At the end of the novel, the Narrator travels with George MacDonald to an enormous chessboard, across which chess pieces move constantly. As MacDonald explains, the chessboard symbolizes the universe as God sees it: predetermined, perfectly controlled, and yet utterly mysterious to human beings, who still act with free will within the system God has created.
The Chessboard Quotes in The Great Divorce
Ye saw the choices a bit more clearly than ye could see them on Earth: the lens was clearer. But it was still seen through the lens. Do not ask of a vision in a dream more than a vision in a dream can give.