The 20th century brought with it upheavals that produced a series of conflicts within philosophy over the basis of knowledge, with classical certainties thought to be overthrown, and new social, economic, scientific and logical problems, 20th-century philosophy was set for a series of attempts to reform and preserve, and to alter or abolish, older knowledge systems. Seminal figures include Sigmund Freud, Friedrich Nietszche, Ernst Mach, John Dewey. Epistemology and its basis was a central concern, as seen from the work of Martin Heidegger, Karl Popper, Claude Lévi-Strauss and Bertrand Russell. Phenomenologically oriented metaphysics undergirded existentialism and finally postmodern philosophy.
List of philosophers
Notable accompanying movements
