If there is anything so precious that without it history and the world will be destroyed, where will you keep it? You will naturally want to keep it in the deepest part of your mind. If you desire to place it in the depths of your mind, it needs to be invisible. It is for this very reason that God exists as an invisible being. It is fortunate that He is invisible, for if He were visible how could a great contest to gain Him be avoided? It would be difficult for God to endure the pain of seeing it.

The Way of God's Will Chapter 1-1. The Will of God Translated 1980.