In The Tempest, foreshadowing creates a sense of inevitability about the events that happen over the course of the play. Because the play opens with Prospero explaining to Miranda the events that brought them to the island, and contriving to bring all the significant characters together again, we get the sense that Prospero and Miranda’s situation will soon be altered. Throughout, we get hints about Prospero’s decision to give up magic in order to be restored as Duke of Milan. Other events and situations are foreshadowed as well, including the way the social structure on the island upturns social conventions.
Even though Prospero required the use of magic to manipulate the other characters in the play and restore his reputation, in order for him to resume his position as the rightful Duke of Milan, he must renounce magic. For one thing, Prospero’s relentless pursuit of magic is what cost him his dukedom in the first place. He indicates as much when he explains to Miranda how he had retreated into his studies instead of attending to his political responsibilities: “Those [the liberal arts] being all my study, / The government I cast upon my brother / And to my state grew stranger, being transported / And rapt in secret studies” (I.ii.). This quote sets up the choice Prospero must ultimately make: “government” (his title as Duke) versus “secret studies” (magic.) In order to relinquish his hold on the island and return to his duties as the Duke of Milan, Prospero must, as he says in the play’s final scene, “drown my book” (V.i.).
In the play’s opening scene, the Boatswain shows little respect for his most important passenger, the king. While the king would normally be able to command the Boatswain, here the Boatswain ignores him, saying “what cares these roarers for the name of king,” (I.i.) and implying that he cares about his own safety more than anyone else onboard. This suggests that the rules of society are suspended at sea. The reversal of the social order foreshadows the upheavals in social hierarchies that will take place on the island.