Did the differences between Athens and Sparta lead to the Peloponnesian War?

History shows us that rival powers that are relatively
evenly matched will tend to find reasons to go to war with one another.  They may talk
about things like political views as their causes for going to war, but what is really
going on is that each side simply wants more power.  This is what was going on between
Sparta and Athens in the Peloponnesian War.

There were
clearly differences between Athens and Sparta.  Athens was a mercantile, relatively
democratic state.  Its people were mainly concerned with the good life -- with having
material goods, art, and political rights.  By contrast, Sparta was a "garrison state"
where an elite trained itself for war while subsisting on the labor of a mass of people
who were essentially slaves.

However, this is not what made
the war happen.  The war happened because Athens (after the defeat of the Persians)
tried to expand its power using its naval forces.  This frightened the Spartans -- they
feared that this power might some day be used against them.  This was the true cause of
the war -- Sparta's fear of Athens' power. 

While there
were serious differences between the two poleis, these differences did not really cause
the war.  The war was a struggle for power.