Why can't man live peacefully on the earth?

Nations are at war, groups are at war, ideologies are at war with each other, creating conflict. After living for so many centuries, why is it that man cannot live peacefully on this marvelous earth?

Whether it is a world organisation or a particular kind of organisation to bring about peace, such organisations will never succeed because human beings individually, collectively, nationally, are in conflict.

Peace requires a great deal of intelligence, not just demonstrations against a particular form of war or against the nuclear bomb.

There can only be peace when mankind, you and I, have no conflict in ourselves.