Aql is normally translated as “reason” or “intellect”. However, the traditions of the Imams, present Aql as a very different concept. It is a lofty concept that covers a great semantic field. It is both a complex and delicate concept that needs to be understood correctly in the light of the teachings of the Imams (as). It consists of cosmogonic, mystic, and esoteric elements that are mostly non-rational or elements that can be said to transcend the domain of the intellect and rationality.
1. Meaning of Aql before the advent of Islam
Before the advent of Islam, the word Aql merely meant “good sense”. Etymologically, Aql means a hobble – that what was tied to an animal’s feet to restrain it. It’s abstract meaning might thus be said to refer to that faculty that restrains human beings from foolishness. Although the term Aql itself is absent from the Qur’an, the derived form aqala/ya’qilu alone appears over fifty times. From these forms (in the light of hadith) we can understand Aql as a tool for the perception of the divine, simultaneously consisting of a quality of meditative and intuitive reflection. Aql implies a type of deep intuitive knowledge that makes a person assent and submit to divine authority.
2. Aql a gift of Allah (swt)
On the human level, Aql is not just an acquired quality, but a gift from Allah (swt). One might call it an innate faculty of transcendent knowledge, developed to a greater or lesser extent depending on the individual. On this level it is nevertheless different from adab, a good education. “Aql is a favor from Allah (swt)” says Imam Ali Reza, the eight Imam, “whereas good education (adab) is a quality acquired with difficulty. He who works to achieve a good education can succeed, while he who works to attain Aql only increases his ignorance” . Aql cannot be acquired by human effort; man has no control over its presence.
Aql is the “organ” through which the Islamic and Imami doctrine is understood. According to the Imams (as), Aql is the best if not the only way to approach and understand their teachings . Quite often in the speeches of the Imams (as) one encounters expressions like “Aql is the axis of our religion” (al-aql qutb deeninaa), “Aql is the axis around which the truth turns (al-aql huwa l-qutb alladhi alayhi madaar al haqq), “Aql is what one leans upon in our teaching” (al aql huwa ma yuhtajj bihi fi amrinaa). In other words, without Aql the sayings of the Imams (as) remain incompletely understood, ineffective or even incomprehensible.
Another aspect of Aql is illustrated by a dialogue between the sixth Imam (as) and one of his disciples . The latter said, “one man knows the totality of my message after a few phrases; another does not understand me until my explanation is completed; a third after having heard all that I had to say, asks me to explain again”. Imam Jafar (as) responds, “Do you know why that is? It is because the first is he whose embryo was kneaded with his Aql at the time of conception. The second is he whose Aql was instilled at the breast of his mother. The third is he whose Aql was composed in adulthood .
3. Aql is useless without ilm (hadith)
The divine gift of Aql is in a potential state. All man can do is to develop it in order to “actualize” it; it is actualized with the aid of ilm , the initiatory knowledge taught by the Imams (as) in different fashions. “Under the direction of his Aql” says Imam Jafar al-Sadiq (as), “which Allah (swt) has bestowed upon him as a support, an ornament, and a guide to salvation, the possessor of Aql realizes that Allah (swt) is Truth, that Allah (swt) is his Lord, that there are things that Allah (swt) loves and others that He does not love, that both obedience and disobedience toward Allah (swt) exist. He also finds that by Aql alone one cannot grasp (the depth of) all this; that only the sacred Knowledge (ilm) and its development can help man and that without this Knowledge, Aql is of no assistance .
4. Spiritual aspects of Aql
In a long speech addressed to the famous Hisham b. al-Hakam, our seventh Imam, Musa al Kazim (as) outlines the different spiritual aspects of Aql. He discusses almost all Quranic references where the root aqala/ya’qilu appears, and presents Aql as a faculty for apprehending the divine a faculty of metaphysical perception (identified with basar, interior vision), a “light” (nur) located in the heart, and through which one can discern and recognize signs from Allah (swt) .
While the prophets and the imams constitute the “exterior proof” (hujja zahira) of Allah (swt), Aql is the “interior proof” (hujja batina) . The highly spiritual and religious dimension of Aql stands apart from the constant parallels established between the imam (exterior Aql) and the Aql (the interior Imam). Imam Ali al Naqi (as) elevates Aql, in its function of proof, to the same level as the miracles of the prophets (the magical powers of Moses, Jesus’ powers to heal, the power of Muhammad’s words) . “The proof between Allah (swt) and his servants is the Prophet and the Imams (as), and the proof between the servants and Allah (swt) is Aql . It must be added that the very term “hujja” (plural: hujaj) is one of the titles of the Imams (as).
5. No religion without Aql
Aql is a subtle organ of religion, without which man is cut off from his relationship with the divine plan. Without Aql, man is without religion; that is, without that which can “tie” him back to Allah (swt), man forgets his condition as creature and falls into an impious selfishness. It is undoubtedly in this sense that Imam Jafar’s (as) words must be understood: “He who has Aql has a religion, and he who has a religion wins Paradise” .
In the absence of Aql, the “organ” of religion, there can only be false religiousness, an appearance of piety, hypocrisy. When someone mentioned the Aql of a man obsessed by prayers and ablutions, Imam Jafar (as) replied that such a man could not have Aql, since he was obeying Satan . Later, responding to the question “What is Aql?” he said: “That by which the All Merciful is worshipped and through which Paradise is won”. Then he was asked, “Then what was it that Mu’awiya had”? He replied: “It was trickery, a satanic attitude resembling Aql but it was not Aql” .
6. Men will be judged by their Aql
The quality of the religion of each thus depends on the quality of his Aql, which is why it is the criterion by which men will be judged on the day of Judgement. Imam Jafar (as) says “When you hear talk about someone’s religious qualities (husn haal), consider the quality of his Aql (husn ‘aqlihi), for he will be rewarded according to his Aql” . Imam Jafar (as) reports from the Prophet (s): “When you see someone who prays a lot and fasts several times [a year], do not admire him; first consider his Aql” . Imam Al Baqir (as) says: “At the Judgement on the Resurrection Day, Allah (swt) judges His servants according to the degree of Aql that He has given them in this world .
7. Aql as a Cosmic Entity
The Imams (as) defined Aql as the axis of the religion, like an indispensable key opening the mysteries of their teachings and for opening oneself to these teachings.
According to a tradition reported by the fifth and eight imam, Muhammad al Baqir (as) and Ali al Rida (as), when Allah (swt) observes Aql‘s submission and desire for proximity to Him, He will solemnly announce: “By My Glory and My Majesty, I have not created any creature dearer than you, and I offer you in your entirety only to him whom I love. It is taking only you into consideration that I command and that I forbid, that I punish and that I reward” .
In Imamite doctrine the coming of the resurrection is intimately tied to the “Return” of the hidden Imam and to his final mission of definitively conquering the forces of Ignorance; one of the phases of this mission consists in completing and unifying the Aql of the handful of faithful who have resisted this period of spiritual darkness: “At the time of the Return, Allah (swt) will place the hand of our Qaim on the head of the faithful; through this hand, they will have their Aql unified and their hilm completed 
This Aql is thus a cosmic entity, the “Imam” of the forces of Good in perpetual struggle against the forces of Evil directed by Ignorance. It is reflected in man as an intuition of the Sacred, as a light in the heart, making him a soldier of the “imam”, of religion, and thus of Allah (swt); it helps man to fight against the darkness of impious ignorance, and guarantees him salvation. “The beginning of all things”, says Imam Jafar al-Sadiq (as), “their origin, their force and their prosperity, is that Aql without which one can profit from nothing. Allah (swt) created it to adorn His creatures, and as a light for them.
It is through Aql that the servants recognize that Allah (swt) is their creator and that they themselves are created beings, that He is the director and they are the directed, that He is the eternal and they are the ephemeral; they are guided by their Aql when they observe Allah (swt)’s creation, His heavens, His earth, His sun, His moon, His night and His day. It is thanks to Aql that they can distinguish what is beautiful from what is ugly, that they realize that darkness is in ignorance and that light is in Knowledge .
8. Aql as “super-intelligence”
Aql as explained by the Imams (as), could also be translated as a type of “super-intelligence” and as a type of “sacred-intelligence”. For the theologians (including the mujtahids), Aql is the “organ” of the rational, while for the Imams (as) it is the “organ” for perceiving the suprarational (that which transcends rationality). It is also the human counterpart to the cosmic entity – the first entity created by Allah (swt).
The theologians have downgraded and reduced Aql by translating it as “reason”, “rational thinking”, “faculty of intellectual reasoning”, “discernment”, etc. Whereas, the Imams (as) have defined it as superior entity that enables a person to grasp that which transcends rationality. It is through a kind of phenomenon of “resonance”, of mystic synergy, that the “interior imam” (Aql) of the the true Shi’ite (the Momin), recognized and believed in the truth of the words of the Imams (as), regardless of how incredible and non-rational they were. Through the “light” of Aql, the religious consciousness of the Momin not only perceived cosmogonic data, inspired Knowledge, or the miraculous powers of the Imams (as) and other esoteric elements, but this light elevated these elements to the level of articles of faith.
9. Who first corrupted the definition of Aql?
In the Imamite milieu, al Shaykh al Mufid (d. 413/1022) seems to be the first theologian to found his theological argumentation on Aql in its new definition, that is, as intellectual reasoning . He is forced to adapt the definition of the Mu’tazilites in order to be able to confront them in theological polemics . For his disciple al Sharif al Murtadha (d. 436/1044), also a disciple of the famous Mu’tazalite thinker Abd al Jabbar (415/1025), Aql appears to be completely devoid of its early meaning and becomes a synonym of “reasoning” (istidlal)  and “faculty of intellectual speculation” (nazar) .
Limiting Aql to intellectual reasoning is all the more serious, since intellectual reasoning, which exists at a different epistemological, perceptual, and conceptual level, naturally rejects the non-rational; therefore religious consciousness is modified, since intellectual reasoning, can neither perceive nor accept Aql’s intuitive and mystical “resonance” with the “supra-rational”.
Al Mufid criticizes his master Ibn Babuye Shaykh Saduq in the name of reason . Al Sharif al Murtada, even more intransigent, goes so far as to censure al Kulayni and others, accusing them of having introduced into compilations a great number of traditions which appear absurd in the light of reason . Al Shaykh al Tusi (d 460/1067) did likewise in his compilation of traditions about the hidden imam, by saying nothing about all the traditions of esoteric or mystical character, traditions which he knew through one of his own sources, the Kitab al Ghayba written by al Numani Ibn Abi Zaynab (d 345/956). These thinkers neglected the lofty semantic side of the idea, and mistakenly (or purposely) believed they were working in the name of the Aql so lauded by the Imams (as).
The intellectual influence of these early theologians was such that the “rationalist” tendency became, thereafter, the majority and dominant view within the Imamis; this view has existed up to the present day in the name of Usulism. This is how they laid the seeds of corruption in the pure Madhab (deen, religion) as taught by our Imams (as).
10. Usuli Ijtihad based on Aql
The Usuli school is predominantly a “rationalist” school as opposed to a “traditionalist” one. The mujtahid in this school can use reason or rational thinking (which he terms as Aql) to derive/deduce new law. For the Usuli mujtahid, the application of Aql means the application of rational thought or logical reasoning when the revelatory sources (i.e. Quran and Hadith) are silent on a matter.
Aql (reason or human intellect) is one of the four main sources of Islamic law for the followers of the Shi’ite Usuli school. The jurists of the early period, however, did not mention it as a source of the Sharia. The earliest legal work in which Aql is mentioned along with the other three sources is al-Sara’ir by Ibn Idris al-Hilli, although he did not explain what it meant. Those scholars that did explain Aql each described it in a different way. What is now meant by Aql, as a source of the Shari’a, is discovering a law by reasoning using the obvious rules. This involves categorical judgment drawn from both the theoretical and practical intellect. [Ijtihad in Twelver Shi’ism, Esmat al-Sadat Tabatabaei Lotfi]
11. Notes and References:
1. “Al-‘aql hiba’ min Allah wa l-adab kulfa fa-man takallafa l-adab qadara ‘alayhi wa man takallafa l-‘aql lam yazdad bi-dhalik illa jahlan”, al Kulayni, Usul, Vol 1, p. 27
2. Al Kulayni Usul al Kafi vol 1, p 10; Ibn Babuye Illal Sharaa’i, vol 1, pp 88, Ibn Babuye, Amaali, p 418
3. Al Kulayni Usul al Kafi, vol 1, p 30. The disciple in question is Ishaq b Ammar, who knew the teachings of the sixth and seventh Imams.
4. “.. dhaaka man ujinat nutfatuhu bi-aqlih… fa-dhaaka lladhi rukkiba ‘aqluhu fihi fi batn ummih… fa-dhaaka lladhi rukkiba ‘aqluhu fihi ba’da maa kabura…”
5. Al Kulayni, Usul al Kafi, vol 1, p34
6. The expression “recognition of sacred knowledge is made through ‘aql” (ma’arifat al-‘ilm bi-‘aql), al Kulayni Usul al Kafi, vol 1, pg 20, words of the seventh imam, Musa al Kazim; Ibn Babuye, Illal al Sharai, vol 1, p100, Imam Ja’far’s words; Ibn Babuye, Maani al Akhbar, 78, words of the eighth Imam, Ali Ridha.
7. Al Kulayni, Usul al Kafi, vol 1, p 20
8. Sell also al Kulayni, al Rawda min al Kafi, vol 1, p274 and vol 2, p 50; Ibn Babuye, Illal Sharaai, vol 1 pp 98 and 107-108; Ibn Babuye, al Muqni wa-al hidaaya, p 68. This idea takes on a particular importance in the Imamology of early Imamism because it appears to constitute the speculative basis of a spiritual “technique”, perhaps the most important of the early doctrine: that is, the practive of “vision with (or through) the heart” (al-ru’ya bi’l-qalb).
9. Al Kulayni, Usul al Kafi, vol 1, p19
10. Al Kulayni, Usul al Kafi, vol 1, p28
11. Al Kulayni, Usul al Kafi, vol 1, p29
12. “Man kaana ‘aqilan kaana lahu dinun wa man kaana lahu din dakhala l-janna”, Al Kulayni, Usul Vol 1, p12.
13. Al Kulayni, Usul al Kafi, vol 1, p13
14. Al Kulayni, Usul al Kafi, vol 1, p11
15. Al Kulayni, Usul al Kafi, vol 1, p13
16. Al Kulayni, Usul al Kafi, vol 1, p31
17. Al Kulayni, Usul al Kafi, vol 1, p10; and Ibn Babuye, Amaali, 418
18. Al Kulayni, Usul al Kafi, vol 1, p12
19. “Idhaa qaama qaa’imunaa wada’a Allah yaduhu ‘ala ru’uusi l-‘ibaad fa-jama’a bihaa ‘uqulahum wa kamalat bihi ahlamuhum”, Al Kulayni, Usul al Kafi, vol 1, p29; Ibn Babuye, Kamaal al-din, 675.
20. Al Kulayni, Usul al Kafi, vol 1, pp 33-34
21. Al Mufid, al Fusul al-mukhtaara min al-uyun wa l-mahasin
22. The Theology of Shaikh Mufid, Chapters 2, 12 and 17
23. See his “al-Usul al-itiqaadiyya” in Nasfa’is al Makhttaat, ed. Al Yasin, 1954, pg 79
24. Jumal al-‘ilm wa l-‘amal, Najaf, 1967, p. 36 ff.
25. See especially his Sharh ‘aqaa’id al-Saduq, particularly pp. 26f, 46f and 66f.
26. See, for example, his Amaali, Cairo, 1954, p. 81 and especially his Kitab al Shaafi fi l-imaama, the entire introductory section and pp. 98f.