According to C.S. Lewis, “Symbolism exists precisely for the purpose of conveying to the imagination what the intellect is not ready for.”
Herein lies not only the truth about Symbolism in poetry, but the essential nature of art: Art communicates with the imagination/personality/soul/heart in ways that the intellect cannot. This is why meaningful interface with art cannot be based merely on analysis, historical context, or conscious thought. Also, the creation and the release of art live in the same realm; e.g., both the composition and performance of music are dependent on imagination. Granted, technical mastery enables effective work from either side of the equation, but the employment of technique in a creative vacuum is pointless. As the old question goes, if a tree falls in the forest and no one is there to hear it, did it make sound?