Some African tribes, in particular the Twa and Ewe, create a coherent, cohesive philosophy of mind. There is a shadow that wanders near a grave, or descends into the underground abode of spirits (kuzimu) and soul (Twa called its "edge"), which moves into one of the descendants of the deceased. But this doctrine is not universally perceived consciously and clearly, hence all sorts of uncertainty and conflicting statements. Some Africans believe that in the world of the living are only the spirits of those who died a violent death. Some tribes believe that those who went to the underworld, from time to time back to earth. In Nyasaland it is believed that the spirits for some time after death - a year or two - staying near the graves, and then leave, perhaps to the underworld.