God has good reasons for allowing evil to exist.
1. Evil is rebellion against God, His holy character, and against the design of His creation. Without God, no one could explain the existence of evil nor overcome it. Without God, evil acts would be evil only for those who are offended and disgusted by it and so detest and abhor it.
2. The knowledge of right and wrong weakened all flesh to death and its suffering for all who are born (Genesis 3; Romans 3:19–20). All flesh is weak (Matthew 26:41; Mark 14:38). By Adam’s sin, all flesh became weak and sinful in the sense of being susceptible to sin (Romans 5:12, 17, 19; 8:3).
3. God will make all things right. 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 paradise, God promises to heal the faithful among the nations so that no one is accursed (22:2–3).
4. God restores every innocent and faithful person to life on the last day. God overcomes death in Jesus’s resurrection. 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 allows evil to a great extent for the complete and ultimate destruction of evil and sin through Jesus Christ (Hebrews 2:14–18; 1 John 3:8).
6. God allows evil so that people who sin can continue living by God’s mercy to have opportunity to repent, because God loves all and wants everyone to repent and be saved (1 Timothy 2:4; 2 Peter 3:9).
7. God made humanity in His likeness and gives humanity the ability to choose to trust Him and to repent from sin. God’s gives strength to the faithful to live in holiness (Romans 6:15–19; 1 Corinthians 10:12–13).
8. God allows evil and that allows the greatest acts of good — repentance, mercy, compassion, forgiveness, comfort, and relief — that cannot exist otherwise (Luke 5:32; 6:20–49).
9. God allows evil and suffering as God’s grace strengthens a person’s character through suffering that cannot exist without suffering (Romans 5:3–5; 8:16, 28; 2 Corinthians 12:7–10).
10. God allows evil to weaken flesh with its suffering yet God gives peace and rest by the grace of God in Jesus Christ (Romans 8:16; Philippians 1:27–30; James 1:2–4; cf. 1 Peter 3:14; 4:1, 12; 5:10).