Nigeria has not evolved political formulas that explicitly allow religion or religious authorities to define legitimacy. There have, however, been struggles carried out in religious terms over constitutional mechanisms for adjudicating conflict. Religion also has been an element in the conflict between ethnic-language groups. Finally, religion provides a language, a set of values, and institutions through which groups struggle and over which groups contend, both within and between religious communities. It has been necessary for northern leaders to stress Islam in order to maintain northern unity. However, Islam itself has worked to intensify fissures opened up by social and economic change in Nigeria. Islam in Nigeria continues to be contentious in both domestic and foreign policy.