Modern psychology can give greater illumination on the doctrine of the Atonement than on any other Christian truth. This chapter considers what this illumination is, but in order to set it in the right perspective, and examines what light psychology can give us on the doctrine of sin. It suggests that there is an element of satisfaction in the atonement, but it is not satisfaction to God, but satisfaction in God—the satisfaction that came to Him from giving Himself to the utmost for the sinners He loved. The sinner by his frequent sinning becomes hardened, and this makes him less able to feel such an appeal, with the result that the man who needs the cross most is the one least able to respond to it. If sin were, as some of the Greeks always taught, a matter of the intellect, then perhaps a revelation would be adequate, and its grasp by the intellect or understanding would suffice.