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12:23 conceals knowledge. Not out of selfishness but so that he does not parade his knowledge. Wisdom knows when it is right to keep silent and when to speak (26:4, 5; Eccl. 3:7; James 3:17, 18).
proclaims folly. The fool not only has an inflated assessment of his own cleverness (v. 15), but cannot resist showing it off. Such posturing betrays his real foolishness.