Caliban is the "monster" from Shakespeare's The Tempest.
In the preface to The Picture of Dorian Gray, Wilde writes:
The nineteenth century dislike of romanticism is the rage of Caliban not seeing his own face in a glass. The moral life of man forms part of the subject-matter of the artist, but the morality of art consists in the perfect use of an imperfect medium.—
Wilde, Oscar. The Picture of Dorian Gray. New York: Dover Publications, 1993. Print.