There are almost as many reasons for war as there have been wars. Here are some examples (excuses for wars) that came to my own mind:ReligionLandInsultRevengeGreed (I want what you have)Desperation (I need what you have)You are different than I amThrowing off oppressionBut there must be a broader, more general common denominator. I'm still thinking.
This needs more consideration than I have time for just at this moment, but my first thought is that you have touched on it yourself in the second from last reason. I think it all boils down to differences, basically different opinions, points of view.
I don't think that differences alone are enough for war. In fact, on your list, I'd thing most of those are excuses for war, not reasons.Take differences. People with difference, even deep and abiding differences, can live together. What makes people fight over that is someone wanting control over one group and villifying the differences between them and another group, ascribing malevolence to those differences. Without someone making those differences into a unifying cause, there is no war.I think it applies to everything but greed. I don't think people start wars to fight oppression. Instead, someone or a group of someones wants power (even if it's just the power to determine their own fates) and uses the oppression of the people to bring them together and start a war - but the impetus is the need for power. Ditto for desperation. People defend themselves in desperation (i.e. someone else started the war), but they don't attack unless someone is bringing them together.In my opinion, war is about the drive for power (a type of greed). It might be directly greed, but money, in that case, is a means of power. That may not mean that drive is inherently evil. Fighting oppression, even if it leads to a group in power, may be a good reason for a war and they might be willing to put something in place for self-governance rather than take the power greedily to themselves. But in the end, what they were fighting for is still power, in this case, over their own destinies.So, short answer: power.
I'm still searching for something more general than these specific reasons for individual wars. I suppose one could get SUPER general and say "man" is the cause of all wars; get rid of man and you get rid of wars. But hopefully there is a reason somewhere in between the specific and the unreasonable.Maybe I should have asked, "What one thing, if we could eliminate it, would remove the cause for ALL wars?"Bear in mind that here we are waxing philosophical and theoretical and perhaps not so practical. Of course, we still need to collect, and make a list of, specific examples of why wars happen if we are to discover a common denominator for why they happen.
@Stephanie Barr - You have some thought-provoking points. For example, I think you are right that a relatively small group of people are actually starting the wars, and not the larger populations. Yet, of course, we in that larger population are "enablers".The thing is, getting the general population organized enough to put their foot down on the special interest groups who instigate wars, itself would require a small group of people with a special interest...
Motivation by a small group of people, even if they have power, doesn't have to lead to war. Note Martin Luther King Jr. and Mahatma Gandhi.But it's hard to find leaders that aren't seduced by the power of leading. It happens, but those that become drunk on power are far more common.
Our own little wars were started for Revenge-with a nice hopeful subtext of Oil. I've not seen the oil and my own desire for revenge ran out long ago. Real War, not just people blowing themselves up in markets, is all about Technology.