In Act 1, Scene 2 of The Tempest, Prospero tells his daughter Miranda about how he came to be banished from his dukedom, how they arrived on this island, how they managed to survive, and why he has used his magic to raise this powerful storm. The purpose of the scene is to inform the audience of all the essential details and bring them up to date for what is to follow in the play. It also introduces Ferdinand, who has become separated from the other castaways. Miranda's dialogue is always brief. It is inserted mainly to keep Prospero's long exposition from becoming tedious. At one point Miranda wonders whether she was a burden to her father, since she was still practically a baby when they were marooned on this island.
Was I then to you!
O, a cherubim
Thou wast that did preserve me. Thou didst smile.
Infused with a fortitude from heaven,
When I have deck'd the sea with drops full salt,
Under my burthen groan'd; which raised in me
An undergoing stomach, to bear up
Against what should ensue.
According to Prospero, his daughter was only about three years old when they came to the island. No doubt he had some difficulties in caring for such a young child, but she repaid him by providing him with company and with love. A cherubim is an angel. She was a blessing to her father rather than a trouble. He loves her deeply and is concerned about her happiness. This concern was one of his chief reasons for raising the tempest which will bring Ferdinand to their island and enable Miranda, for the first time in her life, to see another man besides her father and the vile Caliban.
In his long exposition which takes up much of the scene, Prospero tells her they have been on the island for twelve years, which means that she is now only fifteen. Although she doesn't know it, she is about to fall in love with a handsome prince named Ferdinand, who, because of what he is told by the spirit Ariel in one of Shakespeare's most charming songs, believes his father is dead and hence that he has become King of Naples
Full fathom five thy father lies;
Of his bones are coral made;
Those are pearls that were his eyes:
Nothing of him that doth fade
But doth suffer a sea-change
Into something rich and strange.
Sea-nymphs hourly ring his knell
Hark! now I hear them,--Ding-dong, bell.
Miranda's extreme youth, like that of Juliet in Romeo and Juliet, once again suggests that girls married and became mothers much earlier in Shakespeare's time than they do today. Prospero seems to feel that she is fully mature, and he wishes to see her married to Ferdinand.