How does Grapes of Wrath by John Steinbeck have the kind of ending Weldon describes in the quote below? -Identify the "spiritual reassessment...

Ah, AP Lit!  This is a free-response AP Literature prompt,
circa 1996.

The Grapes of
Wrath--perhaps the most unusual ending of any great novel.  First, there's a
series of endings in the novel.  There's Tom's ending, Rose of Sharon's ending,
and--even broader--the family's ending.

Regarding Tom's
ending: Tom Joad decides to become a kind of Christ-figure by taking up the mantle of
Jim Casey (initials "J.C." for "Jesus Christ").  Instead of physically sacrificing
himself for the cause, the way Christ and Jim Casey did, Tom instead decides to become a
spiritual hero (like the Holy Spirit):

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I'll be all around in the dark. I'll be
everywhere. Wherever you can look, wherever there's a fight, so hungry people can eat,
I'll be there. Wherever there's a cop beatin' up a guy, I'll be there. I'll be in the
way guys yell when they're mad. I'll be in the way kids laugh when they're hungry and
they know supper's ready, and when the people are eatin' the stuff they raise and livin'
in the houses they build, I'll be there,
too.

Tom's spiritual
reassessment is to be a kind of secular working-class hero--in spirit form.  Before
this, Tom was reluctant to get involved in labor disputes, but after Casey's death and
his family's exodus, Tom has learned to put others and a higher cause before his own
needs.

Regarding the Rose-a-Sharon ending, Rose likewise
learns to be a mother of the down-trodden.  After her baby is born stillborn, she uses
her milk to feed the starving old man.  As reprehensible and, well, creepy, this might
have been to the earlier, married Rose, the newly spiritual Rose feeds him with her
milk, a symbolic baptism of unconditional love.

Regarding
the family, Ma's spiritual journey is based on survival.  In her "We're the people"
monologue, she echoes the Biblical plight of the Israelites as they fled from
Egypt:

Rich
fellas come up an' they die, an' their kids ain't no good an' they die out. But we keep
a'comin'. We're the people that live. They can't wipe us out; they can't lick us. We'll
go on forever, Pa, 'cause we're the
people.

More, Ma's spiritual
duty is based on humility and suffering; she must suffer all the hardships with a kind
of spiritual adaptability, much like a Darwinian animal.  This spiritual "survival of
the fittest" is her key to keeping the family together.