Gerald Bivens

Existentialism is a primarily European philosophical movement that flourished around the middle of the 20th century. Although existentialism is a 20th-century movement, the founders of existentialist philosophy were both 19th-century figures—Søren Kierkegaard (1813-1855) and Friedrich Nietzsche (1844-1900)—whose philosophical principles did not take root in mainstream academic philosophy until the 20th century. ...Although commentators have attempted to define existentialism in a variety of ways, a useful way to approach it is to focus on a basic irrationalism shared by existentialist thinkers. To understand this irrationalism, and thus to give ourselves a preliminary definition of existentialism we must first understand the type of rationalism that existentialist irrationalism opposed. ...In opposition to the Platonist claim that things in the world are what they are in accordance with rational, unambiguous principles, that the world is rational, and thus that ambiguities in the world are merely apparent; the existentialist claims that things really are ambiguous, that there are no unambiguous principles constituting that world—the world, for the existentialist, is irrational.¹