Søren Aabye Kierkegaard, born in Copenhagen (1813–1855), was a Danish philosopher, theologian, poet, and social critic, widely considered the first existentialist philosopher. Throughout his life, he wrote critical texts on organized religion, Christianity, morality, ethics, psychology, and philosophy of religion, displaying a particular fondness for figures of speech such as metaphor, irony, and allegory. His work "The Sickness Unto Death" (Sygdommen til Døden in Danish), written in 1849 under the pseudonym Anti-Climacus, deals with the concept of despair, equating it with the Christian concept of sin. Many of the themes explored in this work demonstrate an undeniable connection with the topics later explored by Freud.