[There still remains the question whether] he who discovers a new world in the depths of the invisible would not do wisely to plant on it a flag known to himself alone, and, like Achilles, "devour his heart in secret;" whether the greatest problems which have ever been guessed on earth had not better have remained buried in the brain which had found the key to them, and whether the deepest thinkers - those whose hand has been boldest in drawing aside the veil, and their eye keenest in fathoming the mysteries beyond it - had not better, like the prophetess of Ilion, have kept for heaven, and heaven only, secrets and mysteries which human tongue cannot truly express, nor human intelligence conceive.