It is the crowning virtue of a work of art, as it is of a man, that it should be an example of its own doctrine, an incarnation of its own main symbol. A poem about fire ought to burn. A poem about a brook ought to flow. A poem about childhood ought not just to tell about children but ought to be like a child itself, as are the best of Blake's Songs of Innocence.
Harold C. Goddard, The Meaning of Shakespeare