The word Ijtihad (which comes from the root word jahada[1]) means to tolerate difficulties. It also means strength and ability (from the root word johada[2]). The term used in Islamic legal ruling means; using the utmost scholarly effort in order to derive and attain a legal [Islamic] ruling from resources and their evidence.

Therefore, having an identical opinion and fatwa amongst Mujtahids is contingent upon several things:

1. Usage of identical Ijtihad resources

2. Uniformity in prerequisite resources which Ijtihad is contingent upon

3. Uniformity in comprehension from these Ijtihad resources

4. Uniformity in [accurate] verification and judgment of applicability

Even though in Shia fiqh the resources for Ijtihad (Quran, Sunnah and Reasoning) are the same amongst Mujtahids, and they all recognize these resources as being creditable; nevertheless, in order to comprehend, make use and derive from these resources other information is necessary, such as; Arabic Syntax, knowledge of customary practices during the time of the Masooms (P.B.U.T.), Logic, principals of Islamic jurisprudence, knowledge of the identity and reliability of hadith transmitters[3], solid comprehension and awareness of Quran and Hadith, etc.[4] Every Faqih (legal scholar), in addition to having sufficient knowledge in these fields, must also have a basis in all of the issues relating to these fields so that he can be able to uses these sciences to better understand the resources of Ijtihad. For example, in using a hadith or narration it is possible that one Mujtahid may not recognize the authenticity of a particular hadith based on the accepted values in the science of Rijal and therefore not use that as a basis for certification and attaining an Islamic legal ruling; yet that may be the only hadith available on that particular issue other than that particular hadith. As a result this Faqih can not give a ruling on that issue, while at the same time other legal scholars may recognize that same hadith as being authentic and use it as grounds for attaining an Islamic legal ruling. The analyzing ability and strength is not the same for all Mujtahids, which is why it is possible for Mujtahids to have a different understanding of a hadith or Quranic verse. Also, it is possible for a Mujtahids to recognize a specific thing as being specific to a particular instance or applicability, while another Mujtahids may not share the same view.

Every single one of these scenarios can be the cause of discrepancies between the fatwas of Mujtahids, yet even so, having taken all of this into consideration, the amount of discrepancies and differences in fatwas are not many and are mostly in the details. However in the majority of issues (with respect to the close to 3000 issue which are in the Towzi Ul-Masa'el[5]of Mujtahids) Mujtahids are uniform in fatwa and opinion.