A poem is an act of memory, first forged out of the need to remember what would otherwise be forgotten – in an oral tradition record-keeping is an art, not an act of administration. Early poems were to be recited, memorised, passed on, and a heightened language lifted by rhyme and beat makes the memorising easier.
It remains true, and always will, that a great poem resists being paraphrased, and resists being reduced to a simple narrative argument. It is another litmus test of quality, perhaps, that new meanings can continue to be found in the poem, and that one can go ever deeper without ever feeling one has plumbed the ultimate depths. This is not ambiguity or clarity at issue, therefore: it is richness, and resonance, and a lifetime of memory folded into a small, densely-worded space: in other words, a true poem.
(both links found thanks to Frank Wilson’s Books, Inq.)