The concept of spirituality as opposed to materiality and the material world constitutes the main principle of all revealed and non-revealed religions. True existence is spiritual in all religions. Spirituality means having great faith in the existence of transcendent and supernatural truths, which, in Mulla Sadra’s view, have their origin in the unique existence of Almighty Truth. Such a belief grants a specific color and direction to human behaviors and various angles of life, so that individuals will never consider their own being or that of others and the world to be in vain. Rather, it fills them with a pleasant feeling of satisfaction. This concept is not limited to the holy doctrines of a specific religion in psychology, and it is not opposed in this field, either. Based on the principles of his Transcendent Philosophy regarding psychology and the mutual body-soul relation, Mulla Sadra believes that behaviors, physical acts, sciences, and human awareness exercise a profound influence over the human soul and spirit and finally determine their fate in the process of the trans-substantial motion and becoming. Accordingly, one’s spiritual and inner health depends on their awareness and behavior. The science of psychology, particularly humanistic psychology, greatly emphasizes the critical role of spirituality in organizing individuals’ life, character, and behavior. According to some existentialist psychologists, such as Frankl and Jung, mental or spiritual health comprises one of the important elements of a healthy personality.