"...In all wisdom and insight He made known to us the mystery of His will.."
*In matters eternal,if it isn't revealed it's concealed. It's either revelation or speculation. Had God determined to withhold inspiration of His Word, we would not know His heart, His provisions or His prohibitions. We would be left to guess what happened before we were born, and what will transpire after we are gone.
Such speculation is exactly what the non-Christian engages in, since he "does not accept the things of the Spirit of God, for they are foolishness to him; and he cannot understand them, because they are spiritually appraised," (I Corinthians 2:14). Notice the distinction between "does not accept" (refusal), and "cannot understand" (inability). Apart from the regenerating and revealing work of the Holy Spirit, there is no spiritual discernment, no comprehending God's workings, wills, and ways.
*For the redeemed one, however, God graciously makes known His perspective (wisdom), and understanding (insight). By the faithful ministry of the resident Holy Spirit, the Christian is able to appraise the spiritual dimensions of life, thereby experiencing a God-awareness unknown to lost humanity.