Islam is the religion which guides the humanity not only in every aspect of life, but also solves the problems coming to be faced by humans upto the Day of judgement. On the other side, as the texts of the Holy Quran and Hadith are limited, and the expectedly  coming problems are unlimited, so it is impossible to denote the solution of every problem clearly and vividly in the texts of Holy Quran and Hadith. For this purpose , Quran and Hadith put  some principles explicitly or inexplicitly  through which the solution of every problem may be solved in the light of the Holy Quran and Hadith. This activity is called Ijtihaad and the principles are called Principles of Ijtihaad. The article below is  related to the Principles of Ijtihaad and it consists the explanation and   critical analysis of  the basic principle of Ijtihaad practiced in  Fiqh Ja,fri, that is the authenticity of Wisdom.