1. God’s work in these three ages differs according to the nature of each age, but at each stage it accords with man’s needs—or rather, it varies according to the tricks that Satan employs in God’s war against it. The purpose of God’s work is to defeat Satan, to make manifest God’s wisdom and omnipotence, to expose all Satan’s tricks and thereby to save all of humanity, which lives under its domain. It is to show God’s wisdom and omnipotence while at the same time revealing the hideousness of Satan. Moreover, it is to teach God’s creations to discriminate between good and evil, to recognize that God is the Ruler of all things, to see clearly that Satan is humanity’s foe, the lowest of the low, the evil one, and to make the difference between good and evil, truth and falsehood, holiness and filth, greatness and baseness, as clear as day.
2. This way, ignorant humanity may bear witness to God that it is not God who corrupts humanity, and only God—the Creator—can save humanity, can bestow upon them things for enjoyment; and they may come to know that God is the Ruler of all things and Satan is merely one of His creations, which later turned against Him. God’s six-thousand-year management plan is divided into three stages in order to achieve the following effect: to allow God’s creations to be God’s witnesses, to know God’s will, to see that God is the truth.
from “The Truth Concerning the Work in the Age of Redemption” in The Word Appears in the Flesh