Read the excerpt from Chapter 28 of Moby-Dick . It resembled that perpendicular seam sometimes made in the straight, lofty trunk of a great tree, when the upper lightning tearingly darts down it, and without wrenching a single twig, peels and grooves out the bark from top to bottom, ere running off into the soil, leaving the tree still greenly alive, but branded. Melville’s description of Ahab’s scar in this excerpt best develops which theme in the novel?