When Ibsen said in reply to the critic who would not allow _Peer Gynt_ to be called poetry, that the definition of poetry would have to be changed to take in his poem, he was stating a condition that always takes place when a new poetic masterpiece appears. The conception as to what is poetry always changes, for what moves man in one age does not move him in another. The poets often have to do what Whitman and Wordsworth did, create the tastes by which they are to be enjoyed. We are all aware that in the eighteenth century poetry meant something entirely different from what we believe it to be to-day. Many men were considered poets then whom we do not regard as such. The same is true of poetry in prose. There was hostility to the poetry in the novels of Balzac, Flaubert and Zola, because the public did not want to accept their artistic innovations, their frankness and their views.
Yeats in his essay "What is Popular Poetry" in the _Ideas of Good and Evil_, said that poetry of a very high order, like the _Epipsychidion_, is not popular for it presupposes more than it says. All good poetry, whether springing from a written or an unwritten tradition, is always "strange and obscure, and unreal to all who have not understanding," and suggests remembrance of impossible things, and glimmers with thoughts and images dating back to unknown history.
There is a great deal of literature or poetry which presupposes some culture, and a sensitiveness to beauty, and especially a highly developed intellect. The man with the commonplace mind, even though he be educated and well read, is often unable to appreciate the beauty of poetry in which new and advanced and unpopular ideas are held in solution. The poetry in the work of Whitman and Nietzsche and Ibsen was not felt by people who could not enter into the spirit of their revolt from contemporary morality. The public cannot appreciate the prose poetry of Hearn because of his rich language and aesthetic sensitiveness.
The public can take an interest in the beauty and poetry of ideas it understands, and written in language that it speaks and in images that it uses; but the poet is often at his best an aristocrat in thought and language, and then it takes a well trained individual reader to like him. Poetry is no longer mere folklore or ballads or musical numbers, all of which the public may enjoy.