I hold that a long poem does not exist. I maintain that the phrase, "a long poem," is simply a flat contradiction in terms.
I need scarcely observe that a poem deserves its title only inasmuch as it excites, by elevating the soul. The value of the poem is in the ratio of this elevating excitement. But all excitements are, through a psychal necessity, transient. That degree of excitement which would entitle a poem to be so called at all, cannot be sustained throughout a composition of any great length.
The Poetic Principle (1850)