"Science" is one of the clear and obvious concepts that every person is aware of to some extent. In fact, one of the best blessings of God for mankind is knowledge. Science is a divine gift by means of which God created man, who attained their superior over other creatures and some people over others. Imam Ali, who is himself a divine scholar and the door of Medina of the knowledge as noted by the Prophet, considers knowledge to be the value of a person . To him, in view of that treasure of divine secrets, whoever who has more knowledge and piety has a higher rank. The noble book of Nahj al-Balagha consists of three parts. First, the sermons, then the letters, and then the wisdoms or aphorisms, which are very important due to their generality and adaptability for all generations.
 This article has been written in order to understand "science and its epistemological positions" in the precious words of Imam Ali in Nahj al-Balagha. The result of the investigation and analysis in this article showed that according to Nahj al-Balagha, science and knowledge are not the only criteria of excellence; rather,science combined with righteous action leads to human excellence. Besides science and knowledge have a much higher value than material capitals and serves as the spirit of human sciences, whih has an unlimited capacity for acceptance, and which is aesthetically manifested in the words of the Imam.