The following is an excerpt from
The MacArthur New Testament Commentary on 1 John 5.
We know that we are of God, and that the whole world lies in the power of the evil one. (1 John 5:19)
Despite the existence of countless political, cultural, and social entities in the world, there are in reality only two realms. It is the comforting privilege of believers, in addition to having eternal life, answered prayer, and victory over sin, to know they belong to God. Though they exist in this world, they are not part of it (John 15:19; 17:14); they are children of God (John 1:12–13), “aliens and strangers” (1 Peter 2:11; cf. 1:1, 17; 1 Chron. 29:15; Ps. 119:19; Heb. 11:13), whose true citizenship is in heaven (Phil. 3:20).
On the other hand, the whole world—its politics, economics, education, entertainment, and, above all, its religion—lies in the power of the evil one. The evil world system is hostile to God and believers (John 15:18–19), as John noted earlier in this epistle. It takes its cue from its ruler, Satan (John 12:31; 14:30; 16:11; cf. Eph. 2:2; 6:12), the archenemy of God and His people. Because the world is completely under Satan’s influence, believers must avoid being contaminated by it (2:15–17; cf. James 1:27).
There is no middle ground, no third option. Everyone is part of God’s kingdom, or of Satan’s. In the words of Jesus, “He who is not with Me is against Me; and he who does not gather with Me, scatters” (Luke 11:23). Or as James scathingly declares, “You adulteresses, do you not know that friendship with the world is hostility toward God? Therefore whoever wishes to be a friend of the world makes himself an enemy of God” (James 4:4).