Literally meaning understanding, perception, sober-mindedness and prudence, as a term, 'aql is a Divine light with which a person can perceive the things that cannot be comprehended with external senses. There have been some who view 'aql as a faculty abstract of matter but which acts in collaboration with matter, or as the "speaking soul," or as the "self" that is identified with the ego. There are others who see it as an important aspect of the speaking soul or self, or a faculty dependent on the spirit. According to many others, 'aql is a Divine immaterial substance or faculty that is separate from the speaking soul and which distinguishes truth from falsehood, good from evil, and what is beautiful from what is ugly.
Another approach is that 'aql (reason), the soul, and the mind are the three denominations of the three functions of the same faculty. From the perspective of its being an immaterial, luminous substance, this faculty is called the 'aql; it is known as the soul in respect of its activities, and as the mind with regard to its perceptions. Although all of these opinions are no more than speculations, it is doubtless that reason ('aql) is one of the most vital faculties of humanity. Even though it cannot be considered an authority—able to give the final judgment concerning good or evil, or what is beautiful or ugly—it nonetheless provides truthful evidence for judging these and similar matters. As it can distinguish between what is beneficial and what is harmful, in many cases, it can also perceive the difference between facts, premises, what is unquestionably true, and theoretical knowledge. So long as it does not remain under the influence of the carnal, evil-commanding soul, it can direct its owner toward reflection, contemplation, and deliberation under the guidance of the heart and spirit and give a push to his/her aspirations for the sublime. The people of God, or saints, tend to call such reason, "the reason of the final destination," or "the reason of the Hereafter," while they describe reason which is completely closed to the sublime as "the reason of the worldly life," or "worldly reason," or "metaphorical reason."
In addition to these denotations, "reason" has been called by different names according to its capacity for perception. They are as follows:
- Reason which understands speech and can distinguish to a certain extent between what is good and beneficial and what is evil and harmful has been called "natural reason." This reason, which is the language of the spirit and the translator of sight and hearing, is held accountable for religious responsibilities.
- Reason which is conscious of itself, perceives the instances of wisdom in and basic purposes for Divine injunctions and prohibitions, evaluating the past and present with their relationships to one another, and which is aware of where its worldly and otherworldly benefits lie has been called "reason of evidence." While "natural reason" is a simple radiance of the spirit, which is found in everyone, this level of the reason is its shining light, and only those who can deeply reflect and contemplate possess it.
- The people of God, or saints, have preferred to call reason which reads the Divine laws of creation and operation in the universe, perceives the essence of the religious sciences, and uninterruptedly advances toward accurate knowledge and knowledge of God by making analyses of all that it reads and reaching syntheses the "reason of experience." The other designations made for this level of reason such as "knowledge," "deliberation," "intellect," and "perception," can be the names given to its different functions.
On whatever level, as a light of Divine Knowledge, reason is a precious substance that is able to perceive—even though limitedly— both itself and all things and events. Furthermore, reason that is able to scan the horizon of the heart and the spirit's observation can benefit from and even share in the gifts that come to them. As for unenlightened reason, which is called "the reason of the worldly life" or "the worldly reason," and which, with its extremely dark horizon, is unaware of the life of the heart and spirit, it is an example of being unfortunate and engulfed in the lowest of the lows.
In turn, reason which has been freed from the influences of carnality and lust and which has gained a certain degree of transcendence is a companion of the heart from a few steps behind, and is favored with the gifts that come to the spiritual intellect. It is through such companionship that reason transcends the earth and the heavens, hastens toward the observation of the mysteries of the universe, and reaches the points where it can hear the breath of the inhabitants of the higher realms. While "worldly reason" sticks fast to the outward appearance of things, "reason of the final destination" or "reason of the Hereafter" travels in the depths of the fields of perception of all inner and outer faculties, getting into the inner dimension of existence and thoroughly studying the apparent causes, shuttling between causes and effects. By solving the cipher of the wisdom in and ultimate purposes for the existence of things and events, it tries to read the Divine purpose for both creation and its existence. It is so active in this endeavor that every day it rediscovers both itself and the whole universe and events, and experiences continuous renewal or revival.
So long as such reason, which has gained luminosity, continues to study the metaphysical realms through the windows of the heart and the spirit, it continuously develops and receives new radiance, and thus acts according to its level of development. As a result, the constant act of turning to the Ultimate Truth causes new doors to be opened unto it, and the gifts that come through these doors encourage it to turn to God more. This profitable trade and interaction on the way toward the Infinite continues ceaselessly.
Indeed, by its very nature, reason is open to the Creator, and it is on a continuous quest for Him. So long as it is not totally overcome by lusts or desires, reason pursues light—and once it has transcended worldliness, it changes into a store of knowledge of God, beginning to live in love and eagerness for Him, and to suck milk from the same breasts as those from which the heart nurses. In respect of the purposes for their creation, the spirit (ruh) is turned toward the Realm of the Transcendental Manifestation of Divine Commands (Malakut) and dreams of the Realm of the Transcendental Manifestation of Divine Attributes and Names (Jabarut); the spiritual intellect (al-latifa ar-Rabbaniya) has eyes turned toward the Realm of the Transcendental Manifestation of Divine Attributes and Names, and aims to be able to be like the secret (sir); and the secret (sir) exists in ecstasies enraptured by the perceptions of the intensity of Divine manifestations and Grandeur. As for reason accompanied by the heart, it is like an observer of the horizon of distinguishing between the reality and spiritual perceptions, which dreams, indeed, can conceive of the stations that are attainable by the spirit, the spiritual intellect, and the secret.
According to Muslim philosophers, reason is a faculty that, in respect of its essential nature, has a connection with the spirit, is open to the horizon of the heart, and diffuses its light by means of the mind. Humans hunt and perceive through it the things that they cannot perceive through the senses. They perceive through it the relationship between cause and effect, and between the one who does something and the thing done. They deduce from the voice the one who speaks; from the scent they detect the flower that produces it; from the footprint they perceive the being who has left it; from the system they decipher the one who has founded it; and from the order they understand the one who has established it. Also, in addition to reason being a faculty which thus perceives the things included in the field of the perception of the external senses, reason is an important element of the spirit that can originate different thoughts and considerations without needing the senses. It sees, reads, makes analyses and syntheses, divides and multiplies, and shuttles between the whole and parts and draws conclusions. Its journeying or making comparisons between two individual things or situations or processes and drawing conclusions is called "analogy"; its making a judgment about the whole based on the information about one or some of its parts, or using known facts to produce general rules, is called "induction." Most scientifically established facts have been concluded through this latter process of reason. There is also another process which is called "deduction," which involves making a judgment about a part based on general information or facts concerning the whole. This third process of reason is an important way to draw final conclusions concerning matters relating to both religious law and the facts of creation and the operation of the universe.
Having comprehended the principle of causality well, reason can collect from God's signs—the facts of the creation and operation of the universe—countless witnesses and proofs for His Existence, His Oneness, and the comprehensiveness of His Mercy by means of the processes mentioned. It can also obtain some clues about its position, responsibility, and final end. However, there are two ways by which reason can get results through these processes. One is that through which reason acts slowly and makes gradual advancement; this is the way of reflection, deliberation, and remembrance, which takes reason a certain period of time. Through the second way, which is called "intuition," reason does not need time and reaches the target in a single attempt. However, intuitive knowledge has also two kinds. One is that which is attained after studies and experiences—it is described as "the intuitive knowledge gained"; while the intuitive knowledge that is reached through the almost instantaneous development of human capacities and special Divine assistance is evaluated as the "product of the sacred power." Every human being is created with a potential for this kind of intuitive knowledge. Those most advanced in receiving the showers of intuition or inspiration are the Prophets, and after them come the ones with sound reason, sound, sincere hearts, and pure spirits.
We should also point out that reason is not always able to find the truth, and thus is exposed or prone to err. Nor is it the inventor of the conclusions it reaches through logic and comparison or the other processes mentioned above. It is an instrument which God Almighty employs as a veil before His acts and something which receives what is sent or given. It is a spiritual mechanism that has been created with the ability to understand Divine address. So long as it is conscious of its true position, reason always stands turned to the Master and never submits to any other than Him. It remains in an interactive relationship with Him and reads existence properly. Changing what it perceives and learns into knowledge of God, reason entrusts this information to the heart and it is always occupied with breathing in and out knowledge and love of God.
Knowledge of God is both a need for reason to satisfy and a source from which it must feed itself. Reason which finds this source can study the creation thoroughly from its simplest level to where it stands, which is regarded as one of the peaks of the highest level of created existence. It feels gratified with the favors reaching it and is jubilant with continuous thanks to God Almighty. When lust, desire, or fantasy and fantastical thoughts cloud its horizon unwillingly, it immediately takes refuge in the pure teachings of God's Messenger, upon him be the most perfect of peace and blessings, and tries to remain as the companion of the heart, following it from a few steps behind, never averting its eyes from the heart's horizon of the observation of the metaphysical realms.
According to the Sufis, as well as being one of the most precious faculties of human beings, reason is paradoxically an instrument which may cause their perdition. In one respect, reason causes humans to rise to an important level above animality and carnality; it whispers to them many things from the perceptions of the heart and spirit that are related to the realms beyond; it acts as both a receptor and transmitter of the most transcendent truths. In return, reason benefits from all the gifts that come to the horizon of the spirit in proportion to the value of the service it renders. Through this service, it becomes priceless and becomes as if the spirit or heart, and is now familiar with the horizon of "the secret." The counterpole of this reason is stupidity, which has no value in God's sight; it is not worthy of His address. Quoting in his Mathnawi the saying of the Prophet, our master, upon him be peace and blessings, "Whoever is stupid, devoid of reason, is our enemy and a bandit waylaying us," Jalalu'd-Din ar-Rumi says, "A person of sound reason is our soul. The breeze blowing from it brings us the scent of sweet basil. Even though it becomes angry and curses me, I do not oppose it. But if a stupid one comes and puts halva in my mouth, I will catch fever from his halva and become ill." On another occasion, he says, "Reason is something luminous which is in search of the truth and desirous of goodness." Ar-Rumi praises reason enlightened with belief as follows: "Believing reason is like a just police officer. It is both the governor and guardian of the city of the heart." Jalalu'd- Din ar-Rumi, the prince of lovers of God, who thinks in this way about reason that has found its way through belief, integrity, straightforwardness, and justice, in turn equates reason which is not turned to God with poisonous insects or vermin, and says, "If your reason hinders you from God's way, it is not reason; it is a snake or scorpion." Sharing the same view, a famous sixteenth-century poet, Fuduli, refers to such corrupt reason as follows:
I ask my reason for guidance;
But my reason shows me to misguidance.
Jalalu'd-Din ar-Rumi uses even harsher language for the misguiding type of reason, saying:
Sell and get rid of that misguiding reason; in its place, buy astonishment and admiration. Such reason is the source of whims and suspicions. Admiration is a different viewpoint. Sacrifice reason for the Prophet Muhammad, upon him be peace and blessings; then say, "God is sufficient for me."
Thus he reproaches the misguiding reason, while welcoming the reason which has been sacrificed for the Prophet Muhammad, upon him be peace and blessings, and which is full of admiration for its Creator.
While some of the Sufis have put forward considerations similar to those of Heraclitus and Anaxagoras concerning the essence, nature, and functions of reason, other Sufis have viewed it as the Divine Being's manifestation at the rank of being known. According to them, it is this stage of creation which is also described as the rank of Divinity, wherein the Divine Attributes and Names have not yet been fully manifested, each according to Its own area of manifestation. This initial manifestation has also been called "the initial identification" or "the initial ability" or "the station of two-bows' length" or "the greatest passage" or "the supreme spirit" or "the initial shadow" or "the truth of Muhammad." Those Sufis have maintained that when, as required by His Essence, God Almighty manifested Himself with His Attributes of Glory from the realm of "the absolute identity," or the realm of "being unidentified and unknown," the "truth of Muhammad" emerged as the essence of the tree of the universe. Some have called this rank of manifestation "the universal intellect," or "the initial speech," or "the initial light." In the view of these Sufis, the whole of creation and all events are a comprehensive mirror formed of the manifestation and development or unfolding of this initial rank.
Some other Sufis, such as Sayyid Sharif, opine that "the first intellect," or the "truth of Muhammad," comprises the truth of the Divine glorious Names and also forms the essence or seed of the universal existence. Some have called it "the soul of unity" with respect to its being the essence or the initial substance of existence, while some others, who consider it from the perspective of its luminosity, describe it as "the first intellect." Nasimi sums up these considerations as follows:
The universal intellect boiled up and the universe came into existence;
The whole universe has been enraptured with the command, "Be!"
Some Sufis regard "the first intellect" as the "Tablet and Pen," which is free of matter and imperceptible. From the viewpoint of its being the first in creation, the essence or truth of Prophet Muhammad, upon him be peace and blessings, is a Pen, while it is a luminous tablet as the essence of the following identifications. Those who have put forward such opinions have tried to reinforce them by basing them on some narrations attributed to our master, upon him be peace and blessings. The Prophetic narrations such as, "The first thing God created was reason (or intellect)," and "The first thing God created was the Pen," and "The first thing God created was my light," have been used by them as the foundations for such considerations.
There have been some who have called the first intellect "the brightest light." This designation seems to be completely proper as it is associated with the initial manifestation of existence from its purely unseen and unidentifiable stage in Knowledge, in the form of the initial identification, and as existence or all things and events are a book readable or an exhibition observable with the light that the first intellect or the essence of the Prophet Muhammad diffuses. Indeed, a book that is unreadable, an exhibition that is unobservable, and treasures that remain hidden cannot be regarded as having existence. So, existence was initially identified and manifested as that pure, brightest light, and after having passed through many stages of identification and manifestation, it emerged as an observable magnificent and perfectly orderly system, which is represented by the universe as the macrocosm and humanity as the microcosm. The light which the Prophet Muhammad, upon him be peace and blessings, brought made the universe a perfect book to be read and a perfect exhibition to be watched or observed.
Upon him be God's blessings and peace to the fullness of the heavens and the earth, and on his Family and Companions altogether.
 Mehmed Fuduli (1490–1556). One of the greatest poets of Turkish classical literature. He lived in Iraq and wrote many works both in verse and in prose. His Diwan ("Collection of Poems") which he wrote both in Turkish, Persian, and Arabic is the most famous among his works. Layla wu Majnun ("Layla and Majnun"), Tarjuma-i Hadith-i Arba'in ("The Translation of the Forty Hadiths"), and Hadiqatu's-Su'ada' ("The Garden of the Holy Ones") are among his most famous works. (Tr.)
 Sayyid Sharif al-Jurjani (1339–1413), was one of the leading theologians of the fifteenth century. He visited Istanbul in 1374, and, upon his return in 1377, he was given a teaching appointment in Shiraz. Sharh al-Mawaqif is his most famous work. (Tr.)
 ad-Daylami, al-Musnad, 1:13; Ibn Hajar, Fathu'l-Bari, 6:289.
 at-Tirmidhi, "Qadar", 17; Abu Dawud, Sunna, 16.
 al-'Ajluni, Kashfu'l-Khafa', 1:311.