Prospero controls the island, Ariel, Caliban, the weather and, largely, the plot. Shakespeare asks whether such power is used justly.
Caliban's claim 'This island's mine / by Sycorax my mother' resonates with post-colonial readings. Prospero arrived and enslaved the island's original inhabitant. This is one of the most debated aspects of the play in modern interpretation.
Prospero chooses forgiveness over revenge. His speech — 'The rarer action is / In virtue than in vengeance' — is the play's moral centre.
Ariel desires freedom; Caliban desires freedom from Prospero's control. The play explores what freedom means and what people will do to achieve it.
The Tempest is widely read as Shakespeare's farewell to the theatre. When Prospero breaks his staff and drowns his books, it can be read as the playwright's own farewell to the art of illusion.