" The symbol in a poem does not function the way it does in everyday life. It operates the way a metaphor does, by introducing the possibility of comparison. But unlike a metaphor, the comparison is never completed. There is only the original thing, and the very strong feeling that it is going to transform, as in a metaphor, but without the other, completing term. Ed Hirsch writes in his Poetic Glossary that "in poetry, a symbol offers a surplus of resonance." This surplus is that strong feeling of meaning, implied but ultimately left unspecified and undefined. "

― Matthew Zapruder , Why Poetry