A symbol is indeed the only possible expression of some invisible essence, a transparent lamp about a spiritual flame; while allegory is one of many possible representations of an embodied thing, or familiar principle, and belongs to fancy and not to imagination: the one is a revelation, the other an amusement.

I had still the ambition, formed in Sligo in my teens, of living in imitation of Thoreau on Innisfree, a little island in Lough Gill, and when walking through Fleet Street very homesick I heard a little tinkle of water and saw a fountain in a shop window which balanced a little ball upon its jet, and began to remember lake water. From the sudden remembrance came my poem Innisfree.

If what I say resonates with you, it's merely because we're branches of the same tree.

Mysticism has been in the past and probably ever will be one of the great powers of the world, and it is bad scholarship to pretend the contrary. You may argue against it but you should no more treat it with disrespect than a perfectly cultivated writer would treat (say) the Catholic Church or the Church of Luther no matter how much he disliked them.

I believe... that our memories are part of one great memory, the memory of Nature herself.

Before me floats an image, man or shade, / Shade more than man, more image than a shade.

If a poet interprets a poem of his own he limits its suggestibility.