The present article is an attempt to study reason or wisdom from the viewpoint of Imam Ali (AS). Therefore the definition, quiddity, essence, and role of reason will be studied from the viewpoint of Imam Ali (AS). Attempts also has been made to study the status and role of reason as well as the signs of reason wisdom and intelligent. Some light will be shed on the relations between reason, religion, knowledge and understanding. What will follow will be the indexes of rationality, rationalism and other aspects of reason. The main hypothesis of this paper is that reason is the surest source of man's knowledge and the best means to verify right from wrong, true from false, good from evil, etc.
Attempts has been made to study the viewpoint of Imam about the role of reason and discuss the issues that are irrational - such as lust, ignorance and carnal self motives -  in his viewpoint.