Book excerpt: The concept of sin permeates Søren Kierkegaard’s writing. This study looks at the entirety of his works in order to systematize his doctrine of sin. It demonstrates four key aspects: sin as misrelation, sin as untruth, sin as an existence state, and sin as redoubling in the crowd. Upon categorizing Kierkegaard’s doctrine of sin, his writings are examined to determine if his hamartiology is consistent across his numerous pseudonyms. To conclude, the study places Kierkegaard’s doctrine of sin within the broader theological discussion.