The Sickness unto Death

The Sickness Unto Death (Danish: Sygdommen til Døden) is a book written by Danish philosopher Søren Kierkegaard in 1849 under the pseudonym Anti-Climacus. A work of Christian existentialism, the book is about Kierkegaard's concept of despair, which he equates with the Christian concept of sin, which he terms, "the sin of despair." Walter Lowrie said The Sickness unto Death is a repetition of Fear and Trembling and that the book is even more closely related to The Concept of Anxiety. Kierkegaard used two pseudonyms for opposite purposes. Johannes Climacus says he's not a Christian whereas Anti-Climacus says he's extraordinary Christian.