"World peace" means to me the state of being in which people don't fight; everyone is allowed to live their lives without fear of being killed or deprived of essential resources.
Obstacles:
1.) "Power is of an encroaching nature."--James Madison, Federalist Papers. "Power" in one of its definitions means the will/ability to subjugate others or consolidate groups.
2.) Resources are scarce. There is no such thing as unlimited oil, food, water, shelter, etc.
Both of these concepts go hand in hand with competition. People compete for power and resources, in varying capacities. Competition, though it arguably can lead to peace (perhaps citing capitalist America as a 'peaceful nation' because it fosters an environment in which people are very concerned about their financial security compared to, say, Iraq) is inherently fostered by inequality (economically or otherwise).
Competition is the fundamental law that governs outcomes. In evolution, better adapted organisms competed with and bettered more poorly adapted organisms. In business, better businesses out-compete worse businesses. Better products beat worse products in a consumer marketplace. In a macro sense, "better" people out-compete "worse" people: people that are thin and flexible beat lazy fat people at gymnastics and people that are artistic are better at painting pictures than people with no artistic ability. Savants are better at memorizing things than non-savants. Etc.
I personally do not think "world peace" is a reality, ever. Every human is unique. Every unique human is competing with every other unique human in some capacity, in order to stay on this planet and further proliferate their particular mutations of DNA. Every unique DNA makeup only fosters more DNA mutations, thus, more unique people. Perhaps, at some point, humans will be surpassed by another, more evolved species and the cycle of competition for power/resources will continue. Keep in mind that humans began evolving ~5 million years ago, while the universe has (we think) been around for 14,000 million (14 Billion) years. Humans have evolved from ape-like animals to
Homo sapiens in .036% the amount of time that time has even existed!
Then again, there might be an argument that sometime in the non-foreseeable future, consciousness will evolve in ways commensurate to our ability to conceive of the unknown, ie., the idea of world peace. What I'm trying to say is, perhaps sometime in the future people will rationally be able to restrain themselves from exercising competitive instincts to deprive others of resources, power, etc. Until that day comes, I will make sure I have plenty of food, water and a nice shelter, I am on my cell phone as much as possible, never use my turn signal and crusade around the world forcing people to agree with my religion and beliefs on pain of death (by torture)!
World peace is for sissies.
