What is a poem?

I have never before read through the Anne of Green Gables series of books. How I missed these, I'll never know, but as I was packing the books (more on this another time) I had this overwhelming desire to read them. I came across this passage today in Anne of Avonlea where Anne and her girlfriends are discussing what poetry is. It seemed too appropriate to pass-up:

"Look, do you see that poem?"[Anne] said suddenly, pointing.

"Where?" Jane and Diana stared, as if expecting to see Runic rhymes on the birch trees.

"There... down in the brook... that old green, mossy log with the water flowing over it in those smooth ripples that look as if they'd been combed, and that single shaft of sunshine falling right athwart it, far down into the pool. Oh, it's the most beautiful poem ever saw."

"I should rather call it a picture, " said Jane. "A poem is lines and verses."

"Oh dear me, no." Anne shook her head with its fluffy wild cherry coronal positively. "The lines and verses are only the outward garments of the poem and are no more really it than your ruffles and flounces are you, Jane. The real poem is the soul within them... and that beautiful bit is the soul of an unwritten poem. It is not every day one sees a soul... even of a poem."

- from Anne of Avonlea by L.M. Montgomery

Interesting Fact: Ms. Montgomery received high praise for her books, and particularly for her title character, from none-other than Mark Twain (one of thousands of adults who read and fell in love with the books initially written for children as a series in a Sunday School magazine). Twain wrote to Ms. Montgomery that she had created "the dearest, and most lovable child in fiction since the immortal Alice."