To create peace it is necessary to solve the problem of conflict, the problem of social order. A way to solve this problem is private property, but private property by itself cannot guarantee peace. (continued in the next premise)
Common language is the lubricant to easy and manageable trade. Without a common understanding of costs, qualities, and explanation of products, trades are much more difficult to process and accept. It is easier to confuse a transaction or commit deceit when translations are poor due to translators.
Even within one language today we see racism. We also find murder, rape, torture etc. amongst communities who speak the same language. (usa for the racism example or french in regards to former french colonies)
One of the greatest difficulties that mankind faces is the transmission and representation of pain. Without proper techniques and procedures, it is difficult to explain one's pain so that we may feel it. Even within a common language it may be difficult to gauge another person's pain.