Foolishness is the result of a person misusing the intelligence God has given him. A fool uses his reasoning skills to make wrong decisions. The most basic type of foolishness is denying God’s existence or saying “no” to God (Psalm 14:1). The Bible associates folly with a quick temper (Proverbs 14:16–17), perverse speech (Proverbs 19:1), and disobedience to parents (Proverbs 15:5). We are born with an innate foolishness, but discipline will help train us in wisdom (Proverbs 22:15).
Proverbs 19:3 says that foolishness is counterproductive: “A person’s own folly leads to their ruin.” Jesus in Mark 7:22 uses a word which means “senselessness” and is translated “folly.” In that context Jesus describes what comes out of the heart of man and defiles him. Foolishness is one of the evidences that man has a defiled, sinful nature. Proverbs 24:9 says, “The schemes of folly are sin.” Foolishness, then, is really the breaking of God’s law, for sin is lawlessness (1 John 3:4).
To the fool, God’s way is foolishness. “The message of the cross is foolishness to those who are perishing.” (1 Corinthians 1:18; cf. verse 23). The gospel seems to be foolishness to the unsaved because it doesn’t make sense to them. The fool is completely out of phase with God’s wisdom. The gospel goes against the unbeliever’s native intelligence and reason, yet “God was pleased through the foolishness of what was preached to save those who believe” (1 Corinthians 1:21).
The believer in Christ receives the very nature of God (2 Peter 1:4), which includes the mind of Christ (1 Corinthians 2:16). By relying on the Holy Spirit’s indwelling power, the believer can reject foolishness. His thoughts can please the Lord, and he can make decisions that glorify God as he enriches his life and the lives of those around him (Philippians 4:8–9; Ephesians 5:18—6:4).
When it comes to our eternal destiny, one is either a fool, meaning he rejects the gospel of Christ, or one is wise, meaning he believes in Christ and commits his life to Him (see Matthew 7:24–27). The believer discovers that the gospel—what he thought was foolishness—is in reality the wisdom of God providing him eternal salvation.