In the parlance of Islamic studies, the Arabic عقل is oftentimes rendered “reason” or “intellect”. While these translations are not inaccurate, they are however restrictive, as well as being indifferent to the variegated senses in which ʿaql was used and understood by different groups and in different contexts in early Islam.
I can think of at least six different contexts where ʿaql carries meanings not shared with the other.
First, in the context of the Qurʾan. The terms ʿaqalah and yaʿqilu, as cognates of ʿaql, appear over fifty times in the Qurʾan. They are employed as conceptual equals to tafakkur (تفكر) and tadhakkur (تذكر). In the quranic discourse, the term ʿaql, and its conceptual cognates, reflects a plethora of interconnected concepts associated with meditative reflection of the divine and the remembering of godly bounties bestowed on humanity which is in turn closely tied to assent and submission to divine authority (as Amir-Moezzi argued in his Early Divine Guide).
SECOND, in the context of traditional Shiʿism (before the fifth/eleventh century). The opening chapter of the ḥadīth compendium of al-Kāfī, by Muḥammad b. Yaʿqūb al-Kulāynī (d. 329/940), is devoted to ʿaql and jahl, aptly entitled Kitāb al-ʿaql wa-l-jahl (which contains 36 traditions). The traditions cover four interrelated themes and concepts (addressed in detail in the Early Divine Guide).
Theme 1: ʿAql as cosmic morality that guides the faithful in his or her quest to overcome impiety and ignorance. In a tradition attributed to the sixth imam Jaʿfar al-Ṣādiq (d. 148/765), ʿaql is said to consist of 75 traits (described as جنود) that include faith, justice, soft-headedness, knowledge, mercy, restraint, munificence, etc. Each trait (or jund) is contrasted with its opposite (for example, simple-mindedness is contrasted with comprehension).
Theme 2: ʿAql as ethical and epistemological tool that helps the believer arrive at sound judgments and informed decisions. The ethical and epistemological dimension of ʿaql can be developed by studious education, the traditions state, that is rooted in the teachings of the imams.
Theme 3: ʿAql as metaphysical mean to perceive and comprehend the divine. The traditions describe ʿaql as a type of interior vision (بصر) that brings the believer to recognise the “signs of God”.
Theme 4: ʿAql as soteriological dimension that guarantees salvation, conceptually encapsulated by the famous ḥadīth of al-Ṣādiq (responding to the question, “what is ʿaql?”), “It is that by which the Merciful is worshipped and through which Paradise is attained” [العقل ما عبد به الرّحمن و اکتسب به الجنان].
THIRD, in the context of traditional Sunnism. Traditional Sunnism split into two camps over the concept of ʿaql with one camp rejecting the traditions of ʿaql as of dubious attribution, while the other considered a number of these traditions as consisting of sound meaning. Two figures stand out as the salient representatives of the rejectionist camp: Ibn Ḥibbān al-Bustī (d. 354/965), the famous Shāfiʿī traditionist and evaluator of rijāl and Ibn Qayyim al-Jawziyyah (d. 751/1350). In his Rawḍat al-ʿuqalāʾ wa-nuzhat al-fuḍalāʾ, Ibn Ḥibbān writes critically of the purported ʿaql traditions attributed to the Prophet Muḥammad, dismissing them as unsound and lacking in veracity. The lack of scriptural provenance notwithstanding, Ibn Ḥibbān goes on to adumbrate the qualities of the one who possess ʿaql (the opposite of the ignorant, the jāhil), defining the essence of ʿaql as yearning to achieve refined ethical behaviour and to dispel ill-manners.
Similarly, Ibn al-Qayyim, in his al-Manār al-munīf fī l-ṣaḥīḥ wa-l-ḍaʿīf, dismisses all the traditions about ʿaql as fabrications that have no basis in the Sunnah.
Representing the second camp in traditional Sunnism and adopting a less dismissive attitude than those before and after him, was Ibn Abī l-Dunyā (d. 281/894), the famed littérateur and tutor of several ʿAbbasid princes. In his Kitāb al-ʿaql wa-faḍluh, Ibn Abī l-Dunyā records 102 traditions about ʿaql highlighting the ethical dimension of ʿaql as well as its ability to caution against foolhardiness. A few traditions recounted have Shiʿi isnāds, such as the tradition tracing back to the Kufan Shiʿi traditionist Abū Ḥamza al-Thumālī (d. 149/766). For the accommodationist camp among traditional Sunnis, ʿaql is a means to cultivate good ethical conduct and to avoid bad habitual traits.
FOURTH, in the context of major kalām traditions, such as the Muʿtazili, Ashʿari, and rational Shiʿi. Starting with the Muʿtazilis, there was a broad agreement among their early and later proponents that ʿaql (used interchangeably with fikr, contemplative reflection) is an epistemological tool of discovery that precedes the probative authority of scripture (الفكر قبل ورود السمع). In this sense, ʿaql is a means of discovering good and evil (الحسن و القبح), and a tool of reasoning that confirms the existence of the Creator, as explained in detail by the famous Muʿtazili theologian al-Qāḍī ʿAbd al-Jabbār (d. 415/1025) in his Sharḥ al-uṣūl al-khamsah:
For the Ashʿaris, ʿaql is that which leads to discovery of new knowledge after reflective and discursive thinking. The agent possessing ʿaql (العاقل) must distinguish between sound and distorted reflection (النظر). The former is where the conclusion follows necessarily from the premise, while the latter is its opposite. The primary objective of ʿaql is to arrive at the knowledge that the world was created in time, as explained by the renowned Ashʿari theologian Imām al-Ḥaramayn al-Juwaynī (d. 478/1085) in his Kitāb al-irshād:
The rational Shiʿi view of ʿaql is presented by al-Shaykh al-Mufīd (d. 412/1022) in his credal summary Awāʾil al-maqālāt, where he describes ʿaql as a tool of investigation and demonstration that must act in tandem with scripture, and not independently of it. For al-Mufīd, ʿaql is a tool that operates alongside scripture in order to arrive at new knowledge, such as knowledge of God, good and evil, and the necessity of the Imam.
FIFTH, in the context of early Arabic philosophy as exemplified in the peripatetic tradition. In his Risālah fī l-ʿaql (رسالة في العقل), the towering Arabic philosopher Abū Naṣr al-Fārābī (d. 338/950) assigns multiple senses to the intellect (al-ʿaql) following the division found in Aristotle’s De anima, where intellect has the sense of potential, actual, acquired, and active. The potential intellect is the part of the soul that is disposed to abstract quiddities and forms. The active intellect, writes Fārābī, renders the thing that was potential intellect an actual intellect. The acquired intellect is the sense where all or most of intelligible thoughts are known to the agent. The last, namely the active intellect, is the cause of human thought. The active intellect relies on concepts to enable the human intellect to think by abstracting the forms that it emanated into matter.
SIXTH, in the context of Ismaʿili Shiʿism. The Neoplatonic Ismaʿili philosopher and theologian, Nāṣir-i Khusraw (d. 480/1088), in his little-studied Persian work Jāmiʿ al-ḥikmatayn, proffers a definition of ʿaql in line with the teachings of the Shiʿi imams (whom he calls ahl al-taʾyīd), defined here as a simple substance through which human beings form concepts of things. The ʿaql is the guardian of rational soul and that which gives the soul its noble status and possibility of self-awareness. Knowledge, he says, is the activation of the intellect. The intellect is bestowed to humans by God.
This, then, is a brief summary of the main senses in which the term ʿaql was employed and understood in the early centuries of Islam and among different groups, ranging from the traditionalists, theologians, philosophers, and in the text of the Qurʾan. To the best of my knowledge a dedicated monograph that studies and investigates the conceptualisations of ʿaql in early Islam is yet to materialise. There are however a few dedicated studies which deal with ʿaql in specific and restrictive contexts, such as the Arabic philosophical tradition of the peripatetics, but these studies fail to take into account doctrinal developments of the concept and the intra-religious debates surrounding the scope and purview of ʿaql after the move towards canonisation in the third/tenth century.