Any person who does not act wisely, that is, does not follow the warnings and requirements of God, which are founded in infinite wisdom. Hence "a fool" is put for a wicked man, an enemy or neglecter of God, Psalm 14:1 Proverbs 19:1 . So folly is put for wickedness, 2 Samuel 13:12,13 Psalm 38:5 , foolish lusts for wicked lusts, etc. Foolish talking, foolish questions, are vain, empty, unprofitable conversation, 2 Timothy 2:23 .