Yes. I believe we can. Though not in our lifetime, nor in our children's, nor in our children's children's. I think it will take a catastrophic event, like the quasi-anihilation of humanity, or maybe something like discovering intelligent life beyond our planet. The problem is that the people now in power don't think on a global scale, they are still only thinking not even about the people they lead, but only for themselves, for their own benefit. Thus, outdated concepts like nationalism, racism, sexism, and all other forms of discrimination would have to disappear.

But it doesn't end there. another thing that would have to disappear is religion, There can be no peace while any religion, whatever it may be, still exists. But that's not a bad thing as many religious people would have you believe. To live without belief in the after-life, without belief in a supreme being who created us, that is to live in harmony with humankind, with nature. When all the world will realize that humans, and only humans, can control their own destiny, when we realize that we have no higher authority to answer to but ourselves, when we realize that the Here and Now is more important that the After, when we realize that we alone are responsible for the well-being of our planet's environment and all its life forms, when we realize that humans are inherently GOOD without some sort of indoctrination to turn them evil, then we will live in peace and harmony.

Unfortunately, it ain't gonna happen tomorrow...