Shakespeare wrote The Tempest between 1610 and 1611, 30 to 31 years after Michel de Montaigne published an essay titled "On Cannibals" in 1580. During this same time period, the New World was being colonized, and Montaigne's essay sets out to describe the natives as "cannibals," synonymous with savages, and to argue that modernizing and taming such cannibals/savages is in alignment with "Nature," meaning a good and natural thing to happen ("On Cannibals"). It has been argued by scholars like Michael O'Toole, in his essay "Shakespeare's Natives: Ariel and Caliban in The Tempest," that Shakespeare referred to colonization in his characters in order refute claims made by Montaigne in his essay.
According to O'Toole, we can especially see Shakespeare referring to colonization in his characters Ariel and Caliban. Both characters are natives of the island and have been enslaved by Prospero just as natives of the New World were enslaved in colonial times. What's more, both are extremely different characters. O'Toole points out that Ariel is very submissive towards Prospero, while Caliban is very rebellious. Prospero even describes Caliban as a monster who is "born devil" and cannot be changed, but what is paticularly ironic is that, as Dr. M. Fogiel, editor of MAXnotes to The Tempest, phrases it, Caliban is "given some of the most poetic lines in the play" (eNotes, "List of Characters").
O'Toole argues that we can learn two different arguments Shakespeare is making about "colonized subjects" by looking at the "differing attitudes of these subjects towards their master" ("Shakespeare's Natives"). On the one hand, Prospero freed Ariel from a pine tree in which he had been imprisoned for 12 years by a witch named Sycorax, Caliban's mother; hence, Ariel's willingness to serve Prospero is a result of Ariel's genuine grattitude. In addition, Prospero has promised to eventually free Ariel, which also adds to Ariel's willingness to serve. On the other hand, while Caliban first loved Prospero for treating him better than his evil mother did, Caliban develops resentment towards Prospero because he believes Prospero is taking away an island Caliban sees as his own and enslaving him; for Caliban, as phrased by O'Toole, "It was autonomy that Caliban professed to want, not slavery" ("Shakespeare's Natives"). Citing Caliban's speech in Act 1, Scene 2, lines 331-44, O'Toole demonstrates Caliban's perspective:
This island's mine by Sycorax my mother,
Which thou tak'st from me. When thou cam'st first,
Thou strok'st me and made much of me ...
... and then I loved thee ...
Cursed be I that did so ...
For I am all the subjects tht you have,
Which first was mine own king; and here you sty me
In this hard rock, whiles you do keep from me
The rest o 'th' island. (as cited in "Shakespeare's Natives")
Looking at the two different colonized characters, we can see an argument that colonization can benefit the colonized; however, it also robs them of anything they owned, such as their land, which is a very savage way for colonialists to behave.