Islam and faith are two Quranic concepts about which various viewpoints have been presented. From Fakhr-e Razi’s viewpoint, faith means genuine acceptance and firm belief based on reason, acceptance of the prophet Muhammad along with whatever he has proposed and also verbal acknowledgement. From Allameh Tabatabai’s viewpoint it has different definitions some of which are related to basic factors of faith and some others are related to components of faith, i.e. believing in God, divine verses, angles, prophets and their successors, the day of judgment and every decree that are presented by divine messengers. In addition to genuine belief, it is known for Allameh Tabatabai that commitment to the practical effects of faith is one of the signs of faith, while Fakhr-e Razi believes that only genuine belief is enough to be a true believer. Fakhr-e Razi has been involved in some inconsistencies regarding elaboration on his viewpoint about meanings of Islam and faith and the connection between them based on which the relation between Islam and faith is sometimes considered as equality and sometimes contradiction. From one perspective, it is known for him that the relationship between Muslim and believer is overall inclusion and from another perspective it is equality.