本性
Augustine's understanding of the consequences of original sin and the necessity of redeeming grace was developed in the struggle against Pelagius and his Pelagian disciples, Caelestius and Julian of Eclanum, who had been inspired by Rufinus of Syria, a disciple of Theodore of Mopsuestia. They refused to agree original sin wounded human will and mind, insisting human nature was given the power to act, to speak, and to think when God created it. Human nature cannot lose its moral capacity for doing good, but a person is free to act or not act in a righteous way. Pelagius gave an example of eyes: they have capacity for seeing, but a person can make either good or bad use of it.