 Friedrich Nietzsche (1844–1900) was a German philosopher of the late 19th century who challenged the foundations of Christianity and traditional morality. He was interested in the enhancement of individual and cultural health, and believed in life, creativity, power, and down-to-earth realities, rather than those situated in a world beyond. Central to his philosophy is the idea of “life-affirmation,” which involves an honest questioning of all doctrines that drain life’s expansive energies, however socially prevalent and morally entrenched those views might be. Often referred to as one of the first existentialist philosophers along with Søren Kierkegaard (1813–1855), Nietzsche’s revitalizing philosophy has inspired leading figures in all walks of cultural life, including dancers, poets, novelists, painters, psychologists, philosophers, sociologists and social revolutionaries.