"Abu Hamid al Ghazali, one of the most famous Muslim intellectuals in the history of Islam, set out to provide a legally sanctioned definition of Unbelief (kufr) as the basis for a criterion for determining who is to be considered a Muslim and who is not, as far as theology is concerned. The translation is preceded by an extensive commentary in which the author reconstructs the historical and theoretical context of the Faysal and discusses its relevance for contemporary thought and practice." This is particularly relevant to the contemporary Muslim theological scene, given the on-going controversy between Revivalist groups, Rationalist and Traditionalist, as to what is the true interpretation of religion and what constitutes a grave deviation from it.