humanity, and how do we cope with it?

A second theme is that of the monstrous nature of humanity. It is difficult at some points in the play to distinguish between men and monsters. We can see humanity in Caliban, and we can see monstrous behavior in some men. Prospero notes,

"If I should say, I saw such islanders,—

For, certes, these are people of the island,—

Who, though they are of monstrous shape, yet, note,

Their manners are more gentle-kind than of

Our human generation you shall find

Many, nay, almost any"(Act III Scene III lines 30-35).

A third theme is that of colonialism. Should one culture invade another and have authority over it? What makes one culture superior to another?

Most plays have several themes or main ideas.

The Tempest examines a number of subjects, including forgiveness, betrayal, and greed. Prospero uses magic to seek vengeance on those who have wronged him, but he eventually realizes that “the rarer action is / In virtue than in vengeance.” The spirit Ariel says that Prospero would pity these men if he saw their spell-induced torments. Prospero grasps that if even Ariel, who is not human, feels sorry for the men, he should as well. He confronts his enemies but neither kills nor continues to torture them.

Another theme is betrayal. Prospero feels betrayed by the spiteful Caliban, whom he raised from a child. Caliban sees Prospero’s enslavement of him as a betrayal since he “show'd [Prospero] all the qualities o' the isle, / The fresh springs, brine-pits, barren place and fertile.” Antonio convinces Sebastian to kill his brother Alonso in order to become king. Alonso helped Antonio overthrow Prospero, Antonio’s own brother. Ambition leads to treachery in The Tempest, even though the characters ultimately reconcile.

A final recurring topic in the play is dehumanization through greed. When Trinculo sees the odd Caliban, he immediately thinks of making money by putting him on display in England: “when they will not give a doit to relieve a lame beggar, they will lazy out ten to see a dead Indian.” This pointed comment demonstrates how fascination with the exotic can trump compassion. When Stephano sees Caliban, he has a similar idea: “he's a present for any emperor that ever trod on neat's leather.” Stephano and Trinculo enlist Caliban, who is already enslaved by Prospero, as their servant. Mercy, treason, and exploitation are three of many themes in The Tempest.

Shakespeare's Tempest is an interesting play; it's one of the few that is hard to categorize, and it is one that seems to be completely without background source material, unlike most of his works, which drew from myth and older stories. 

As he usually does in his plays, Shakespeare explores multiple themes through multiple plotlines and character development. Some of the themes in Tempest are:

1. Kinship and relationships as expressed through Prospero's relationship with his brother, his daughter, and his servants. 

2. Uses and abuses of power, again as expressed through Prospero, who has traded the power of governmental authority for the power of words, through books and magic. Shakespeare also addresses how Prospero's power is expressed differently through his servants Ariel and Caliban and his power over the elements.

3. The consequences of knowledge as expressed through the use of magic, which Prospero gives up at the end.

4. The idea of fate vs. human intervention, since though Prospero seems to be able to control everything, he cannot control the way people's emotions and actions will affect the outcome of his machinations.

There are other themes that you may find in your own reading, but these should be enough to get you started.

Magic and the supernatural is a major theme in The Tempest, as King Alonso makes clear:

This is as strange a maze as e'er men trod;
And there is in this business more than nature
Was ever conduct of: some oracle
Must rectify our knowledge. (Act I, Scene v)

Another important theme, closely related to magic, is illusion and reality. The characters consistently mistake the illusory for reality: Ferdinand and Miranda each think the other is a supernatural being; Caliban thinks Stephano is God; and when Prospero reveals himself to Alonso, Alonso does not know if what he sees is real.

Whe'er thou beest he or no,
Or some enchanted trifle to abuse me, 
As late I have been, I do not know. (Act V, Scene i)

Shakespeare also raises the question about how Prospero's story relates to reality, which encouraged a sort of metacognition in theater-goers. Parts of the play are Prospero's representation of events. And, obviously, Caliban raises the issue of civilization versus savagery, very current as Europeans explored the world. Shakespeare seems to take a view contrary to the "noble savage" construct espoused by Montaigne in "On Cannibals." Caliban is the only representative of the inhabitants of the island, and he is a monster, or in Prospero's words, a "hag-seed," "demi-devil," and a "born devil." It should come as no surprise that Europeans described many peoples in lands they explored along similar lines. 

The Tempest begins with a ship being tossed at sea in a storm. The exposition informs the audience who is on the ship (Alonso, Ferdinand, Gonzalo, Sebastian, and Antonio). When Prospero makes his appearance, the audience learns how he has been usurped and exiled by his brother, Antonio, and that he created the storm to shipwreck him on the island as part of a greater plan.

The rising action coincides with the opening storm, in which the passengers jump ship while the sailors stay aboard. The passengers are thereby scattered throughout the island. Prospero lures Ferdinand to Miranda, conspiring to have the two fall in love and marry. While Prospero has Ferdinand slave away, the other royal passengers engage in their own plots: Antonio and Sebastian plot to kill Alonso and Gonzalo, while the two buffoons Trinculo and Stephano conspire with Caliban (a native of the island) to overthrow Prospero.

The climax occurs during the enchanted banquet. Prospero terrorizes the noblemen with Ariel in a frightening form, castigating them for the wrong they have done. Prospero eventually reveals himself and his true identity. Alonso offers to make amends by restoring Prospero to his dukedom. In turn, Prospero reveals that Ferdinand, whom Alonso thought to be dead, is alive and planning to marry Miranda.

In the resolution, Prospero speaks directly to the audience, promising to burn his books and give up magic.