Verse 4 talks about the “simple” receiving prudence, and young men learning knowledge and discretion.
The word, “simple” in this verse doesn’t mean mentally handicapped, as some people now use the word. It is translated from words that mean a person who is easily persuaded or lacks common sense and good judgment. It can also mean someone who is naïve, immature, or lacks experience.
Prudence, according to The American Heritage® Dictionary Online, means to exercise good judgment, common sense… even caution, especially in the conduct of practical matters. It suggests wise self-restraint, as in resisting a rash impulse, and implies the ability to foresee and make provision for what may happen. It also implies discretion, as out of concern for moral or social repercussions. These are all things that I would want to strive for.
As “simple” also means immature or lacking experience, you can see how learning wisdom would help a young person to learn knowledge and discretion. I think I would rather learn these things from the experience of others, or from the Word of God rather than from having to stumble through life, hopefully living long enough, to get them through my own experience!!! It also makes me think, again, about parenting and/or mentoring those who are younger than we are in age OR in spiritual understanding.
Discretion, as mentioned before, also speaks about understanding that there could be moral or social repercussions from our speech or our actions. This is sort of like “looking before you leap” or not having “diarrhea of the mouth…” James 3 talks about keeping the tongue under control and how it can be a “deadly poison” (3:8), and in James 3:13- 18 the Bible talks about two kinds of wisdom.
“13 Who is wise and understanding among you? Let him show it by his good life, by deeds done in the humility that comes from wisdom. 14 But if you harbor bitter envy and selfish ambition in your hearts, do not boast about it or deny the truth. 15 Such "wisdom" does not come down from heaven but is earthly, unspiritual, of the devil. 16 For where you have envy and selfish ambition, there you find disorder and every evil practice.
17 But the wisdom that comes from heaven is first of all pure; then peace-loving, considerate, submissive, full of mercy and good fruit, impartial and sincere. 18 Peacemakers who sow in peace raise a harvest of righteousness.” (NIV)