Ukerewe, the island in the Tanzanian half of Lake Victoria where I am currently spending a few months, is famous for witchcraft. Witches are found in every village, in every street. They earn a living by selling curses. If you want to punish a friend or destroy an enemy, you pay a witch to smite him with some misfortune – illness, injury, impoverishment, death. Because these things are so common anyway, it is easy for witches to claim that it was the curse that did the damage, and easy therefore for them to stay in business. And there begins the vicious circle – bad things sustain belief in witchcraft, belief in witchcraft absolves you (or your government) of any responsibility for your lot, so more bad things happen, and the witches grow ever more powerful.