"Genuine poetry communicates before it is understood." --T. S. Elliot
Of course, Elliot was talking about the reader's experience over multiple readings, but that idea is actually embedded in the structure of this Frost poem.
First he gives us an experience; only then, and only slowly, does he tell us what he's talking about.
He doesn't just tell us about the bewilderment. He forces us to become bewildered as well. That way, whether or not the rest of our life experience prepares us to empathize with the characters, we can actually share in this one little aspect of their emotions.
We know what it feels like not to understand. Because we have read this poem.
Not to Keep
by Robert Frost
They sent him back to her. The letter came
Saying. . . . And she could have him. And before
She could be sure there was no hidden ill
Under the formal writing, he was there,
Living. They gave him back to her alive--
How else? They are not known to send the dead.--
And not disfigured visibly. His face?
His hands? She had to look, to look and ask,
"What is it, dear?" And she had given all
And still she had all--they had--they the lucky!
Wasn't she glad now? Everything seemed won,
And all the rest for them permissible ease.
She had to ask, "What was it, dear?"
Yet not enough. A bullet through and through,
High in the breast. Nothing but what good care
And medicine and rest, and you a week,
Can cure me of to go again." The same
Grim giving to do over for them both.
She dared no more than ask him with her eyes
How it was with him for a second trial.
And with his eyes he asked her not to ask.
They had given him back to her, but not to keep.
Julia A. Carney
21 hours ago