At thy right hand there are pleasures for evermore (Ps. 16: 11)
Understanding is a wellspring of life unto him that hath it: But the instruction of fools is folly (Prov. 16:22).
In the world as it is described by Proverbs, we do not see the wise who know they have wisdom, and the unwise who know that they do not. This is because knowing that you lack wisdom is actually a form of . . . wisdom. The actual division is between those who possess wisdom, and those who falsely think they do.
Notice in this passage that if someone has understanding, that understanding is like an artesian well. It is a wellspring of life to the one who has it. And when it says this, the assumption is that the one who has understanding is the one who is refreshed by it.
The contrast is with the fool. Notice that the fool here is a teacher. He instructs. Not only does he believe he has wisdom to impart, there is frequently a classroom of people assembled in front of him who believe the same thing. Occasionally there will be a wise student in there who can see that the instructor is blowing smoke, but the foolish instructor, who pours out his folly from quart jars, believes that obtaining an audience somehow vindicates him. But the flow does not rise higher than the source, and if a fool teaches, folly fills the curriculum.