Nahj al-Balaghah, which is a case of the manifestation of the deep connection between faith and reason, in many of its propositions, rational explanation and philosophical approach is evident. Assessing the relationship between faith and reason from two dimensions: ontological, epistemological and examining the meaning, angles, origin and interactions of the two using the descriptive-analytical method in Nahj al-Balaghah, is the issue of this research. The findings of the research show that in Nahj al-Balaghah, one part of faith is related to feelings and emotions, one part is related to practical intellect and one another part is related to theoretical intellect, and unlike the Ashchr('39')arites and the Muchr('39')tazilites who viewed respectively faith as only being on theoretical intellect and limited to practical reason, it includes both intellects, and the propositions concerning faith in Nahj al-Balaghah are compatible with rationality, and the prerequisite for believing is rationality. However, the share of practical reason in religious faith is greater.