ACT III of The Tempest: Prosper's turning point!

           Miranda and Ferdinand want to get married which makes Prospero extremely happy. Getting Miranda and Ferdinand engaged is a part of Prospero's master plan to gain his Dukedom back. Ferdinand is the king's son and that would give his daughter more authority, but for the meanwhile Prospero commands Ferdinand to do Caliban's duties. This demonstrates to us, the readers, that Prospero not only wants a prince for his daughter, but a hard working man that is willing to do what it takes for her. As he pretends to be asleep Miranda is able to profess her love to Ferdinand. The happiness Prospero expresses at the end of scene one suggests that he is getting a step closer to success. The fact that Prospero is arranging this marriage for his own selfish reasons emphasizes that he's not a very pure character, therefore; as an audience we do not sympathize with him anymore.

           He is a clever man who knows exactly what he is doing. Miranda has never seen another man other than her  father and Caliban, so when she met Ferdinand she immediately falls in love. Revenge and authority over something greater than the island in which  they inhabit is ultimately what he is seeking. By infiltrating  the royal family be may be able to obtain that. In the event in which Ferdinand and Miranda get engaged will be the biggest turning point for Prospero. He would have ensured his place with in the royal family.