If this prove
A vision of the Island, one dear son
Shall I twice lose.
– William Shakespeare
The Tempest, Act 5, Scene 1. When Prospero pulls back a curtain to reveal Ferdinand and Miranda playing chess, Alonso is amazed and overwhelmed with joy to see his son alive, having thought he was dead. If this is just another of the illusions produced by this island, then he will lose his dear son twice, he says, referring to Prospero’s powers of magic and illusion.