This appears to be a very complicated world, consisting of all sorts of backgrounds, political considerations, and fundamental philosophical differences, from not only one people to another, but also such varies considerably from country to country, as well as this also being the case within countries, in addition to their communities, of which all of this combined makes for a worldly cacophony. Yet, as messy as that might seen, the fundamental error that mankind makes, and has been making, is to make it their point to concentrate almost exclusively on what they personally desire, or what they believe that they should desire, above all else; and often to the exclusion to the legitimacy of other people and their desires or needs. This thus signifies, that the only possible conceivable way that mankind, in whole, can become united is that each of those that make up the greater family of mankind, must make it their conscious point to desire instead, to collectively to do the will and thereby to be obedient to that which created all of us. That therefore, would serve to slowly but inexorably unite mankind, under one common cause, of which, by doing so, mankind would find itself being more harmonious one to another, and hence on the course to uniting mankind, into that common good.
The bottom line is that it is not possible for mankind to successfully avert wars, disputes, and conflict, unless they are all truly on the same page, of which, therefore, rather than imposing one's will or one's force upon another, they must find themselves bent on accomplishing, instead, to work wholeheartedly for the collective good of the whole. So too, it must be acknowledged that one people can only truly be one, if, in fact, they recognize that there is only one universal truth. After all, if truth is considered to be in the eye of the beholder, then it isn't possible for there to be any solid ground for those that believe such to stand upon, for people's opinions of such are subject to change, as well as being subject to error, and therefore, their concept of truth is by definition, subject to being forever in flux; yet real fundamental truth, by definition, is immutable.
This means that in order for mankind to be one people, they must seek exclusively that one truth. Additionally, that one truth is not going to be some specific dogma, propagated by one specific religion, and thereby dismissive of all else as being wrong or irrelevant, but instead that truth, must be lovingly distilled into its clear and unequivocal prime principle, and none else. So then, this signifies, that the ascent of mankind is based upon not only uniting via common cause in this world, but through the seeking of that one truth; of which, though there are many paths having been so created by mankind's footsteps, each of those paths, will for a certainty, sooner or later lead inexorably to just that one destination, which is that truth.
How long can mankind insist upon having its own way, without understanding that conflict will exist, perpetually through that mindset, because everyone has a different self-will as well as different desires. Instead to be one people, mankind must make it their point to find that union of that one truth, of which, through that common cause and common goal, mankind will thereby truly find peace on earth, and justice for all.