1)
What does the Ba'ar not understand?
1.
Rashi: What it says after this (verse 8). Radak - that the success of Resha'im is in order "Lehishamdam Adei Ad." Only Chachamim know this. Malbim - this was Hashem's deep thought, that fools not understand this, to leave room for choice!
2.
Radak: The previous verse (Your actions and the depth of Your thoughts).
