War to me is very much like sex. You can develop a theory that says sex is primarily for the exchange of genetic material, or that it's a celebration of life, or you can make up 50,000 theories about why human beings have sex, all of which are in some sense true, all of which by themselves miss the point. Because the answer is extraordinarily complex. It may be for fun, it may be for reproduction, for financial reasons, any number of things.
