 (online edition  )
- "Kant und die moderne Mathematik." Kant-Studien (1907)
- Substance and Function [Substanzbegriff und Funktionsbegriff] (1910) and Einstein's Theory of Relativity [Einsteinschen Relativitätstheorie] (1921), English translation 1923 (online edition  )
- Kant's Life and Thought [Kants Leben und Lehre] (1918), English translation 1981
- Philosophy of Symbolic Forms [Philosophie der symbolischen Formen] (1923–29), English translation 1953–1957 Volume One: Language [Erster Teil: Die Sprache] (1923), English translation 1955 Volume Two: Mythical Thought [Zweiter Teil: Das mythische Denken] (1925), English translation 1955 Volume Three: The Phenomenology of Knowledge [Dritter Teil: Phänomenologie der Erkenntnis] (1929), English translation 1957
- Language and Myth [Sprache und Mythos] (1925), English translation 1946 by Susanne K. Langer
- The Individual and the Cosmos in Renaissance Philosophy [Individuum und Kosmos in der Philosophie der Renaissance] (1927), English translation 1963 by Mario Domandi
- "Erkenntnistheorie nebst den Grenzfragen der Logik und Denkpsychologie." Jahrbücher der Philosophie 3, 31-92 (1927)
- Die Idee der republikanischen Verfassung (1929)
- "Kant und das Problem der Metaphysik. Bemerkungen zu Martin Heideggers Kantinterpretation." Kant-Studien 26, 1-16 (1931)
- Philosophy of the Enlightenment [Die Philosophie der Aufklärung] (1932), English translation 1951
- Determinism and Indeterminism in Modern Physics: Historical and Systematic Studies of the Problem of Causality [Determinismus und Indeterminismus in der modernen Physik] (1936), English translation 1956
- The Logic of the Cultural Sciences [Zur Logik der Kulturwissenschaften] (1942), English translation 2000 by Steve G. Lofts (previously translated in 1961 as The Logic of the Humanities)
- An Essay on Man (written and published in English) (1944) (books.google.com  )
- The Myth of the State (written and published in English) (posthumous) (1946) (books.google.com  )
- Symbol, Myth, and Culture: Essays and Lectures of Ernst Cassirer, 1935-1945, ed. by Donald Phillip Verene (March 11, 1981)
- Ernst Cassirer: Gesammelte Werke. Hamburger Ausgabe. Electronic Edition.  (2016) – The electronic version of the definitive edition of Cassirer's works, published in print by Felix Meiner Verlag, and electronically in the Past Masters series  .
- The Warburg Years (1919-1933): Essays on Language, Art, Myth, and Technology. Translated and with an Introduction by S. G. Lofts with A. Calcagno. New Haven & London: Yale University Press.