but the mouth of a fool feeds on folly
The mouth of a fool represents someone who speaks without wisdom or understanding, often leading to destructive outcomes. In biblical times, the fool is characterized by a rejection of wisdom and moral guidance, as seen in Psalm 14:1, where the fool denies God. Feeding on folly suggests a continual consumption and perpetuation of foolishness, indicating a preference for ignorance over truth. This behavior is self-destructive and contrasts sharply with the pursuit of knowledge. The imagery of feeding implies that what one consumes, whether wisdom or folly, will ultimately shape one's character and actions. This principle is echoed in the New Testament, where Jesus teaches that what comes out of the mouth reflects the heart (Matthew 15:18). The fool's reliance on folly underscores the biblical warning against complacency in spiritual and moral growth.

Proverbs 15:14 opens with “A discerning heart….” Discernment is the Spirit-given ability to distinguish truth from error and right from wrong (1 Corinthians 2:14–15; Hebrews 5:14). Scripture portrays such a heart as:

• humble and teachable (Proverbs 9:9; Psalm 25:9)

• tuned to God’s Word (Psalm 119:66; Proverbs 2:2-6)

• quick to examine everything by the standard of revealed truth (Acts 17:11)

Because “the LORD gives wisdom” (Proverbs 2:6), the discerning person depends on Him rather than on self-generated insight (James 1:5).

The verse continues, “…seeks knowledge….” Seeking is active pursuit, not passive curiosity. The wise:

• treasure Scripture daily (Joshua 1:8; Psalm 1:2)

• invite counsel from godly believers (Proverbs 11:14; 27:17)

• value correction (Proverbs 12:1; 19:20)

• apply what they learn (James 1:22)

Knowledge here is moral and spiritual—truth that shapes character and conduct (Colossians 1:9-10). Desire for such knowledge is evidence of loving God “with all your mind” (Matthew 22:37).

In contrast, the second half warns, “…but the mouth of a fool….” A fool in Proverbs is not intellectually deficient but morally stubborn (Psalm 14:1; Proverbs 1:7). His mouth exposes his heart (Luke 6:45). Hallmarks include:

• careless words (Proverbs 10:14; 18:7)

• rapid, opinionated speech (Proverbs 29:11; Ecclesiastes 5:3)

• rejection of reproof (Proverbs 12:15)

Instead of reflecting, he reacts; instead of listening, he lashes out.

The fool’s mouth “feeds on folly.” Like an animal grazing, he continually consumes and spreads nonsense—ideas opposed to God’s wisdom (Proverbs 15:2; 26:11). Folly becomes both his diet and his product:

• gossip, slander, coarse talk (Ephesians 5:4; Proverbs 20:19)

• mockery of righteousness (Proverbs 14:9; 21:24)

• self-promotion and empty boasting (Proverbs 27:22; 2 Timothy 3:2)

His appetite for foolishness hardens his heart (Romans 1:21-22) and influences others for harm (Proverbs 13:20).

Proverbs 15:14 contrasts two heart-conditions revealed by speech. The discerning heart hungers for God’s truth and seeks it actively, while the fool’s mouth craves and circulates empty foolishness. Our words therefore serve as a spiritual barometer: they show whether we are diligently pursuing the knowledge that leads to life or mindlessly grazing on folly that leads to ruin.

Σοφία γάρ ἐστι καὶ μαθεῖν ο} μὴ νοεῖς

"To learn what thou hast never thought is wisdom." The mouth of fools. Another reading, is "the face of fools;" but the former is more suitable to what follows. Feedeth on foolishness. So the Vulgate and Septuagint, "The mouth of the undisciplined knoweth evil." The fool is always gaping and devouring every silly, or slanderous, or wicked word that comes in his way, and in his turn utters and disseminates it.

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