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The tone of the poem "Saddest Poem," which is how the author feels about his subject, is "bereavement;" he is grieving for the loss of his love. And although he says he does not love her, paradoxically, he admits he still does love her: he is enmeshed in the memories of their love together.
I no longer love her, true, but how much I loved her.
Imagery can be found throughout the poem: Neruda, a master of love poetry, also employs beautiful imagery in speaking of the woman he loves. One example deals with the stars. This imagery suggests that their love was beautiful like the stars, and even though the stars are still beautiful, they are now distant and "cold." ("Shiver"could refer to stars twinkling or their temperature, now so much more distant as is his former love). In these lines I believe there is also an inferred metaphor, comparing their love to the stars: all around him are memories of their love, but their love is not there any longer.
The night is full of stars,
and the stars, blue, shiver in the distance.
Another form of imagery, a simile, is found in the line where Neruda compares the poem falling to the dew on the grass—in that the poem falls lightly to the soul, just as dew falls on grass.
And the poem falls to the soul as dew to grass.
We see imagery again as Neruda describes his lover...her body and eyes:
Her voice, her light body. Her infinite eyes.
Finally, the last two lines of the poem seem like a metaphor as well. Neruda compares the last pain she causes him to the last poem he writes for her, extending the comparison to the pain she creates and the love he reveals (in poetry). It is interesting to note, however, that Neruda chooses to use the word "may" twice...as if perhaps there is hope, for she may cause him more pain and/or, he may write more poetry about her, indicating once more the depth of his love for her.
Although this may be the last pain she causes me,
and this may be the last poem I write for her.