What is the main idea and thesis of Chapter 3 of A People's History of the United States?

When thinking
about Chapter 3, the main thing to remember is thatwrites from a Marxist perspective.  This fact
helps us understand the main idea and thesis of this chapter.   In this chapter, Zinn is arguing
that there were serious class divisions in the American colonies.  He argues that the elites
worked to stay on top of the class structure largely by persuading the middle class to side with
them.  They did so by playing on the middle classs fear of the lower classes.

In this chapter, Zinn is arguing that the American colonies had clear class divisions. 
He argues that these class distinctions caused a great deal of conflict.  For example, he says
that Bacons Rebellion in Virginia was caused by a desire for leveling, or creating a more
equal distribution of wealth.  He goes on to say

...levelling was to be behind countless actions of poor whites against the rich in all
the English colonies, in the century and a half before the Revolution.

Zinn then argues that the elites had to fight back against this
desire for leveling.  He argues that the upper classes imposed many laws that were meant to
oppress the lower classes.  He also says that the upper classes enlisted the support of the
middle classes who were afraid of the lower classes.  He argues that there was

a white middle class of small planters, independent farmers, city
artisans, who, given small rewards for joining forces with merchants and planters, would be a
solid buffer against black slaves, frontier Indians, and very poor whites.

In this chapter, then, Zinn is saying that there was a great deal
of class-based conflict in the American colonies and that the elites used a variety of means to
come out on top in that conflict.