The aql is a power which examines and distinguishes the good and bad influences coming from the brain, the devil, and the nafs. During this process, if it can choose the good, it is called aql salim. Allahu Taala, by sending Prophets in addition, informed His human creatures about what is good and useful, what is bad and harmful, and that all the desires of the nafs are bad. The aql can discriminate between the desires of the nafs and the things which were stated to be useful by Prophets, and communicate this realization to the heart. If the heart prefers the thoughts which come from the aql, the desires of nafs will not be committed; that is, you will not let your limbs do that action. If one prefers and wishes to do the deeds which are said to be good according to the Ahkam Islamiya, one will attain bliss. The process of preferring and wishing good or evil with the heart is called Kasb. Human limbs of movement are dependent on the brain, and the brain is dependent on the heart. They act compatibly with the orders of the heart. The heart is a centre wherein all the influences coming from the sense organs, the spiritual influence of the soul, the nafs, aql, angels, memory and the devil are accumulated. Therefore, if the heart follows the aql, creation of the nafs will not prevent people from attaining eternal blessings. The heart not being deceived by and not obeying the nafs, is called Jihad Ekber (greatest jihad) against the nafs. Allahu Taala informs us that He will reward, with high degrees in Paradise, those that make jihad. Nafs can be the cause of people achieving the thawab of jihad, and becoming superior to angels.
