The setting is the Whaleman's Chapel, and everything about it reminds the visitor of life and death at sea. Father Mapple is like the captain of the ship, the congregation his crew. When he enters the pulpit, he pulls the rope ladder up after him, symbolically cutting himself off, for the time, from worldly matters. This act foreshadows the way in which the Pequod, when set at sea, becomes its own microcosm (a symbolic little world), peopled by a diverse crew, isolated, captained not by the spiritual Father Mapple but by the troubled, rebellious, angry Ahab.
The sermon centers on the Old Testament story of Jonah and the whale. Its theme is that we must serve God by transcending our own self-interests: "And if we obey God, we must disobey ourselves; and it is in this disobeying ourselves, wherein the hardness of obeying God consists," Mapple states. This theme continues throughout the novel; the sermon sets its tone. The reader should remember this sermon in relationship to Ahab, who sins in numerous ways throughout the book but never repents and whose greatest sin is that he abjures all obligation to everything but his own desire for revenge.
