 We already saw that the Ikhwân rework the classical heritage in religious terms. They also deal with doctrinal questions linked to religion. Epistle 42 On opinions and religions, the other “programmatic” treatise of the encyclopedia that opens the fourth section, is a discussion of the basic ideas of the Brotherhood such as the multifaceted epistemological problems, the origin of the world, morals and theodicy and the imamate as well as the various doctrines critically considered by the Ikhwân, such as eternalism and dualism. It also develops the apologetic side of Ikhwanian thought.