The most obvious trend in Yoruba religion is the decline of the traditional cults in the face of Islam and Christianity. This process started early. By the start of the l9th century, Islam had spread widely in areas under Oyo control, and in the 1840s Christianity arrived, brought by the Saro and the missions. The process accelerated with the imposition of colonial rule, and by the 1952 census more than four-fifths of the population of the Yoruba provinces were said to be either Christian or Muslim (Peel, 1967: 294ó5).
Two main aspects of religion will be explored in this chapter: its role as a basis for the formation of social groups, and its role as an ideology and guide to individual action. It is in the first of these that the most obvious changes have taken place. The majority of men and women in many Yoruba towns are now members of Christian or Muslim egbe. At the level of the individual, however, traditional beliefs are more tenacious. For many people, there is nothing inconsistent about combining traditional rites at home with church or mosque attendance, though Christian and Muslim leaders preach against it. The Ifa diviner or babalawo is still an important source of help and advice, though he now shares his clientele with Muslim diviners and Christian Aladura prophets. The dividing line between ‘traditional’ and Christian or Muslim beliefs and practices is often difficult to draw.
In the process of diffusion in Yoruba society, Christianity and Islam have themselves been modified. The new religions share organisational similarities with the old cults, and Yoruba rites of passage have been adapted to fit the new beliefs. At the level of doctrine, both Christianity and Islam emphasise elements which are also important in traditional religion, and there are similarities in the ways in which members of all three religious groups view the supernatural and their relations with it.