According to fully established hadiths which elucidate the meaning of this saying, knowledge here means the three principles of Islam: unity or tawhid; prophecy or nubuwwat; and eschatology or ma’ad. In addition to these principles, Muslims are expected to acquire knowledge of the subsidiary branches and the details of the injunctions and laws of Islam according to their individual circumstances and needs. It is clear that acquiring knowledge of the principles of religion, even if it be in summary fashion, is possible to a certain extent for everyone. But acquiring detailed knowledge of the injunctions and laws of religion through use of the basic documents of the Book and the Sunnah and technical reasoning based upon them (or what is called demonstrative jurisprudence, fiqh-i istidlali ) is not possible for every Muslim. Only a few persons have the capacity for demonstrative jurisprudence, nor is such acquiring of detailed knowledge required of everyone, for there are no injunctions in Islam requiring one to do what lies beyond his abilities.
Therefore, the study of Islamic injunctions and laws through reasoning has been limited through the principle of "sufficient necessity" (wajib-i kifa’i) to those individuals who have the necessary capability and are worthy of such study. The duty of the rest of the people, according to the general principle of the necessity for the ignorant to depend on the one who knows, is to seek guidance from capable and worthy men of learning, who are called mujtahids and faqihs. This act of following mujtahids is called imitation or taqlid. Of course this imitation differs from imitation in the principles of religious knowledge which is forbidden according to the very text of the Quran, "(O man), follow not that whereof thou hast no knowledge."
It must be known that Shi’ism does not permit imitation of a dead mujtahid. That is to say, a person who does not know the answer to a problem through ijtihad and through religious duty must imitate a living mujtahid and cannot depend on the view of a mujtahid who is not living, unless he had received that guidance while the mujtahid was alive. This practice is one of the factors which have kept Islamic Shi’ite jurisprudence alive and fresh throughout the ages. There are individuals who continuously follow the path of independent judgment, ijtihad, and delve into the problems of jurisprudence from one generation to another.
In Sunnism, as a result of consensus of opinion (ijma’) that occurred in the 4th/10th century, it was decided that submission to one of the four schools (of Abu Hanifah, Ibn Malik, al-Shafi’i, and Ahmad ibn Hanbal) was necessary. Free ijtihad or imitation of a school other than these four (or one or two smaller schools that died out later) was not considered permissible. As a result, their jurisprudence has remained in the same condition as it was about 1100 years ago. In recent times certain individuals in the Sunni world have turned away from this consensus and have begun to exercise free ijtihad.
Hadith in Islam: Sunni and Shia
