Many spirits are really stupid. To a Christian it seems quite obvious that you cannot fool God, but in many places, fooling superhuman agents is possible and in fact even necessary. In Siberia, for instance, people are careful to use metaphorical language when talking about important matters. This is because nasty spirits often eavesdrop on humans and try to foil their plans. Now spirits, despite their superhuman powers, just cannot understand metaphors. They are powerful but stupid. In many places in Africa it is quite polite when visiting friends or relatives to express one’s sympathy with them for having such “ugly” or “unpleasant” children. The idea is that witches, always on the lookout for nice children to “eat,” will be fooled by this naive stratagem. It is also common in such places to give children names that suggest disgrace or misfortune, for the same reason. In Haiti one of the worries of people who have just lost a relative is that the corpse might be stolen by a witch. To avoid this, people sometimes buried their dead with a length of thread and an eyeless needle. The idea was that witches would find the needle and try to thread it, which would keep them busy for centuries so that they would forget all about the corpse. People can think that supernatural agents have extraordinary powers and yet are rather easily fooled.
Religion Explained: The Evolutionary Origins of Religious Thought
Pascal Boyer