Starting with Augustine, the Roman Catholic tradition has understood justification as the entire process by which God forgives and then transforms Christians. Based on their reading of the use of "justification" in Paul's letters, the Reformers took justification to refer specifically to God's forgiveness and acceptance. The term "sanctification" was used to refer to the lifelong process of transformation. Thus the Roman Catholic term "justification" effectively includes both what Protestants refer to as "justification" and "sanctification." This difference in definitions can result in confusion, effectively exaggerating the disagreement. However the difference in definitions reflects a difference in substance. In the Protestant concept, justification is a status before God that is entirely the result of God's activity and that continues even when humans sin. Thus using different words for justification and sanctification reflects a distinction between aspects of salvation that are entirely the result of God's activity, and those that involve human cooperation. The Roman Catholic tradition uses a single term, in part, because it does not recognize a distinction of this type. For the Roman Catholic tradition, while everything originates with God, the entire process of justification requires human cooperation, and serious sin compromises it.