Atonement is the passing of sin from mankind to Jesus. Different christian groups believe that it happens in different ways. Christians emphasise that Jesus is the Saviour of the world and through his death the sins of mankind have been forgiven.
The first idea is that Jesus liberates mankind from sin by giving his own life to Satan. The victory over Satan happens when mans imperfict life is swapped for Jesus perfect life, this theory was first used in the fourth-century and was based on verses such as Mark 10:45 - "the Son of Man came … to give his life as a ransom for the many".
The second idea is that man's sins are a debt to god who is head of everything so he cant do nothing if everyone is sinning and so only a perfect sacrifice, Jesus who is part man and god, could cancel this debt. The third idea is that Jesus death on the cross shows gods love and mankind is moved by this act of love and so is transformed by the power of the holy spirit
