Why is unity important in Steinbeck's novel, The Grapes of Wrath?

In John Steinbeck's The Grapes of
Wrath, thousands of people have have lost their jobs, their homes and their
land, and have been forced to pack up and move across the country, looking for work and
a new home where they can begin again.

Ma Joad, the woman
who works extremely hard to keep her family and her extended family healthy, fed and
together, knows how important it is to maintain a sense of
unity.

There are several reasons for this. Being united is
safer: the group is less likely to be harassed/robbed if they stick together. Working
together also increases the chances that the group will survive in terms of finding work
and/or food. Unity is extremely important to provide a sense of belonging that fights
the insidious feelings of alienation brought on by this terrible time in U.S.
history.

In terms of unity, one of the major themes is man
(or the individual) vs society. For instance, when the men try to get work, they are
often competing with others, and "fighting" even those who are hiring, for there are
many man, many hungry families and only a few
jobs.

Commitment is another theme, and this is easier to
apply oneself to if part of a strong collective family-like unit—and that is what the
Joads are. They understand that in order to survive, they must stick together. Those who
do not remain will most likely die. However, there is another side to the question of
commitment: in being devoted to the family, two members of the group are considered
"Christ-like" figures in that they "sacrifice" themselves for the good of
others.

Greater than a commitment to survive is Jim Casy's
sense of obligation to others. To live by his conviction to love everyone, he sacrifices
himself to the authorities so that Tom and Floyd are not arrested. Speaking to Tom of a
sense of his personal duty, Jim says:

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An’ sometimes I love ’em fit to
bust...

Ironically, it seems
that Jim's way of looking at the world (along with his experiences on the road) change
Tom. Formerly a character with no desire to connect with others, he becomes an activist
to fight for the rights of the downtrodden and weak.

Tom is
taking a very dangerous risk in this especially desperate and volatile segment of U.S.
history. The Depression had changed people who can no longer even recognize themselves
as they struggle to find a way to live—for themselves and their family members. When Ma
Joad worries about Tom being killed, he recognizes the possibility, and then delivers
the following famous passage:

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Then I’ll be ever’where—wherever you look.
Wherever there’s a fight so hungry people can eat, I’ll be there. Wherever they’s a cop
beatin’ up a guy, I’ll be there. If Casy knowed, why, I’ll be in the way guys yell when
they’re mad an’ I’ll be in the way kids laugh when they’re hungry an’ they know supper’s
ready. An’ when our folks eat the stuff they raise an’ live in the houses they build—why
I’ll be there.

There is
sadness in that this shows a real possibility of what might happen to Tom as he fights
for social change—for back then, it was a "war," not a discussion.
However, there is also the sense of hope (another theme) that the Joad family and the
entire country will survive these trials, and finally able to care for themselves and
each other as they used to. Unity is what will guarantee this, whether it is that of a
family or that of a group of citizens determined to change the Depression-ravaged world
into a new, better place to live.