Note 19 — Chapter VII · THE UTILITY OF RELIGION.
Reading edition
The state of war which normally exists between many, if not most, neighbouring savage tribes, springs in large measure directly from their belief in immortality; since one of the commonest motives to hostility is a desire to appease the angry ghosts of friends who are supposed to have perished by baleful arts of sorcerers in another tribe, and who, if vengeance is not inflicted on their real or imaginary murderers, will wreak their fury on their undutiful fellow-tribesmen.—The Belief in Immortality, Vol. I., p. 468.