God has good reasons for allowing evil to exist.
1. As sin came into the world by one man’s rebellious act of sin so death came into the world, death spread to all people on all who sin (Romans 5:12). By the first sin and the judgment of the law, all flesh became weak and sinful unto death (Romans 3:19–20; 5:12, 17, 19).
2. Sin and death exist by human rebellion contrary to God’s identity and attributes (Romans 1:18–21; 5:11–21; cf. Acts 17:30–31). Evil is rebellion against God, against His holy character, and against the design of His creation (Isaiah 5:20; 55:8–9; cf. 1 Corinthians 6:16). Without God, no one could explain the existence of evil nor overcome it (cf. Romans 2:12–15). Without God, evil actions would be evil only for those who are offended and disgusted by them and for those who detest and abhor them.
3. The knowledge of good and evil brought judgment and condemnation of any rebellion against God as sin. This judgment weakened all flesh to death with its suffering for all who are born including innocent children (Genesis 3; Romans 3:19–20; 5:11–21). The result of judgment by the law of good and evil caused all flesh to become weak (Matthew 26:41; Mark 14:38). Furthermore, people are weakened to be susceptible to the rebellion of sin and sin living in the flesh (Romans 7:14–8:4).
4. God restores every faithful and pure person to eternal life on the last day. God overcomes death in Jesus’s resurrection (Romans 6:9–10; 1 Corinthians 15:51–57). God will give eternal life by restoring creation from corruption and decay. This is the redemption of the faithful by bodily resurrecting them from the dead (Romans 8:18–25; 2 Corinthians 4:17).
5. God will rescue the innocent and the faithful in the end so that there will be no more mourning, crying, or pain anymore (Revelation 21:4). In the paradise of the new earth, God promises to heal the faithful among the nations so that none who believe is accursed (22:2–3). God works all things for good (Romans 8:28).
6. God allows rebellion and its evil for the complete and ultimate destruction of evil and sin through Jesus Christ (Hebrews 2:14–18; 1 John 3:8).
7. God allows people who sin and rebel to continue to live by God’s mercy and so have the opportunity to repent, because God loves all and wants everyone to repent and be saved (1 Timothy 2:4; 2 Peter 3:9). God made humanity in His likeness and gives humanity the ability to trust Him and to repent from the rebellion of sin.
8. God’s gives strength to the faithful to become holy and live in holiness (Romans 6:15–19; 1 Corinthians 10:12–13; 1 Thessalonians 5:23–24).
9. God allows human rebellion and its evil that allows the greatest acts of good — repentance, mercy, compassion, forgiveness, comfort, and relief — that cannot exist otherwise (Luke 5:32; 6:20–49).
10. God allows human rebellion that produces evil with its suffering so that God’s grace strengthens a person’s character through suffering that cannot develop without suffering (Romans 5:3–5; 8:16, 28; 2 Corinthians 12:7–10).
11. While God allows human rebellion to weaken flesh unto death, decay, and suffering, God gives peace and rest by the grace of God in this life now in Jesus Christ (Romans 8:16; Philippians 1:27–30; James 1:2–4; cf. 1 Peter 3:14; 4:1, 12; 5:10).