How does Shakespeare explore the theme of betrayal in The Tempest?
The Tempest is driven by Prospero’s desire to avenge his betrayal. He says that he loved his brother Antonio more than anyone in the world other than himself. Prospero, “being transported / And rapt in secret studies” (reading, possibly studying sorcery), let Antonio take control of his dukedom. Like Lear’s daughters in King Lear, who presumed themselves rulers when their father gave them his kingdom, Antonio thought himself to be the role he assumed. He made a deal with King Alonso of Naples, “an enemy / To me [Prospero] inveterate,” who agreed to support Antonio’s bid for power. Instead of killing the popular Prospero, the conspirators put him and his young daughter, Miranda, on a rickety boat. The two unexpectedly survived their journey by landing on a desert island.
Prospero has it out for Antonio and Alonso, who crash on his island after Prospero has Ariel create a storm. Alonso’s brother Sebastian is also there, and he seems interested in following in Antonio’s steps. He plans to kill his brother to take the throne: “Thy case, dear friend, / Shall be my precedent; as thou got'st Milan, / I'll come by Naples.” Ariel rebukes and frightens Antonio, Alonso, and Sebastian, referring to them as “three men of sin.” However, Prospero forgives them in the end.
Prospero and Caliban’s relationship demonstrates another example of betrayal. Caliban accuses Prospero of taking advantage of him:
When thou camest first,
Thou strokedst me and madest much of me,
... and then I loved thee
And show'd thee all the qualities o' the isle...
Prospero calls him a liar and claims that Caliban betrayed him, repaying his kindness by trying to violate Miranda. Whatever the truth, Caliban certainly seeks to cross Prospero now. When he meets Stephano, who gives him drink, Caliban says he will serve Stephano if he helps kill Prospero. In spite of these many betrayals of trust, The Tempest ends not in revenge, but in forgiveness.