What is the central idea of "The Spirit Of the Laws" by Montesquieu?

Of course, with a book this big, there are many important
points in this book.  I would say, however, that the most important idea or ideas in
this work is the idea of a limited government that is set up in a way that prevents it
from abusing its citizens.

The ideas of Montesquieu can be
seen quite clearly in the Constitution of the United States.  In The Spirit of
the Laws, he talked about the need for the rights of individuals to be
protected.  He argued that the best way to do this was through a written constitution
that guaranteed these rights.  He also said that a government based on separation of
powers was needed to ensure the rights of the people.