Curs’d be I that I did so!  All the charms
     Of Sycorax, toads, beetles, bats, light on you! 
     For I am all the subjects that you have,
     Who 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.

And again, he promises Trinculo his services thus, if he will free him from his drudgery.

     I’ll show thee the best springs; I’ll pluck thee berries,
     I’ll fish for thee, and get thee wood enough. 
     I pr’ythee let me bring thee where crabs grow,
     And I with my long nails will dig thee pig-nuts: 
     Show thee a jay’s nest, and instruct thee how
     To snare the nimble marmozet:  I’ll bring thee
     To clust’ring filberds; and sometimes I’ll get thee
     Young scamels from the rock.

In conducting Stephano and Trinculo to Prospero’s cell, Caliban shows the superiority of natural capacity over greater knowledge and greater folly; and in a former scene, when Ariel frightens them with his music, Caliban to encourage them accounts for it in the eloquent poetry of the senses: 

     Be not afraid, the isle is full of noises,
     Sounds, and sweet airs, that give delight and hurt not. 
     Sometimes a thousand twanging instruments
     Will hum about mine ears, and sometimes voices,
     That if I then had waked after long sleep,
     Would make me sleep again; and then in dreaming,
     The clouds methought would open, and show riches
     Ready to drop upon me:  when I wak’d
     I cried to dream again.

This is not more beautiful than it is true.  The poet here shows us the savage with the simplicity of a child, and makes the strange monster amiable.  Shakespeare had to paint the human animal rude and without choice in its pleasures, but not without the sense of pleasure or some germ of the affections.  Master Barnardine in Measure for Measure, the savage of civilized life, is an admirable philosophical counterpart to Caliban.

Shakespeare has, as it were by design, drawn off from Caliban the elements of whatever is ethereal and refined, to compound them in the unearthly mould of Ariel.  Nothing was ever more finely conceived than this contrast between the material and the spiritual, the gross and delicate.  Ariel is imaginary power, the swiftness of thought personified.  When told to make good speed by Prospero, he says, ’I drink the air before me.’  This is something like Puck’s boast on a similar occasion, ’I’ll put a girdle round about the earth in forty minutes.’  But Ariel differs from Puck in having a fellow-feeling in the interests of those he is employed about.  How exquisite is the following dialogue between him and Prospero!

   Ariel.  Your charm so strongly works ’em,
     That if you now beheld them, your affections
     Would become tender.

   Prospero.  Dost thou think so, spirit?