Sin is an immoral act considered to be a transgression of divine law. The doctrine of sin is central to Christianity, since its basic message is about redemption in Christ. Hamartiology, a branch of Christian theology which is the study of sin, describes sin as an act of offence against God by despising his persons and Christian biblical law, and by injuring others. Christian hamartiology is closely related to concepts of natural law, moral theology and Christian ethics. According to Augustine of Hippo (354–430) sin is "a word, deed, or desire in opposition to the eternal law of God," or as scripture states, "sin is the transgression of the law."