Some theological subjects such as faith, determinism vs. free will and pre-eternity vs. Origination of the Quran constitute primary issues of concern and debate among different Islamic sects. It was the Kharitie who discussed the issue of faith for the first time. They considered Umayyad caliphs unbelievers due to the cardinal sins they committed. However, major Islamic sects such as the Ash’arite, shiite and Murjiite considered cardinal sinners as reprobates, not unbelievers. As a philosopher and theologian, sanaei pays due heed to the issues of faith and unbelief amongst other important theological subjects, e.g. monotheism, determinism vs. Free will, pre-eternity vs. Origination of the Quran, and therefore, requires a careful analysis. On the theological side, Sanaei believes that the main pillar of faith is one's true and heart-felt affirmation and acknowledgment; he considers the other two pillars, i.e. corporal practice and verbal confession, of less significance. According to his view, a Muslim will achieve faith as defined by the Quran and tradition by removing the obstacles in its realization, and such faith will bring forth immunity and security in this world and the other. On the mystical side, Sanaei's views on faith and unbelief bear some resemblance to those offered by Eynolghozat, Hussein ibn-e Mansour Hallaj and Imam Muhammad Ghazzali. Here, Sanaei believes that there is no difference between faith and unbelief since the ultimate destination of both is the Beloved. The article will conclude by discussing the main moral virtues which reinforce the spiritual of faith.