An explanation of why there can never be peace, from 'The Parable of the Tribes' by Andrew Bard Schmookler.

"The new human freedom made striving for expansion and power possible.
Such freedom, when multiplied, creates anarchy. The anarchy among
civilized societies meant that the play of power in the system was
uncontrollable. In an anarchic situation like that, no one can choose
that the struggle for power shall cease. But there is one more element
in the picture: no one is free to choose peace, but anyone can impose
upon all the necessity for power. This is the lesson of the parable of
the tribes."
 

The Preacher (Ecclesiastes) is even more succinct:

"Wisdom is better than weapons of war, but one sinner destroyeth much good".