eh...I'm tired of the constant arguing that will inevitably show up whenever anything like this is posted. From a practical perspective world peace would be difficult to achieve by any means that wouldn't be considered "insane" simply because people are morons. No matter how philosophically illogical it is to do certain things, people will do em anyway. Heck, people will say one thing and do the exact opposite all the time and not even feel like it's even the slightest bit moronic.
But if we all had modules in our heads that would make such idiocy impossible, and largely control what you can do, then sure there'd be world peace...of course people might be kind of annoyed about that whole lack of freedom deal =P The other method to obtain world peace is simply some crazy country takes over the whole freaking world. It might sound impossible but it's not...it's just that nuclear weapons make it a LOT harder to do without blowing up the whole freaking planet in the process.
Of course that brings me to the final method to obtain world peace. Blowing up the whole freaking planet =P Once we're all dead there will be no more war. SWEET!!!