Usually we know the obvious cause. The road was slippery, the light was poor. Yet we have driven down this road many times and there has previously been no problem. We drank untreated water, or went to a new restaurant, or were bitten by an insect. Yet at other times we took the same risks and this did not lead to illness. So, very early on in life, we learn to distinguish between the 'how' questions, how something happened, and the 'why' questions.
There is a story of an African who got malaria and went to the doctor, claiming he had been bewitched. The doctor said that malaria was spread by mosquitoes, to which the sick man replied that he knew that, but who had sent the mosquito?
There are two levels of cause, the material one and another which we like to relate to human purpose. When a granary falls and crushes someone among the Azande of North Africa everyone knows that the immediate cause is white ants which have eaten away the wooden pillars. But why was this person walking under it and not another? Who was the witch who turned chance into design.?
Since most things that have happened to us from when we were very young seem to be the result of decisions made by others, it is quite natural that we should believe that the suffering which constantly afflicts us is caused by a human-like force, someone who consciously hurts us in some way. Once we have decided on such a cause we have various choices depending on the culture we live in. They may be evil spirits, ancestors, God or witches.
To choose witchcraft as the explanation, that is the bad intentions of another human being, has a number of advantages. Evil spirits are largely uncontrollable. We are uncomfortable (if we believe in them) to think our ancestors are plotting against us. God is supposed to love and care for us, not kill or maim us. On the other hand, we know many people who are ambivalent towards us. They blow hot and cold. They may secretly be wishing us harm and be able to carry out their intentions because they are witches.
Credit: pagan-magic.blogspot.com