Paul as a minister of the gospel is to bring to light the mystery hidden for ages which is the unfolding plan of God's design for the world.  It has now though been revealed to us in Jesus.  God himself has come to earth to live in the lives of his children to save them by his death and resurrection.  To know him is rich and wonderful and yet it is unsearchable.  He is unsearchable!  We can never fully know him, but he does reveal himself and in that would should delight and marvel.