Franz Kafka (3 July 1883 – 3 June 1924) was an influential German-language writer of novels and short stories, regarded by critics as one of the greatest authors of the 20th century. Kafka was a Modernist and heavily influenced other genres, including existentialism. His works, such as "Die Verwandlung" ("The Metamorphosis"), Der Process (The Trial), and Das Schloss (The Castle), are filled with the themes and archetypes of alienation, physical and psychological brutality, parent-child conflict, characters on a terrifying quest, and mystical transformations.
1.) Sander L. Gilman (2005). Franz Kafka. Reaktion Books. p. 31. ISBN 9781861892546. "Through his consumption of such books Kafka rejected both capitalism and religion as a teenager - declaring himself to be a socialist and an atheist."
2.) "Whilst Kafka had a brief interest in Kabbalah, mysticism, and Yiddish theatre, he rarely attended synagogue and considered himself an atheist." - Benjamin Lazarus, The Jewish Chronicle Online. 
3.) "As an adolescent, he declared himself a socialist as well as an atheist. As a Jew, Kafka was isolated from the German community in Prague, but as a modern intellectual he was also alienated from his own Jewish heritage."
4.) J. E. Luebering, ed. (2009). "Franz Kafka". The 100 Most Influential Writers of All Time. The Rosen Publishing Group. p. 272. ISBN 9781615300969. "Kafka's opposition to established society became apparent when, as an adolescent, he declared himself a socialist as well as an atheist."