Religious bigotry, and fanaticism. It been the cause of genocide in the past and in the present. It's why the middle east is so unstable and why Israel and Palestine can't reach a peace agreement. It's the theocracy and totalitarianism that threatens our sovereignty. It's the source of thousands of honor killings. It's the root of anti-semitism, the motor for sexism and intolerance, and even in recent years an excuse against fighting climate change. In its most benign forms it takes away a civil liberty or two. In it worst form it kills 4000 people in a matter of minutes. It advocates guilt and fear, teaches close mindedness and the vice of free thought. It's book censoring puritanism. It abuses children and is promotes teaching young minds pseudoscience. In every way it is positively immoral; immoral especially in being completely untrue.

Religious communists like Stalin and Kim Jon Il often get labeled as atheist murderers. It couldn't be further from the truth. Christopher Hitchens is right when he says North Korea is the most religious state on earth at the moment; it's despotism decorated by the belief that the leader is at least semi-divine. Stalin's quest to have "his people" worship (reverence) him (cult head) and communism (doctrine) through statolatry is religion in a purer form than the Vatican could muster, either through its support for fascist and Nazis, or its hangings for heresy, or its belief that condoms are worse than AIDs.

The Greeks were different. Though they mostly believed in gods, they were not religious people at their core. They were materialists like Democritus and Lucretius, with the precursors for todays naturalistic materialism in Epicurus and others. They were open minded, ever tolerant, and discussed avidly and openly without fear of eternal torment or church persecution. Imagine how much farther we would be advanced right now if it wasn't for the great monotheism taking over, virtually stalling the progress Greece made for millennia.

Even war, I firmly believe, has its roots in religious thought. It is true that the Israel, Palestine conflict is one over territory, but the only thing keeping it from resolution is a handful of firm and dogmatic religious Zionists and Arabs who see compromise as blasphemy. These are the things that brew terrorism, and insight empires like America to retaliate in an equally atrocious way. These are the thing that, if dead, would according to Emile Zola "attain perfection" for the word.

Perfection no, but a good start undoubtedly. Religious attitude is the worlds greatest problem, and has been for a long time now.

Dependence of fossil fuels.

Irrespective of CO2 emissions and global warming, our dependence on fossil fuels and their increasing scarcity is likely to be the motivation for the next world war. The increasing demand for energy in China and India will likely bring to a head tensions between first and second world countries. Similarly, if an alternative fuel source is not readily available when fossil fuels are depleted then the world could suffer an economic collapse the likes of which has never been seen before.

I don't think religion is the problem. Religion by itself is a good way to live, but religion, for many people, has become just a tool used to destroy or control others' lives.

The problem is the people who use religion for power.

Take a car, for example. By itself, it's a beautiful and intricate machine that can transport us more quickly than by foot or horses. Put this car into the hands of speed demons and drunk drivers, this car turns into a vehicle of death. Can you really blame the car?

So it's easy to point the finger and blame things for the way things are, but remember all things are arbitrary until we humans decide to use and abuse things for personal gain.

POLAR BEARS!!! and all other bears for that matter!!!

Having fresh drinking water, forget needing food or gas or god, no water for 3 days and you are beyond all of these problems. Desalinization is impractical because of power demands.

If by "world" we mean "the Earth", then the biggest problem of all time will be the eventual destruction of the planet when at the end of its life, our Sun will start to fuse helium into heavier elements and begin to swell up, ultimately growing so large that it will swallow the Earth.

It's being controlled by a small group of elites. They are the puppeteers of humanity.

Division created by cultural, geographic, social, demographic, and religious [etc.] differences.

I think that this is pretty self explanatory.

Division among people is the impetus of conflict in any form. That being said, differences are not bad. By no means should we conform to one ideology, philosophy, or lifestyle, but we should not let our differences separate us and distance ourselves from being beneficent neighbors to everyone we encounter.

While i certainly believe that religious bigotry is a great world problem i think the greatest would be poverty and the lack of compassion to work in a unified unselfish way to bring those in poverty out.

Hearing people say that the poor are poor because its there fault is wrong and just ignorant. there are of course those who have brought themselves to poverty but usually it is society that is at fault.

people in developing countries are born into poverty so how can it be their fault that they are poor?

poverty is caused by many factors and all of them can be reversed if socieiy as a whole commits to them. just a few causes are, corrupt governments(of every type), prices of food, lack of proper health care, lack of education, war,continued inequality, and exploitation of workers.

there is no moral or economical justification for not solving the issue of poverty, yet there is a strong force that exists in the nations that potentially could do the most good, to maintain poverty and prevent a solution from occurring.

i find it frustrating that at least in American politics those who want to solve poverty are often seen as "too liberal" or "leftist" or "elitist" and get no chance to make a serious effort if they want to stay in politics.

those who work to end poverty should be recognized and rewarded for their efforts by others following in their footsteps to solve the worlds greatest problem because until poverty is eliminated their will always be inequality and suffering in this world.

more information about poverty and its causes can be found at

http://www.globalissues.org/TradeRelated/Poverty.asp

The people that inhabit it.

Personally, I lie awake at night hoping that physics doesn't up and change itself on us. See False Vacuum Metastability Event.

Well there are many problems in the world.

I'm gonna go with the one that I feel is the most pressing

and the root behind many of the other problems.

That is... over population.

Being susceptible to big chunks of rock from deep space.