Friedrich Wilhelm Nietzsche (October 15, 1844 – August 25, 1900) was a nineteenth-century German philosopher. He wrote critiques of religion, morality, contemporary culture, philosophy, and science, using a distinctive style and displaying a fondness for aphorism. Nietzsche's influence remains substantial within and beyond philosophy, notably in existentialism and postmodernism. Nietzsche's style, and his radical questioning of the value and objectivity of truth, raise considerable problems of interpretation, generating an extensive secondary literature in both continental and analytic philosophy. Nonetheless, his key ideas include interpreting tragedy as an affirmation of life, an eternal recurrence that has fallen into numerous interpretations, and a reversal of Platonism.
Nietzsche began his career as a philologist before turning to philosophy. At the age of 24 he became Professor of Classical Philology at the University of Basel, but resigned in 1879 due to health problems, which would plague him for most of his life. In 1889 he exhibited symptoms of a serious mental illness, living out his remaining years in the care of his mother and sister until his death in 1900.