This article discusses one of the contemporary topics that have been associated with modernity and post-modernity studies. It is the historicism of reason, in light of some viewpoints of Arab modernists who have tried to make use of this Western viewpoint in the Arab and Islamic intellectual arena. That which is meant by the historicism of reason is the changing and altering nature of reason; given that reason is not an absolute or abstract thing secluded outside of time and place, but rather, it is something completely associated with specific conditions and circumstances.The viewpoint undertaken by the followers of historicism of reason is based on a special view to reason, derived from Western thought, and it was set to be applied to language, the Quran, and Arab and Islamic thought. It is also based on a set of epistemological and ontological foundations. Following a descriptive and critical approach, the article discusses this viewpoint, trying to show its defects at both definition and foundations levels.