Pragmatism is a method in the new philosophy. According to his theory proving some matters, especially religion, is impossible and thus accepts them considering their application in human’s life. According to the theory of pragmatism all our imaginations, concepts, beliefs and theories are rules for our (pragmatic) “deed”; yet their “reality” lays in their practical benefit for our life. Thus the criterion of reality is beneficence, advantage, and resultant not consistency with the concrete reality. According to the theory of pragmatism, especially from the perspective of William James who is the founder of this school, religion has many personal and psychological benefits such as coherency of personality, vitality, hopefulness, relaxation, psychological health, ... This makes religion functionally necessary for human. I will show the negative results of such a view to religion and being religious. Some of the main criticisms of this method of proving the necessity of religion are: seeing religion as a device, neglecting the main functions of religion, intermixture of religion and religion-like schools, not being universal, not having essential functions, having some substitution for religion’s functions, not distinguishing between reality and function, devotionalism, and etc.