Abstract: Sanctification is achieved by pleading the Atonement made by Christ, and by gradually coming to form true moral beliefs and making oneself naturally inclined to conform to them. It is the function of the Church to facilitate this process. Total corruption occurs when a human yields so constantly to bad desires that he becomes their prisoner and loses the moral beliefs that incline him to resist them.

Keywords: Aquinas, Church, corruption, moral belief, sanctification,