The Tempest Theme of Compassion and Forgiveness

"The rarer action is / In virtue than in vengeance" (5.1.2).  This is Prospero's startling revelation after years of living in exile and plotting his return to Italy.  The Tempest's emphasis on mercy and forgiveness are hallmarks of Shakespeare's "romances," four plays (The Tempest, Pericles, The Winter's Tale, and Cymbeline) written late in the playwright's career.  Prospero's capacity to forgive those who have betrayed him, Miranda's empathy, Ariel's mercy, and Gonzalo's thoughtfulness dramatize the triumph of the human spirit.

1. Does forgiveness come naturally to Prospero? If it does, why was it so important to orchestrate the whole tempest? So he could publicly forgive everyone for stuff they weren't even sorry about? What's the real motivation here?
2. Ariel says he would feel tenderness towards the enchanted men if he were "human." Can we take it for granted that mercy is a natural human sentiment?
3. What is it that prompts Prospero to forgive his enemies?
4. How do we reconcile Prospero's constant petty harassments of Caliban with the wonderfully forgiving Prospero later in the play? Has Prospero changed, or is he merciful and magnanimous only on a human-to-human basis? Is this a colonial thing again, where everyone's equal but some are more equal than others?

Mercy does come naturally to man in the state of nature. Miranda, full of empathy and sympathy, is evidence of this. Prospero and the others in the play do not come to mercy so easily because they have been ruined by civilization.