He loves to lie in the cool slush, like a lias-lizard, shivering with earthy pleasure when his spine is tickled by the small eft-things that course along it, Run in and out each arm, and make him laugh.
The poem is full of these good, close, vivid realisations of the brown prolific earth.
Browning had his own sympathy with Caliban Nor does Shakespeare make him altogether brutish.

He has been so educated by his close contact with nature that his imagination has been kindled.

His very cursing is imaginative: As wicked dew as e'er my mother brushed With raven's feather from unwholesome fen Drop on you both; a south-west blow on you And blister you all o'er.
Stephano and Trinculo, vulgar products of civilisation, could never have said that.

Moreover, Shakespeare's Caliban, like Browning's, has the poetry of the earth-man in him.

When Ariel plays, Trinculo and Stephano think it must be the devil, and Trinculo is afraid: but Caliban loves and enjoys the music for itself: Be not afear'd; the isle is full of noises, Sounds and sweet airs, that give delight and hurt not.
Sometimes a thousand twangling instruments Will hum about mine ears, and sometimes voices That, if I then had waked after long sleep.
Will make me sleep again.
Stephano answers, like a modern millionaire: This will prove a brave kingdom for me, where I shall have my music for nothing.
Browning's Caliban is also something of a poet, and loves the Nature of whom he is a child.