One of the important studies on religious epistemology is the study of the relativity of religious knowledge; for it requires many serious consequences, such as religious pluralism, Hermeneutics, multi-interpretations, transcendent unity of religions, and other results, in which epistemological approach has turned to another orientation. We have tried to show the foundations and premises on which relativity can be based, focusing on the theses of the German philosopher Immanuel Kant with analyzing and criticizing them. The study has concluded that all the attempts, on which relativism has been based from the analysis of perception according to the Kantian views, or according to materialism or subjective relativity. However, all of this cannot be acceptable; because it brings science out of its and methodology state to its state of generation of perceptions. And this leads to a complete rupture between perception and objective reality of perceived facts. Hence, all the results that have been based on relativity would collapse; for it has been claimed that relativism is not compatible with the denial of realism, but it rather makes each person have a share of the truth.