Kierkegaard and Nietzsche
Søren Kierkegaard and Friedrich Nietzsche were two of the first philosophers considered fundamental to the existentialist movement, though neither used the term "existentialism" and it is unclear whether they would have supported the existentialism of the 20th century. They focused on subjective human experience rather than the objective truths of mathematics and science, which they believed were too detached or observational to truly get at the human experience. Like Pascal, they were interested in people's quiet struggle with the apparent meaninglessness of life and the use of diversion to escape from boredom. Unlike Pascal, Kierkegaard and Nietzsche also considered the role of making free choices, particularly regarding fundamental values and beliefs, and how such choices change the nature and identity of the chooser. Kierkegaard's knight of faith and Nietzsche's Übermensch are representative of people who exhibit Freedom, in that they define the nature of their own existence. Nietzsche's idealized individual invents his or her own values and creates the very terms they excel under. By contrast, Kierkegaard, opposed to the level of abstraction in Hegel, and not nearly as hostile (actually welcoming) to Christianity as Nietzsche, argues through a pseudonym that the objective certainty of religious truths (specifically Christian) is not only impossible, but even founded on logical paradoxes. Yet he continues to imply that a leap of faith is a possible means for an individual to reach a higher stage of existence that transcends and contains both an aesthetic and ethical value of life. Kierkegaard and Nietzsche were also precursors to other intellectual movements, including postmodernism, and various strands of psychology. However, Kierkegaard believed that an individual should live in accordance with his or her thinking. This point of view is forced upon religious individuals much more often than upon philosophers, psychologists, or scientists.
The first important literary author also important to existentialism was the Russian Fyodor Dostoyevsky. Dostoyevsky's Notes from Underground portrays a man unable to fit into society and unhappy with the identities he creates for himself. Jean-Paul Sartre, in his book on existentialism Existentialism is a Humanism, quoted Dostoyevsky's The Brothers Karamazov as an example of existential crisis. Sartre attributes Ivan Karamazov's claim, "If God did not exist, everything would be permitted" to Dostoyevsky himself. Other Dostoyevsky novels covered issues raised in existentialist philosophy while presenting story lines divergent from secular existentialism: for example, in Crime and Punishment, the protagonist Raskolnikov experiences an existential crisis and then moves toward a Christian Orthodox worldview similar to that advocated by Dostoyevsky himself.