Ijtihad comes from the word “juhud”, which means to struggle, ijtihad means to struggle absolutely to complete a particular task, in the case of Islam, it is the process a mujtihad (scholar) would undertake to apply the established Islamic Principles for a particular situation.
Amongst jurists, there have been many definitions of ijtihad. In the writings of early Shi’ite jurists, the term was usually a pejorative one. The negative implications of the concept are related to the way ijtihad was defined by the major Sunni jurists. Ash-Shafi’i argued that ijtihad and qiyas (analogy) were one in the same, saying “Ijtihad and qiyas are two names with one meaning.” (cf. Muhammad Taqi al-Hakim, الأصول العامة للفقه المقارن, p. 545). Other Sunni scholars, such as Abu Hanifa, generally used the phrase as being synonymous with personal opinion (ra’i), and was regarded as an independent source of Islamic law alongside of the Qur’an , Sunnah, and other sources. Sunni scholars, especially Hanafis, considered ijtihad to be what a scholar does in the absence of evidences, rather than a process applied to those evidences.
Shaykh as-Saduq, speaking of the story of Musa and Khidr, writes:
“Musa, even with the perfection of his intellect, his nobility, and his position with Allah the Exalted, was not able to derive any proofs for the actions performed by Khidr, and he became confused. If the Prophets and Messengers of Allah are not allowed to do analogy or deduction [istidlal] and derivation [[istikhraj]], then most certainly, other people should not be allowed to do so either. If Moses was not given the choice, then how can the Muslim community be given the choice in their Imam? And how can it be appropriate for them to deduce and derive legal rulings with their incomplete intellects, and their conflicting personal opinions?”
أن موسى مع كمال عقله وفضله ومحله من الله تعالى لم يدرك بإستنباطه وإستدلاله معنى أفعال الخضر حتى إشتبه عليه وجه الامر به، فإذات لم يجز لانبياء الله ورسله القياس والاستدلال والاستخراج كان من دونهم من الامم أولى بأن لايجوز لهم ذلك… فإذا لم يصلح موسى للاختيار – مع فضله ومحله – فكيف تصلح الامة لاختيار الامام، وكيف يصلحون لاستنباط الاحكام الشرعية وإستخراجها بعقولهم الناقصة وآرائهم المتفاوتة
Ash-Sharif al-Murtada writes:
“Indeed, ijtihad is invalid (batil). The Shi’a do not allow a person to act on the basis of speculation (zann), opinion (ra’i), or ijtihad.”
إن الاجتهاد باطل، وإن الامامية لا يجوز عندهم العمل بالظن ولا الرأي ولا الاجتهاد “. وكتب في كتابه الفقهي
Shaykh Tusi writes:
As far as analogy (qiyas) and (ijtihad) are concerned, they are not evidences; in fact, Islamic law prohibits the use of them.
إما القياس والاجتهاد فعندنا إنهما ليسا بدليلين، بل محظور في الشريعة إستعماله
Ibn Idris al-Hilli writes:
Analogy (qiyas), istihsan, and ijtihad are invalid (batil) for us.
والقياس والاستحسان والاجتهاد باطل عندنا
One can see from these definitions the way that ijtihad is continuously associated with analogy in particular, which shows the way the meaning of the word had been colored by its use amongst Sunni jurists. However, by the 13th century, the understanding of the word came to change amongst Shi’ite scholars. The idea began to become popular that there is a secondary definition of ijtihad, which does not involve using probabilities, speculation, or analogy. Rather, some scholars began to view it as a process that was applied to religious sources, rather than operating alongside of them as a kind of “back-up” position when evidence could not be found for settling a particular religious question. Historically, this change in the meaning of the word ijtihad is attributed Muhaqqiq al-Hilli (d. 1277), who wrote:
“Ijtihad, as it is commonly understood by the jurists, means expending one’s effort in order to derive legal rulings. Understood in this way, it means to derive the rulings from the legal sources. It rests on speculative understandings that are not normally immediately derivable from the sources themselves. This is true whether or not the evidence is analogy or something else, and so for this reason analogy is a type of ijtihad. Now if it is said: Based on this, then the Shi’a must be people of ijtihad, I would say: Yes, this is the case. However, we must remember that analogy is a type of ijtihad; and so if we exclude analogy, then yes, we are a people of ijtihad, who try to determine legal rulings through various means of reflection, excluding analogy.”
هو في عرف الفقهاء بذل الجهد في إستخراج الأحكام الشرعية و بهذا الإعتبار يكون إستخراج الأحكام من أدلة الشرع إجتهاداً, لانها تبتني على إعتبارات نظرية ليست مستفادة من ظواهر النصوص في الأكثر سواء كان ذلك الدليل قياساً أو غيره, فيكون القياس على هذا التقرير أحد أقسام الإجتهاد. فإن قيل: يلزم على هذا أن يكون الإمامية من أهل الأجتهاد قلنا: الأمر كذلك و لكن فيه أيهام من حيث أن القياس من جملة الإجتهاد فإذا إستثني القياس كنا من أهل الإجتهاد في تحصيل الأحكام بالطرق النظرية التي ليس أحدها القياس
Subsequent definitions of ijtihad would accord with this paradigm. However, there were still disputes about its exact meaning, and it was often associated with obtaining a “probabilistic understanding” (zann/الظن) of religious sources, when a person was unable to come to certainty about a religious ruling. For example, Allamah al-Hilli, the nephew of Muhaqqiq al-Hilli, writes that ijtihad is:
“Expending one’s effort in order to obtain a probabilistic understanding of the religious law.”
إستفراغ الوسع في تحصيل الظن بالحكم الشرعي
A similar definition is offered by Shahid ath-Thani in Al-Ma’alim. Later scholars, like Ayatullah Muhammad Taqi al-Hakim, criticize this type of definition from a number of standpoints (Al-Hakim, الأصول العامة, p. 544):
1) That it does not include knowledge of Islamic laws that are clear and axiomatic, but only encompasses areas of probability and doubt.
2) It does not include religious evidences that do not give probability, and that may be quite dubious in and of themselves, but nonetheless are assigned legal value in Islamic law.
3) It includes types of probabilistic understandings that are not accepted by Islamic law.
As a result, he offers a different definition, one that generally accords with modern Shi’ite jurists understanding of ijtihad:
“An ability to obtain proofs for religious legal rulings, as well as the practical task of obtaining those proofs, either from religious sources, or sources based on natural reason.”
ملكة تحصيل الحجج على الأحكام الشرعية أو الوظائف العملية شرعية أو عقلية
This definition defines ijtihad primarily as a process and an ability that a religious scholar has. In the view of Shi’ite scholars following the usuli school of thought, it is the mechanism by which a scholar seeks to understand religious texts, and to derive rulings based upon those texts. Ijtihad, according to this understanding, must work with the sources rather than parallel to them, and does not constitute an independent juristic source. These scholars would concur with the view of the earlier scholars, that ijtihad in the sense of creating a personal opinion that is relied upon in the absence of religious sources, is impermissible.
The other issue is that in the early times of the shia scholars, including the times of the Imams AS, the rulings available in the hadiths were directly applicable to the time and situations for the people, such that there was no need to derive any new rulings, as the people had already asked the Imams AS all the relevant questions, and the answers were recorded and known to the jurists at the time. As time went on, new situations arose and it was the job of the scholars to apply the known laws to the new situations, this must be done in a sound way, and thus ijtihad was born, different to the Sunni methodology in that there is no use for rai (opinion) or Qiyas (analogy).
Today things are somewhat different, in the Sunni thinking, Ijtihad is still taken to mean to find a ruling when there is not one from the Quran or the Sunnah, the Shia say there is always a principle for the ruling within the Quran and the Sunnah, and its simply a matter of application. (see this article)