The above speech makes a key element of Miranda's character clear.
In The Tempest, Miranda is a sheltered character who has not had much interaction with the world. Her interactions are limited mainly to her father and Caliban. Therefore it might be expected that Miranda is sheltered and even cold and unfeeling. It would not be surprising if Miranda were to look upon the storm (and the ship being tossed about at sea) and find it only interesting, nothing more. Her reaction, however, is quite different.
Instead, this speech proves Miranda is not cold and unfeeling. She begins by saying, "If by your art, my dearest father, you have Put the wild waters in this roar, allay them." She suspects her father may have played a part in the storm, and she begs him to calm the seas so that those at sea might be saved.
She goes even further, however, than showing concern for those at sea. She goes so far as to say, "O, I have suffered With those that I saw suffer." Although she is safe on land, she knows that those at sea are suffering, and she suffers along with them. This proves Miranda is capable of empathy feels for others. She feels that the boat likely had a good person ("noble creature") on board, and she fears the storm has killed someone. She worries about the safety of others and begs her father to do what he can to calm the sea.
As a result, this excerpt best illustrates Miranda's sympathy for others. It proves she is a caring, compassionate, merciful person.
The theme is to enjoy the simple things in life such as the stars and each other. The poem shows that the characters should be doing something else but they prefer to stay under the stars enjoying them
