Greed, pride, envy, xenophobia,
and offcourse religion !
Counter culture and the idea of someones elses views penetrating theirs.
?? If I knew the answers....
Too many different personalities.
too many different opinions and stubborness
...because there's too many stubborn as mules people with differing opinions from one another in the world.
If I knew that I would be pretty rich, eh?
because we all aim for the same thing.