In the Preface of The Portrait of Dorian Gray, Oscar Wilde, the writer, uses a metaphor dealing with the Victorians and realism. In particular he quotes Caliban, a Shakespearean ugly monster in the comedy Tempest. In particular, he's unable to see his physicals deformations until he saw his face in a mirror. This made him angry because he didn't want to be ugly, but beautiful. And so the reader sees a desperate situation: this ugly slave who's screaming because hates his physical appearance. 

In Oscar Wilde's Preface, Caliban states for realism, that is his coming in contact with the truth. 

In particular, Victorians are they who are against realism. Indeed they didn't want to see the world as it really was: pathos and grotesque were two techniques, and the characters were all exaggerated. In this way the reality was filtered and the common readers received an alibi for their behaviors and thought to not be like the novel's characters. 

Differently, some sentences after, Caliban states for nineteenth century's aversion to Romantisisms. Indeed this movement contemplates the infinite and one of its features is imagination. Therefore, it represent a reality filtered by the subjects' mind. This appears in the metaphor as Caliban's angry due to his inability to see himself in the mirror. Even if the mirror is empty, he knows his ugliness and can't delete it, he's angry. Therefore, you couldn't change the reality, even you filter it. 

Oscar Wilde answers to Caliban's angry is Aestheticism, so beauty's sake. Instead, Caliban is condemned to suffering, due to his ugliness.