This study re-examines the relationship between philosophical rationality and religious belief in the early formative stages of Islamic philosophy, focusing on the views of al-Kindī and al-Fārābī. The analysis shows that the boundary between philosophical reason and religion was neither fixed nor conceptually coherent at this initial stage; rather, it gradually emerged through engagement with the Greek intellectual heritage. Al-Kindī, adopting a flexible and cautious approach, sought to preserve the possibility of harmony between reason and revelation—an approach that opened an initial path toward their synthesis, though it largely amounted to a provisional management of theoretical tensions and conceptual discontinuities. In contrast, al-Fārābī may be regarded as the theoretical architect of this interaction; through his systematic organization of the sciences, articulation of epistemic hierarchies, and symbolic interpretation of religious teachings, he helped to consolidate the role of religion within practical philosophy. The findings indicate that the interaction between reason and religion in early Islamic philosophy was a developing and transitional process.