Proaches of Feydh Kashani and Thomas Aquinas inIn this essay, we seek to comparatively study the field of place of reason, revelation and relation of these factors with each other based on a descriptive-analytic method. Feydh Kashani and Thomas Aquinas as two influential Muslim and Christian theologians within the framework of their own religious principles, contrary to the current notion of the theologians, have never denied or reproached or neglected rational knowledge. The understanding of these two theologians of reason seems to have many similarities including deficiency and potentiality of rational knowledge, role of rational knowledge in providing the path for revelation of human natural tendency towards the knowledge of God and reaching divine vision. The present study shows that regardless of the differences that are concerned with the intellectual contexts of these two thinkers, in their ideas, we can see some common notions like significance and limitation of intellection, dependency of rational knowledge on divine mercy and effusion, insistence on the superiority of revealed knowledge over rational knowledge and depiction of end of cordial knowledge based on vision of divine essence. Of course, according to these two thinkers, knowledge alone is never deciding and knowledge along with the promotion of faith that is the result of divine effusion leads to the highest level of faith, i.e. reaching the status of divine purity.