Usul al-Fiqh

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Uṣūl al-fiqh or Principles of jurisprudence (Arabic: أصول الفقه) is an Islamic discipline that studies the ways of istinbat or deducing the laws of shari'a, that is, reliable ways of arriving at such laws by an appeal to the traditional evidence (i.e. Qur'an and hadiths) as well as rational evidences.

Shiite Imams (a), especially Imam al-Baqir (a) and Imam al-Sadiq (a), contributed to the origination of usul al-fiqh. They taught the correct methods of deducing the laws of shari'a from the Qur'an and the tradition by encouraging their students to deduce particular conclusions from general principles. Though some problems of usul al-fiqh were raised and discussed during the period of Imam al-Baqir (a) and Imam al-Sadiq (a), and some of their students, such as Hisham b. al-Hakam, had written essays about it, usul al-fiqh as an Islamic discipline discussed by Shiite jurists traces back to the early 4th/10th century and the end of the Minor Occultation of Imam al-Mahdi (a).

Since Sunni jurists did not have the wealth of Ahl al-Bayt's (a) hadiths available to them (because they do not take them as reliable sources of ijtihad), they felt the urgency of having such a discipline much sooner than Shiite jurists, thus they wrote books of usul al-fiqh since early 2nd/8th century. The first Sunni scholar who wrote a book concerning usul al-fiqh was al-Shafi'i under the title al-Risala, and the first Shiite scholars who wrote a book concerning issues of usul al-fiqh were al-Shaykh al-Mufid and al-Sayyid al-Murtada. The latter's best-known book on usul al-fiqh is al-Dhari'a ila usul al-shari'a.


The word "uṣūl" (Arabic: أصول) is the plural form of "aṣl" (Arabic: أصل) which means foundation or principle. The discipline is called so because it provides foundations or principles of jurisprudence and is concerned with proper methods of deducing laws of shari'a from their sources. Since there are different ways to draw upon sources, such as the Qur'an or hadiths, to deduce the laws and thus various ways to understand them, it is necessary to know the rules with which to properly deduce the laws.

Al-Sayyid Muhammad Baqir al-Sadr provides the following definition of usul al-fiqh, "Usul al-fiqh is a discipline discussing the common elements of the process of deducing the laws of shari'a".


Many scholars of usul al-fiqh, or "usulis" as they are usually called, take the subject-matter of usul al-fiqh to be the Four Sources of fiqh, that is, the Qur'an, the tradition (sunna), consensus (ijma'), and reason ('aql). Usul al-fiqh discusses their conditions and reliability.

Al-Akhund al-Khurasani takes the subject-matter of usul al-fiqh to be anything that is central to the problems of usul al-fiqh, whether or not it is one of the Four Sources of fiqh.

Al-Sayyid Muhammad Baqir al-Sadr takes the subject-matter of usul al-fiqh to be the process of deducing the laws of fiqh insofar as its common elements are discussed in usul al-fiqh.


Usul al-fiqh is a discipline that is purely originated from within the Islamic culture. Primarily it was developed within fiqh. Compilation of this science was after the need of the Muslims for principles with which they could deduce their religious obligations. In the lifetime of the Prophet (s), there was not such a need because every new issue would be solved by the Prophet (s). But after the demise of the Prophet Muhammad (s), the unavailability of the Prophet (s) as a source of divine laws, on the one hand, and the expansion of the Islamic territories and the occurrence of several social events, on the other hand, led to some jurisprudential issues in the Islamic community that were not in question before then. Thus Muslims felt the need to deduce the laws of shari'a from the Qur'an and the Prophet (s)'s hadiths and tradition (his words, acts, or consents) in order to find answers to their new questions.

Since Sunni scholars did not have hadiths of Ahl al-Bayt (a) available to them as sources of ijtihad, they felt the urge to form the discipline of usul al-fiqh sooner than Shiite scholars, and they wrote books on usul al-fiqh since the early 2nd/8th century. The first Sunni scholar who wrote a book in usul al-fiqh was al-Shafi'i, under the name of al-Risala. Shiites did not feel this much of urge to ijtihad (deduction of laws from sources) because of the presence of their Infallible Imams (a), but for some reasons, such as the occasional unavailability of their Imams (a) because of their being in other cities or restrictions imposed by caliphs on contacts between the Imams (a) and their followers, they had to deduce specific laws of shari'a from the principles provided by Imams (a).

According to historical evidence, the Imams, particularly Imam al-Baqir (a) and Imam al-Sadiq (a), played a significant role in the formation of usul al-fiqh. They taught the proper method of deducing laws of shari'a from the Qur'an and the tradition to their students by providing them with some principles and encouraging them to make specific conclusions on their basis. According to a hadith from Imam al-Sadiq (a): "We ought to present you with the principles and you ought to arrive at specific conclusions from them." Some companions of the Imams (a) wrote essays and books concerning certain issues of usul al-fiqh. Hisham b. Hakam, a companion of Imam al-Sadiq (a), wrote an essay about "words" or "verbal issues", and then Yunus b. 'Abd al-Rahman, Imam al-Kazim's (a) companion, wrote an essay, Ikhtilaf al-hadith, concerning the contradictions among hadiths, such as the question how to prefer one of the contradicting hadiths to another or how to reconcile them (the so-called problem of "al-ta'adul wa l-tarajih", that is, balance and preference).

Usul al-fiqh was recognized, and compiled, as a separate Islamic discipline by Shiite scholars in the early 4th/10th century—the end of the Minor Occultation of Imam al-Mahdi (a). The first Shiite scholar who wrote such a book was al-Shaykh al-Mufid and then al-Sayyid al-Murtada. The best known work of the latter scholar on usul al-fiqh was al-Dhari'a ila usul al-shari'a. The Shiite version of usul al-fiqh was further developed in the period of al-Shaykh al-Tusi. However, for different reasons, it stagnated after al-Shaykh al-Tusi. But after the efforts made by Ibn Idris al-Hilli, al-Muhaqqiq al-Hilli, al-'Allama al-Hilli and the author of Ma'alim al-din it began to thrive again. In the 11th/17th century, tendencies among some Shiite scholars to Akhbarism, a school of thought developed and propagated by Muhammad Amin Astarabadi, led to another period of stagnation in usul al-fiqh, until after two centuries when "Usulis", under the leadership of al-Wahid al-Bihbahani, could revive usul al-fiqh, and with the emergence of al-Shaykh al-Ansari, it turned into a well-developed, sophisticated discipline.


Here are some scholars who played crucial roles to the main developments of usul al-fiqh:

The most significant Shiite books concerning usul al-fiqh include: al-Dhari'a ila usul al-shari'a, al-'Udda, Qawanin al-usul, Ma'alim al-din, Fara'id al-usul, Kifayat al-usul, and Durus fi 'ilm al-usul. The last three books are still the official textbooks in many Shiite seminary schools.

Issues and Problems

The introduction is concerned with definitions of usul al-fiqh, its subject-matter, the demarcation between sciences, the purpose of usul al-fiqh, as well as the nature of verbal conventions, their signs, issues regarding terms, the problem of whether words of acts of worship only refer only correct acts of act of worship or both correct and incorrect ones (al-sahih wa l-a'amm), the use of a word in more than one meaning, and the problem of mushtaqq (do predicates refer to what has the relevant property at the time of predication or do they also refer to what used to do so as well as what will do so in the future?). Issues discussed in the introduction are not problems of usul al-fiqh; rather they are preliminaries to its issues.

Problems of usul al-fiqh are standardly divided into

  • Verbal issues,
  • Problems of proofs (hujja) and probabilistic evidence (amarat)
  • Practical principles (al-usul al-'amaliyya),
  • Issues of balance and preferences (al-ta'adul wa l-tarajih).

Verbal issues: since the words of the Book (the Qur'an) and the Sunna are sources of jurisprudential rulings, verbal issues are discussed in usul al-fiqh.

Verbal issues include

  • Commands and forbiddances,
  • Implicatures (mafahim),
  • General (al-'amm) and specific (al-khass),
  • Qualified (muqayyad) and unqualified (mutlaq),
  • Iindeterminate (mujmal) and determinate (mubayyan)

Problems of proofs: In the standard division, proofs are discussed after verbal issues. They include issues such as:

  • Reliability of certainty,
  • Probabilistic evidence such as the reliability of al-khabar al-wahid,

Al-Sayyid Muhammad Baqir al-Sadr has presented a different structure of the problems of usul al-fiqh in his Durus fi 'ilm al-usul. He holds that in deducing a law of shari'a, a jurisprudent sometimes finds a reason that shows the real law of shari'a -which is called "proving reasons" (al-adilla al-muhriza)- but he sometimes has access only to some rules that determine the procedural or practical duties. Moreover, al-Sadr maintains that there is a common element among the elements of the deducing the laws of shari'a that is present in both "proving reasons" and practical principles, and that is the "reliability of certainty". Thus al-Sayyid Muhammad Baqir al-Sadr suggests a structure of usul al-fiqh in terms of these three foundations with an epilogue, the reliability of certainty, the proving reasons, the practical principles, balances and preferences (among sources of fiqh).

Significant Problems

Reliability of the Apparent Meanings of the Holy Qur'an

According to the reliability of the apparent meanings (ẓawāḥir) of the Qur'an, the apparent meanings of its words and sentences are reliable as sources for deducing laws of shari'a even if there are no exegetical hadiths confirming the apparent meanings. Though most Muslims have no reservations vis-à-vis the reliability of the apparent meanings of the Qur'an, Akhbaris have appealed to hadiths that prohibit interpreting the Qur'an on one's own opinion to show that the meaning of every verse of the Qur'an should be understood on the basis of a hadith, and it is only the Infallibles (a) who can directly refer to the Qur'an as sources of laws, that is, Akhbaris restrict the understanding of the Qur'an to the Infallibles (a), ruling out the possibility of directly grasping Quranic meanings by others.

Usulis reject this view by an appeal to some hadiths according to which every hadith which is in contradiction with the Qur'an should be dismissed—these hadiths, they argue, authorize everyone to directly refer to the Qur'an as the criterion of the reliability of hadiths. They also appeal to the practice of rational people and some Quranic verses. According to usulis, the verses that ask people to reflect on the Qur'an reveal that it is possible for everyone to reflect on the Qur'an and understand its meanings. Moreover, the practice of rational people shows that Quranic verses can be understood by everyone without the need to referring to hadiths.

The Reliability of the Tradition

The tradition refers to words, acts, and consents of the Prophet (s) or other Infallibles (a). There are two issues regarding the tradition in usul al-fiqh:

  • The reliability of Khabar al-Wahid: Most scholars of usul al-fiqh believe that Khabar al-Wahid, that is, a hadith narrated by one person or few people, is reliable. They appeal to the conditional implicature of the Quranic verse:
"if a wicked person comes to you with any news, ascertain the truth" (49:6)

the verse, they hold, implies that if the person who brings the news is not wicked, that is, if he or she is righteous, then there is no need to ascertain the truth.

  • The problem of contradictions between hadiths: according to most of the scholars of usul al-fiqh, if there are contradicting hadiths, we should first try to reconcile them, and if there is no way to do so, then we should see which one is preferred to the other with respect to its chain of narration, content, acceptance among Muslims or scholars, and the like. And if neither is preferable to the other, then we have the option to act upon whichever we want.

Reliability of Reason

The reason or intellect ('aql) is one of the Four Sources. The theory of the reliability of the reason amounts to the idea that if there is a case in which the reason issues some certain judgment, then that judgment is reliable as a source of deducing laws of shari'a because of its certainty.

Scholars of usul al-fiqh take the reliability of certainty to be essential to it, but Akhbaris deny the reliability of the reason. According to Usulis, the reason is reliable both on rational grounds and the confirmation of shari'a. In other words, since the truth of the principles of the Islamic beliefs is proved by the reason, how can it be unreliable with respect to Islamic laws?

According to scholars of usul, laws of shari'a have their origins in advantages (masalih) and disadvantages (mafasid). Without these underlying advantages and disadvantages, there would be no divine commands and prohibitions. So if the human reason or intellection discovers these advantages and disadvantages by itself, then it can give the same verdict that shari'a would give. This issue is discussed in usul al-fiqh under "mutual entailments of the reason".

Reliability of the Consensus

Scholars of usul al-fiqh discuss the reliability of the ijma' (consensus) and the way laws of shari'a might be deduced thereof. Sunni scholars appeal to a hadith narrated from the Prophet (s) according to which he allegedly said: "my people do not agree over something wrong" to show the reliability of the consensus of Muslims. However, Shiite scholars do not find this hadith reliable, but they take the reliability of the consensus to be grounded in the fact that there are Infallibles (a) among the Muslims. In other words, Shiite scholars do not believe in the reliability of the consensus per se. Rather they take it reliable insofar as it reveals the tradition (words, acts or consents of the Infallibles (a)). That is, if there are no other reasons or pieces of evidence with respect a jurisprudential problem, but we do know that all or most of the companions of the Prophet (s) or Imams (a) have acted with respect to that problem in a certain way, it would then reveal that there was a tradition by Infallibles (a) in this case that we have not received.

Practical Principles

In cases where a jurisprudent has no way to discover a law of shari'a, in order to obviate practical confusion he can determine the jurisprudential duties of people by an appeal to some procedural or practical principles (al-usul al-'amaliyya). There are four such principles:

  • The principle of exemption (asalat al-bara'a): according to this principle, by default, there is no duty or obligation in any case.
  • The principle of caution (asalat al-ihtiyat): if we have indeterminate knowledge (al-'ilm al-ijmali) that there is an obligation in some case, then we should act in a caution way so as to make sure that the obligation is performed.
  • The principle of option (asalat al-takhyir): on this principle, in certain cases, the person has the obligation to perform whichever options he or she prefers.
  • The principle of continuity (asalat al-istishab): on this principle, if there was a law of shari'a regarding a certain case in an earlier time, then that law still obtains without any changes.

There is a procedure that determines which of these principles to appeal to in each case. If a jurisprudent cannot discover a law of shari'a, then he is in either of the following conditions:

  • Doubt with indeterminate knowledge: that is, the jurisprudent is in a condition in which he has some other reasons to believe that the real law of shari'a is one of the two or more alternatives. For example, we indeterminately know that there is a law of shari'a regarding Friday Prayer during the Major Occultation of Imam al-Mahdi (a): either it is an obligation (wajib) or forbidden (haram). However, we do not know which of these laws is the real one. In such a case, if it is possible to act cautiously in a way that guarantees the performance of the real law, then the principle of caution will apply. Otherwise, the principle of option applies.
  • Doubt without indeterminate knowledge (incipient doubt): if the jurisprudent is in an incipient doubt, either he knows that there was an earlier condition in which a certain law of shari'a applied, or not. In the former case, the principle of continuity applies, and in the latter, the principle of exemption applies.

Some Disagreements between Shiite and Sunni Scholars in Usul al-Fiqh

Analogy (Qiyas)

The word "qiyās" (Arabic: قیاس) literally means measurement or comparison. And in the terminology of usul al-fiqh, it is a method of deducing a law of shari'a in which the shari'a is silent over the cause of a law, but the jurisprudent makes a conjecture about its cause and then applies the same law in a case in which the same cause exists. This is also called "qiyās mustanbaṭ al-'illa" (an analogy in which the cause is conjectured).

Most Sunni scholars appeal to all the Four sources to show that the analogy (or qiyas) is reliable, but Shiite scholars have objected to all these grounds. They also appeal to explicit hadiths from their Imams (a) to the effect that it is impermissible to act upon an analogy in which the cause is conjectured.


Consensus (Ijma')obtains when all Muslim scholars or people agree over a law.

For Shiite scholars, the consensus is not reliable in itself, rather it is reliable insofar as it reveals the view of the Infallibles (a), that is when the consensus shows that the Infallibles (a) have the same view. Thus for Shiites the consensus is not an original source of fiqh, rather it is derived from the tradition (words, acts, or consents of the Infallibles (a)). For example, if we know that all Muslims during the period of the Prophet (s) agreed over a particular jurisprudential problem and acted in the same way, then it will reveal that the Prophet (s) himself was the source of their consensus, and so it discovers his view. Or if all companions of an Imam (a) agreed over an issue, then it will reveal that their act is originated in the view of the Imam (a) himself. Thus:

  • For Shiite scholars, only the consensus of scholars or people who were contemporaneous with the Prophet (s) or Imams (a) is considered to be reliable. So if at present all Muslim scholars agree over an issue, it will not constitute a reliable source for the scholars of the next generation.
  • For Shiite scholars, the consensus is not reliable in itself. That is, it is not reliable in that it is an agreement of people over an issue, rather it is reliable insofar as it reveals the views of the Prophet (s) or Imams (a).

However, for Sunni scholars, the consensus is reliable in itself. That is, if Muslim scholars—the so-called "people of solution and contract" (ahl al-hall wa l-'aqd)—agree over an issue at any time, then their view is definitely right. They believe that it is impossible for the whole Islamic nation to be wrong. Thus, their consensus at a given time has the same status as that of divine revelation. Put differently, for Sunni scholars, the whole Islamic nation is equivalent to the Prophet (s) in that whatever laws they unanimously arrive at is as infallible as the divine revelation to the Prophet (s).

Istihsan (Preferences)

The word "istihsan" (Arabic: اِستِحسان) literally means to consider something to be good. In the terminologies of usul al-fiqh, it refers to what a jurisprudent personally finds to be good by consulting his own intellect. Istihsan is taken to be an independent source of fiqh and is not meant to refer to other sources.

  • Shiite scholars: they do not take istihsan to be reliable. They even take the reason to be reliable insofar as it yields certainty with respect to a law of shari'a. However, personal preferences and conjectures are not reliable in themselves.
  • Sunni scholars: among Sunni scholars, Abu Hanifa and Malik consider istihsan as a reliable source of fiqh. But al-Shafi'i rejected istihsan and took it to be a sort of meddling in divine legislative acts.

Al-Masalih al-Mursala (Public Interest)

Al-Masalih al-mursala (public interest) refers to properties and features matching the purposes of the divine law-giver, though there is no specific reason from shari'a for their reliability or unreliability. Public interests are not reliable in themselves.

Some Sunni scholars believe in the reliability of public interests in some cases, but Shiite scholars reject it altogether.

Factivity and Fallibility

The theories of taswib (factivity) and takhti'a (fallibility) are opposing theories regarding a condition in which a mujtahid's efforts in deducing laws of shari'a in a case in which no explicit evidence from shari'a is available to lead to a law other than the one really legislated by God in fact. Shiite and Sunni scholars have different views about this condition:

  • Factivity (taswib): except some explicit cases, the divine legislation is a function of the views of mujtahids, and even if there is, in fact, a law different from the one arrived at by the mujtahid, then that law will change dependently on the mujtahid's fatwa, that is, the real law would then be whatever the mujtahid arrives at. Mu'tazilas and many other Sunni scholars of kalam, such as Abu Yusuf, Muhammad b. al-Hasan al-Shaybani, Ibn Surayj, al-Muzni, Abu l-Hasan al-Ash'ari, al-Baqilani, al-Ghazali and others, are advocates of such a view.
  • Shiite scholars believe infallibility (takhti'a), that is, they hold that there are unchanging laws in fact that a mujtahid might deduce them from sources available to him, or he might fail to arrive at them. In the latter case, the real law does not change by what the mujtahid arrived at. However, Shiites believe that a mujtahid who fails to capture the real law will be excused and even rewarded by God.
  • Some Shiite scholars believe in a third alternative called "al-masliha al-sulukiyya" (procedural advantages).

See Also


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