It takes one only one phrase to tell what a Mujtahid is required to do to achieve this goal. That phrase is 'to always maintain justice'. It is very easy to say this phrase but very difficult to practice. First of all it is very difficult to know what is just or unjust, for the learned ones among men have not yet been able to reduce the various definition of justice to a united form. However, Islam has saved us from the confusion in the definition of justice, for Islamic Shari'a has clearly categorized all human activities into five major categories, as it will be mentioned latter, and sanctioned a definite rule for every act.
A just person, according to Islam, is the one who has not violated any of the Islamic orders and prohibitions and does not persist in trivial sins. Since the rule of every act is known in Islam, a Mujtahid does not have to face the difficulties emerging from the confusion in the definition of justice. A Mujtahid's task is to maintain justice in practice throughout his career.
In a religious environment, although it is not easy to maintain justice, but it is not impossible either, for faith and knowledge makes it easier. Thus, we have Mujtahids in every generation who practically do over come all the above mentioned difficulties to achieve the qualifications necessary for a Mujtahid