What does Ahab's Metaphor pasteboard masks to visible objects mean?

Ahab uses this metaphor to represent why he needs to kill Moby Dick. He compares his revenge and hate to pasteboard (cardboard) masks or walls around his mind allowing him to think of nothing else but his revenge. He says that unless he breaks through these masks (kills the whale) he will not be at peace and it will drive him crazy.

He is talking about the Power or Force behind all parts of Nature. Ahab believes it is a malicious Force that creates everything man sees; so, when we see beauty in the world and experience benevolence in Nature, we are being deceived if we believe the Force is kind or benevolent or loving. It is evil; and Moby Dick is not a just a whale-he is the embodiment of the Evil that creates human suffering for his own pleasure. And the closest thing Ahab can do to striking the Force is to kill its embodiment-the white whale that caused his suffering. Ahab believes GOD is evil. Ralph Waldo Emerson admired Melville's work, but he thought this belief went a little "overboard" (if you'll excuse the pun).