Al Kindi


Arab scholar
Islamic Golden Age


Syrian postage stamp depicting al-Kindi

Full name            Al-Kindi
Birth      c. 801
Death    c. 873
School/tradition               Early Islamic philosophy, Mu'tazili, Peripatetic school, Islamic science
Main interests   Astronomy Mathematics, Medicine, Philosophy, Psychology, Science, Theology

Abū Yūsuf Yaaqūb ibn Ishāq al-Kindī (Arabic: ) (c. 801873 CE), also known to the West by the Latinized version of his name Alkindus, was an Arab polymath:[1] an Islamic philosopher, scientist, astrologer, astronomer, cosmologist, chemist, logician, mathematician, musician, physician, physicist, psychologist, and meteorologist.[2] Al-Kindi was the first of the Muslim Peripatetic philosophers, and is known for his efforts to introduce Greek and Hellenistic philosophy to the Arab world,[3] and as a pioneer in chemistry, cryptography, medicine, music theory, physics, psychology, and the philosophy of science.

Al-Kindi was a descendant of the Kinda tribe. He was born and educated in Kufa, before pursuing further studies in Baghdad. Al-Kindi became a prominent figure in the House of Wisdom, and a number of Abbasid Caliphs appointed him to oversee the translation of Greek scientific and philosophical texts into the Arabic language. This contact_us with "the philosophy of the ancients" (as Greek and Hellenistic philosophy was often referred to by Muslim scholars) had a profound effect on his intellectual development, and lead him to write original treatises on subjects ranging from Islamic ethics and metaphysics to Islamic mathematics and pharmacology.[4][5]

In mathematics, al-Kindi played an important role in introducing Indian numerals to the Islamic and Christian world.[6] He was a pioneer in cryptanalysis and cryptology, and devised new methods of breaking ciphers, including the frequency analysis method.[7] Using his mathematical and medical expertise, he developed a scale to allow doctors to quantify the potency of their medication.[8] He also experimented with music therapy.[9]

The central theme underpinning al-Kindi's philosophical writings is the compatibility between philosophy and other orthodox Islamic sciences, particularly theology. Many of his works deal with subjects that concerned theology, including the nature of God, the soul, and prophetic knowledge.[10] However, despite the important role he played in making philosophy accessible to Muslim intellectuals, his own philosophical output was largely overshadowed by that of al-Farabi and very few of his texts are available for modern scholars to examine. However, he is still considered one of the greatest philosophers of Arab descent, and for this reason is known simply as "The Arab Philosopher".[11]


             1 Life

             2 Accomplishments

o             2.1 Astrology, astronomy, and cosmology
o             2.2 Chemistry and perfumery
o             2.3 Cryptography and mathematics
o             2.4 Environmentalism and meteorology
o             2.5 Medicine
o             2.6 Music theory
o             2.7 Philosophy and logic
o             2.8 Philosophy of science
o             2.9 Physics
o             2.10 Psychology

             3 Philosophical thought

o             3.1 Influences
o             3.2 Metaphysics
o             3.3 Epistemology
o             3.4 The soul and the afterlife
o             3.5 The relationship between revelation and philosophy
o             3.6 Controversies

             4 Works translated into English

             5 Notes

             6 References



Portrait of Al-Kindi

Al-Kindi was born in Kufa, Iraq to an aristocratic Kindah family, which had migrated there from Yemen. His full name was, in transliteration: Abū-Yūsuf Yaqūb ibn Isāq ibn as-abbā ibn Omrān ibn Ismaīl al-Kindī; (in Arabic: ). His father was the governor of Kufa, and al-Kindi received his preliminary education there. He later completed his studies in Baghdad, where he was patronized by the Abbasid Caliphs al-Ma'mun and al-Mu'tasim. Because of his learning and aptitude for study, al-Ma'mun appointed him to House of Wisdom in Baghdad, a recently established centre for the translation of philosophical and scientific texts. He was well known for his beautiful calligraphy, and at one point was employed as a calligrapher by al-Mutawakkil.[12]

When al-Ma'mun died, his brother, al-Mu'tasim became Caliph. Al-Kindi's position was enhanced under al-Mu'tasim, who appointed him as a tutor to his son. But on the accession of al-Wathiq, and especially of al-Mutawakkil, al-Kindi's star waned. There are various theories why this happened: some attribute al-Kindi's downfall to scholarly rivalries at the House of Wisdom; others refer to al-Mutawakkils often violent persecution of unorthodox Muslims (as well as of non-Muslims); at one point al-Kindi was beaten and his library temporarily confiscated. Al-Kindi died in Baghdad in 873, during the reign of Al-Mu'tamid, "a lonely man".[11]

After his death, al-Kindi's philosophical works quickly fell into obscurity and many of them were lost even to later Islamic scholars and historians. This may have occurred for a number of reasons. Aside from the militant orthodoxy of al-Mutawakkil, the Mongols destroyed countless libraries during their invasion. However, the most probable cause was that his writings never found popularity among influential philosophers such as al-Farabi and Avicenna, who ultimately overshadowed him.[13]


Al-Kindi was a master of many different areas of thought. Although he would eventually be eclipsed by names such as al-Farabi and Avicenna, he was held to be one of the greatest Islamic philosophers of his time. The historian Ibn al-Nadim (d. 955), described him as:[14]

The best man of his time, unique in his knowledge of all the ancient sciences. He is called the Philosopher of the Arabs. His books deal with different sciences, such as logic, philosophy, geometry, arithmetic, astronomy etc. We have connected him with the natural philosophers because of his prominence in Science.

The Italian Renaissance scholar Geralomo Cardano (15011575) considered him one of the twelve greatest minds of the Middle Ages.[15] According to Ibn al-Nadim, al-Kindi wrote at least two hundred and sixty books, contributing heavily to geometry (thirty-two books), medicine and philosophy (twenty-two books each), logic (nine books), and physics (twelve books).[16] His influence in the fields of physics, mathematics, medicine, philosophy and music were far-reaching and lasted for several centuries. Although most of his books have been lost over the centuries, a few have survived in the form of Latin translations by Gerard of Cremona, and others have been rediscovered in Arabic manuscripts; most importantly, twenty-four of his lost works were located in the mid-twentieth century in a Turkish library.[17] The Theology of Aristotle, a paraphrase of parts of Plotinus' Six Enneads along with Porphyry's commentary, seems to have been edited by Al-Kindi.[18]

Astrology, astronomy, and cosmology

In astrology and astronomy, al-Kindi followed Ptolemy's view of the solar system with the Earth at the centre of a series of concentric spheres, in which the known heavenly bodies (the Moon, Mercury, Venus, the Sun, Mars, Jupiter, and the stars) are embedded. In one of his treatises on the subject, he says that these bodies are rational entities, whose circular motion is in obedience to and worship of God. Their role, al-Kindi believes, is to act as instruments for divine providence. He furnishes empirical evidence as proof for this assertion: different seasons are marked by particular arrangements of the planets and stars (most notably the sun), and (according to al-Kindi) the appearance and manner of people varies according to the arrangement of heavenly bodies situated above their homeland.[19]

Al-Kindi discussed the process by which the heavenly bodies affect the material world. One theory he posits in his works is from Aristotle, who conceived that the movement of these bodies causes friction in the sub-lunar region, which stirs up the primary elements of earth, fire, air and water, and these combine to produce everything in the material world. An alternative view found in his treatise On Rays is that the planets exercise their influence in straight lines. In each of these, he presents two fundamentally different views of physical interaction; action by contact_us and action at a distance. This dichotomy is duplicated in his writings on optics.[20]

In cosmology, al-Kindi maintained the traditional Aristotelian view of gravity according to which heavy bodies, such as the Earth, move downward toward the centre and light bodies, such as Fire, move upward away from the centre.[21]

Chemistry and perfumery

As an advanced chemist, al-Kindi was the first to oppose the practice of alchemy; he debunked the myth that simple, base metals could be transformed into precious metals such as gold or silver.[22] He wrote two treatises on the refutation of alchemy: Warning against the Deceptions of the Alchemists and Refutation of the Claim of Those Who Claim the Artificial Fabrication of Gold and Silver.[23]

Building on the work of Jabir ibn Hayyan (Geber), the isolation of ethanol (alcohol) as a relatively pure compound was first achieved by al-Kindi. He was the first to unambiguously describe the production of pure distilled alcohol from the distillation of wine.[24]

Al-Kindi invented a wide variety of scent and perfume products, and is considered the father of the perfume industry. He carried out extensive research and experiments in combining various plants and other sources to produce a variety of scent products. He elaborated a vast number of recipes for a wide range of perfumes, cosmetics and pharmaceuticals. His work in the laboratory is reported by a witness who said, "I received the following description, or recipe, from Abu Yusuf Ya'qub b. Ishaq al-Kindi, and I saw him making it and giving it an addition in my presence". The writer goes on in the same section to speak of the preparation of a perfume called ghaliya, which contained musk, amber and other ingredients, and reveals a long list of technical names of drugs and apparatus.[2]

The Kitab Kimiya' al-'Itr (Book of the Chemistry of Perfume) written by al-Kindi contains recipes for fragrant oils, salves, aromatic waters, and substitutes or imitations of costly drugs. He also provided the earliest recipe for the production of camphor.[2]


The first page of al-Kindi's manuscript On Deciphering Cryptographic Messages, containing the oldest known description of cryptanalysis by frequency analysis.

Cryptography and mathematics

Al-Kindi was a pioneer in cryptography, especially cryptanalysis. He gave the first known recorded explanation of cryptanalysis in A Manuscript on Deciphering Cryptographic Messages. In particular, he is credited with developing the frequency analysis method whereby variations in the frequency of the occurrence of letters could be analyzed and exploited to break ciphers (i.e. cryptanalysis by frequency analysis).[25] This was detailed in a text recently rediscovered in the Ottoman archives in Istanbul, A Manuscript on Deciphering Cryptographic Messages, which also covers methods of cryptanalysis, encipherments, cryptanalysis of certain encipherments, and statistical analysis of letters and letter combinations in Arabic.[26] Al-Kindi also had knowledge of polyalphabetic ciphers centuries before Leon Battista Alberti. Al-Kindi's book also introduced the classification of ciphers, developed Arabic phonetics and syntax, and described the use of several statistical techniques for cryptoanalysis. This book apparently antedates other cryptology references by several centuries, and it also predates writings on probability and statistics by Pascal and Fermat by nearly eight centuries.[27]

Al-Kindi authored works on a number of other important mathematical subjects, including arithmetic, geometry, the Indian numbers, the harmony of numbers, lines and multiplication with numbers, relative quantities, measuring proportion and time, and numerical procedures and cancellation.[28] He also wrote four volumes, On the Use of the Indian Numerals (Ketab fi Isti'mal al-'Adad al-Hindi) which contributed greatly to diffusion of the Indian system of numeration in the Middle East and the West. In geometry, among other works, he wrote on the theory of parallels. Also related to geometry were two works on optics. One of the ways in which he made use of mathematics as a philosopher was to attempt to disprove the eternity of the world by demonstrating that actual infinity is a mathematical and logical absurdity.[29]

Environmentalism and meteorology

The earliest known work concerned with environmentalism and pollution was an Arabic medical treatise written by al-Kindi. His writings, along with the works of his successors (Qusta ibn Luqa, Muhammad ibn Zakarīya Rāzi, Ibn Al-Jazzar, al-Tamimi, al-Masihi, Avicenna, Ali ibn Ridwan, Ibn Jumay, Isaac Israeli ben Solomon, Abd-el-latif, Ibn al-Quff and Ibn al-Nafis), covered a number of subjects related to pollution such as air contamination, water contamination, soil contamination, solid waste mishandling, and environmental assessments of certain localities.[30]

Al-Kindi wrote a treatise on meteorology entitled Risala fi l-Illa al-Failali l-Madd wa l-Fazr (Treatise on the Efficient Cause of the Flow and Ebb), in which he presents an argument on tides which "depends on the changes which take place in bodies owing to the rise and fall of temperature."[2] He describes the following clear and precise laboratory experiment in order to prove his argument:[23]

One can also observe by the senses... how in consequence of extreme cold air changes into water. To do this, one takes a glass bottle, fills it completely with snow, and closes its end carefully. Then one determines its weight by weighing. One places it in a container... which has previously been weighed. On the surface of the bottle the air changes into water, and appears upon it like the drops on large porous pitchers, so that a considerable amount of water gradually collects inside the container. One then weighs the bottle, the water and the container, and finds their weight greater than previously, which proves the change. [...] Some foolish persons are of opinion that the snow exudes through the glass. This is impossible. There is no process by which water or snow can be made to pass through glass.[2]


There are more than thirty treatises attributed to al-Kindi in the field of medicine, in which he was partly influenced by the ideas of Galen,[31] and partly by his own personal experience and other Muslim physicians in his time.

Al-Kindi's most important work in this field is probably De Gradibus, in which he demonstrates the application of mathematics and quantification to medicine, particularly in the field of pharmacology. For example, he developed a mathematical scale to quantify the strength of a drug and a system, based the phases of the Moon, that would allow a doctor to determine in advance the most critical days of a patient's illness.[32]

In his Treatise on Diseases Caused by Phlegm, he provided the first scientific explanation and treatment for epilepsy:[33]

When the phlegm melts and changes to a bad irritant quality, it goes forth and ascends to the brain from a certain direction, then it sinks down through the principal veins towards the heart, and by its irritant quality it deranges the place of sense, thought and recollection in the brain. It passes through the veins towards the heart, and if the natural heat whose source is the heart is strong enough to dissolve it, it does so, and what happens as a consequence is epilepsy (sar). For the parts of the brain which we have mentioned, becoming injured, are overcome and cease to function. The disturbance which we see in the (patients) body is owing to the conflict of the natural (heat) with the affection. When it prevails over it, it attacks and dissolves it. This is the meaning of the foam which is seen at the (patients) mouth. When this occurs, his recovery is near.

In his Aqrabadhin (Medical Formulary), he describes many pharmaceutical preparations, including simple drugs derived mostly from botanical sources as well as animal and mineral sources.[34]

The Kitab Kimiya' al-'Itr (Book of the Chemistry of Perfume) written by al-Kindi contains recipes for salves and substitutes or imitations of costly drugs.[2]

Music theory

Al-Kindi was the first great theoretician of music in the Arab-Islamic world. He proposed adding a fifth string to the 'ud and discussed the cosmological connotations of music. He surpassed the achievement of the Greek musicians in using the alphabetical annotation for one eighth. He published fifteen treatises on music theory, but only five have survived. In one of his treaties the word musiqia was used for the first time in Arabic, which today means music in Arabic, Persian, Turkish, English and several other languages in the Islamic world.[9]

Philosophy and logic

His greatest contribution to the development of early Islamic philosophy was his efforts to make Greek and Hellenistic thought both accessible and acceptable to a Muslim audience. Al-Kindi carried out this mission from the House of Wisdom, an institute of translation and learning patronized by the Abbasid Caliphs, in Baghdad.[11] As well as translating many important texts, much of what was to become standard Arabic philosophical vocabulary originated with al-Kindi; indeed, if it had not been for him, the work of philosophers like Al-Farabi, Avicenna, and al-Ghazali might not have been possible.[35]

In his writings, one of al-Kindi's central concerns was to demonstrate the compatibility between philosophy and natural theology on the one hand, and revealed or speculative theology on the other (though in fact he rejected speculative theology). Despite this, he did make clear that he believed revelation was a superior source of knowledge to reason because it guaranteed matters of faith that reason could not uncover. While his philosophical approach was not always original, and was even considered clumsy by later thinkers, he successfully incorporated Aristotelian and neo-Platonist thought into an Islamic philosophical framework. This was an important factor in the introduction and popularization Greek philosophy in the Muslim intellectual world.[36]

Most early writers on logic in Islamic philosophy during the 8th and 9th centuries produced commentaries on Aristotelian logic. The first original Arabic writings on logic were produced by al-Kindi, who produced a summary on earlier logic up to his time.[37]

 Philosophy of science

Al-Kindi made important contributions to the philosophy of science and the development of scientific methodology. Like his Arab predecessor Geber, al-Kindi placed a strong emphasis on experimentation, and in addition, he introduced a new emphasis on quantification. He also wrote the following on his view of scientific knowledge:[23]

We must not hesitate to recognize the truth and to accept it no matter what is its origin, no matter if it comes to us from the ancients or from foreign people... My purpose is first to write down all that the ancients have left us on a given topic and then, using the Arabic tongue and taking into account the customs of our time and our capacities, to complete what they have not fully expressed.

Though al-Kindi held ancient authorities (such as Aristotle) in high regard, he often criticized them for making claims regarding natural philosophy without providing any empirical proof, nor any empirical evidence or scientific demonstration. In many instances, al-Kindi used experiments and quantitative methods to verify many of his own theories, as he recognized the importance of direct observation and empiricism as a source of scientific knowledge. He also often invented specific laboratory apparatus in order to carry out his experiments.[2]


Two major theories of optics appear in the writings of al-Kindi; Aristotelian and Euclidian. Aristotle had believed that in order for the eye to perceive an object, both the eye and the object must be in contact_us with a transparent medium (such as air) that is filled with light. When these criteria are met, the "sensible form" of the object is transmitted through the medium to the eye. On the other hand, Euclid proposed that vision occurred in straight lines when "rays" from the eye reached an illuminated object and were reflected back. As with his theories on Astrology, the dichotomy of contact_us and distance is present in al-Kindi's writings on this subject as well.

The factor which al-Kindi relied upon to determine which of these theories was most correct was how adequately each one explained the experience of seeing. For example, Aristotle's theory was unable to account for why the angle at which an individual sees an object affects his perception of it. For example, why a circle viewed from the side will appear as a line. According to Aristotle, the complete sensible form of a circle should be transmitted to the eye and it should appear as a circle. On the other hand, Euclidian optics provided a geometric model that was able to account for this, as well as the length of shadows and reflections in mirrors, because Euclid believed that the visual "rays" could only travel in straight lines (something which is commonly accepted in modern science). For this reason, al-Kindi considered the latter preponderant.[38]

In his Kitab al-Shu'a'at (Book of the Rays), al-Kindi wrote the following criticism on Anthemius of Tralles for reporting how "ships were set aflame by burning mirrors during a naval battle" without empirical evidence:[2]

Anthemius should not have accepted information without proof... He tells how to construct a mirror from which twenty four rays are reflected on a single point, without showing how to establish where the rays unite at a given distance from the middle of the mirror's surface. We, on the other hand, have described this with as much evidence as our ability permits, furnishing what was missing, for he has not mentioned a definite distance.


As an Islamic psychologist, al-Kindi was a pioneer in experimental psychology. He was the first to use the method of experiment in psychology, which led to his discovery that sensation is proportionate to the stimulus.[39] He was also the earliest to realize the therapeutic value of music and attempted to cure a quadriplegic boy using music therapy.[9]

He also dealt with psychology in several other treatises: On Sleep and Dreams (a treatise on dream interpretation), First Philosophy, and Eradication of Sorrow. In the latter, he described sorrow as "a spiritual (Nafsani) grief caused by loss of loved ones or personal belongings, or by failure in obtaining what one lusts after" and then added: "If causes of pain are discernible, the cures can be found." He recommended that "if we do not tolerate losing or dislike being deprived of what is dear to us, then we should seek after riches in the world of the intellect. In it we should treasure our precious and cherished gains where they can never be dispossessed...for that which is owned by our senses could easily be taken away from us." He also stated that "sorrow is not within us we bring it upon ourselves." He developed cognitive methods to combat depression and discussed the intellectual operations of human beings.[40]

Philosophical thought


While Muslim intellectuals were already acquainted with Greek philosophy (especially logic), al-Kindi is credited with being the first real Muslim philosopher.[41] His own thought was largely influenced by the Neo-Platonic philosophy of Proclus, Plotinus and John Philoponus, amongst others, although he does appear to have borrowed ideas from other Hellenistic schools as well.[42] He makes many references to Aristotle in his writings, but these are often unwittingly re-interpreted in a Neo-Platonic framework. This trend is most obvious in areas such as metaphysics and the nature of God as a causal entity.[43] Earlier experts had suggested that he was influenced by the Mutazilite school of theology, because of the mutual concern both he and they demonstrated for maintaining the pure unity (tawhid) of God. However, such agreements are now considered incidental, as further study has shown that they disagreed on a number of equally important topics.[44]


According to al-Kindi, the goal of metaphysics is the knowledge of God. For this reason, he does make a clear distinction between philosophy and theology, because he believes they are both concerned with the same subject. Later philosophers, particularly al-Farabi and Avicenna, would strongly disagree with him on this issue, by saying that metaphysics is actually concerned with qua being, and as such, the nature of God is purely incidental.[45]

Central to al-Kindi's understanding of metaphysics is God's absolute oneness, which he considers an attribute uniquely associated with God (and therefore not shared with anything else). By this he means that while we may think of any existent thing as being "one", it is in fact both "one" and many". For example, he says that while a body is one, it is also composed of many different parts. A person might say "I see an elephant", by which he means "I see one elephant", but the term 'elephant' refers to a species of animal that contains many. Therefore, only God is absolutely one, both in being and in concept, lacking any multiplicity whatsoever. This understanding entails a very rigorous negative theology because it implies that any description which can be predicated to anything else, cannot be said about God.[46][44]

In addition to absolute oneness, al-Kindi also described God as the Creator. This means that He acts as both a final and efficient cause. Unlike later Muslim Neo-Platonic philosophers (who asserted that the universe existed as a result of God's existence "overflowing", which is a passive act), al-Kindi conceived of God as an active agent. In fact, of God as the agent, because all other intermediary agencies are contingent upon Him.[47] The key idea here is that God "acts" through created intermediaries, which in turn "act" on one another - through a chain of cause and effect - to produce the desired result. In reality, these intermediary agents do not "act" at all, they are merely a conduit for God's own action.[43] This is especially significant in the development of Islamic philosophy, as it portrayed the "first cause" and "unmoved mover" of Aristotelian philosophy as compatible with the concept of God according to Islamic revelation.[48]

However, in contrast to ancient Greek philosophers such as Aristotle who believed that the universe had an infinite past with no beginning, Al-Kindi believed that the universe has a finite past with a beginning. This view was inspired by the creation doctrine shared by the three Abrahamic religions: Judaism, Christianity and Islam. The Christian philosopher, John Philoponus, presented the first such argument against the ancient Greek notion of an infinite past. However, the most sophisticated medieval arguments against an infinite past were developed by Al-Kindi, Saadia Gaon (Saadia ben Joseph) and Al-Ghazali (Algazel). They developed two logical arguments against an infinite past, the first being the "argument from the impossibility of the existence of an actual infinite", which states:[49]

"An actual infinite cannot exist."

"An infinite temporal regress of events is an actual infinite."

" An infinite temporal regress of events cannot exist."

The second argument, the "argument from the impossibility of completing an actual infinite by successive addition", states:[49]

"An actual infinite cannot be completed by successive addition."

"The temporal series of past events has been completed by successive addition."

" The temporal series of past events cannot be an actual infinite."

Both arguments were adopted by later Christian philosophers and theologians, and the second argument in particular became more famous after it was adopted by Immanuel Kant in his thesis of the first antimony concerning time.[49]




Ancient Greek philosophers such as Plato and Aristotle would
 become  highly revered in the medieval Islamic world.

Al-Kindi theorized that there was a separate, incorporeal and universal intellect (known as the "First Intellect"). It was the first of God's creation and the intermediary through which all other things came into creation. Aside from its obvious metaphysical importance, it was also crucial to al-Kindi's epistemology, which was influenced by Platonic realism.[50]

According to Plato, everything that exists in the material world corresponds to certain universal forms in the heavenly realm. These forms are really abstract concepts such as a species, quality or relation, which apply to all physical objects and beings. For example, a red apple has the quality of "redness" derived from the appropriate universal. However, al-Kindi says that human intellects are only potentially able to comprehend these. This potential is actualized by the First Intellect, which is perpetually thinking about all of the universals. He argues that the external agency of this intellect is necessary by saying that human beings cannot arrive at a universal concept merely through perception. In other words, an intellect cannot understand the species of a thing simply by examining one or more of its instances. According to him, this will only yield an inferior "sensible form", and not the universal form which we desire. The universal form can only be attained through contemplation and actualization by the First Intellect.[51]

The analogy he provides to explain his theory is that of wood and fire. Wood, he argues, is potentially hot (just as a human is potentially thinking about a universal), and therefore requires something else which is already hot (such as fire) to actualize this. This means that for the human intellect to think about something, the First Intellect must already be thinking about it. Therefore he says that the First Intellect must always be thinking about everything. Once the human intellect comprehends a universal by this process, it becomes part of the individual's "acquired intellect" and can be thought about whenever he or she wishes.[52]

The soul and the afterlife

Al-Kindi believed that the soul is a simple, immaterial substance, which is related to the material world only because of its faculties which operate through the physical body. To explain the nature of our worldly existence, he (borrowing from Epictetus) compares it to a ship which has, during the course of its ocean voyage, temporarily anchored itself at an island and allowed its passengers to disembark. The implicit warning is that those passengers who linger too long on the island may be left behind when the ship sets sail again. Here, al-Kindi displays a stoic concept, that we must not become attached to material things (represented by the island), as they will invariably be taken away from us (when the ship sets sail again). He then connects this with a Neo-Platonist idea, by saying that our soul can be directed towards the pursuit of desire or the pursuit of intellect; the former will tie it to the body, so that when the body dies, it will also die, but the latter will free it from the body and allow it to survive "in the light of the Creator" in a realm of pure intelligence.[53]

Al-Kindi further wrote:

Our residence in this phenomenal world is transitory; it is a journey towards the eternal one. The most miserable man, is he who prefers for himself the material above the spiritual, for the material, apart from its ephemeral nature, obstructs our passage to the spiritual world. Man should not `disregard any means to protect himself against all human vices, and he should seek to rise to the highest ends of human virtues..., that is, to the knowledge by means of which we protect ourselves against spiritual and bodily disease, and acquire the human virtues in whose very essence goodness is grounded.[2]

The relationship between revelation and philosophy

In the view of al-Kindi, prophecy and philosophy were two different routes to arrive at the truth. He contrasts the two positions in four ways. Firstly, while a person must undergo a long period of training and study to become a philosopher, prophecy is bestowed upon someone by God. Secondly, the philosopher must arrive at the truth by his own devices (and with great difficulty), whereas the prophet has the truth revealed to him by God. Thirdly, the understanding of the prophet - being divinely revealed - is clearer and more comprehensive than that of the philosopher. Fourthly, the way in which the prophet is able to express this understanding to the ordinary people is superior. Therefore al-Kindi says the prophet is superior in two fields: the ease and certainty with which he receives the truth, and the way in which he presents it. However, the crucial implication is that the content of the prophet's and the philosopher's knowledge is the same. This, says Adamson, demonstrates how limited the superiority al-Kindi afforded to prophecy was.[54][55]

In addition to this, al-Kindi adopted a naturalistic view of prophetic visions. He argued that, through the faculty of "imagination" as conceived of in Aristotelian philosophy, certain "pure" and well-prepared souls, were able to receive information about future events. Significantly, he does not attribute such visions or dreams to revelation from God, but instead explains that imagination enables human beings to receive the "form" of something without needing to perceive the physical entity to which it refers. Therefore, it would seem to imply that anyone who has purified themselves would be able to receive such visions. It is precisely this idea, amongst other naturalistic explanations of prophetic miracles that al-Ghazali attacks in his Incoherence of the Philosophers.[56]


While al-Kindi appreciated the usefulness of philosophy in answering questions of a religious nature, there were many Islamic thinkers who were not as enthusiastic about the use of philosophy. However, it would be incorrect to assume that they opposed philosophy simply because it was a "foreign science". Oliver Leaman, an expert on Islamic philosophy, points out that the objections of notable theologians are rarely directed at philosophy itself, but rather at the conclusions the philosophers arrived at. Even al-Ghazali (famous for his critique of the philosophers, The Incoherence of the Philosophers), was himself an expert in philosophy and logic. Al-Ghazali's criticized the philosophers not for their methods, but for arriving at theologically erroneous conclusions. The three most serious of these, in his view, were believing in the co-eternity of the universe with God, denying the bodily resurrection, and asserting that God only has knowledge of abstract universals, not of particular things.[57]

During his life, al-Kindi was fortunate enough to enjoy the patronage of the pro-Mutazilite Caliphs al-Ma'mun and al-Mu'tasim, which meant he could carry out his philosophical speculations with relative ease. This would change significantly towards the end of his life when al-Mutawakkil supported the traditionalists, and initiated persecution of various unorthodox schools of thought, including the philosophers. In his own time, al-Kindi would be criticized for extolling the "intellect" as being the most immanent creation in proximity to God, a standing commonly held to be the position only of the angels.[58] He also engaged in disputations with the Mutazilites, whom he attacked for their belief in atoms.[59] But the real role of al-Kindi in the conflict between philosophers and theologians would be to prepare the ground for debate. His works, says Deborah Black, contained all the seeds of future controversy that would be fully realized in al-Ghazali's book, Incoherence of the Philosophers.[60]

Works translated into English

             The Medical Formulary of Aqrabadhın of Al-Kindi by M Levey (1966)

             Al-Kindi's Metaphysics: A Translation of Yaqub ibn Ishaq al-Kindi's Treatise "On First Philosophy" (Fi al-Falsafah al-Ula) by Alfred L. Ivry (1974)

             Scientific Weather Forecasting in the Middle Ages The Writings of Al-Kindi by Gerrit Bos and Charles Burnett (2000)

             al-Kindis Treatise on Cryptanalysis by M. Mrayati, Y. Meer Alam and M. H. at Tayyan (2003)


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             Robert L. Arrington (2001) [ed.] A Companion to the Philosophers. Oxford: Blackwell. ISBN 0-631-22967-1

             Peter J. King (2004) One Hundred Philosophers. New York: Barron's. ISBN 0-7641-2791-8

             Peter Adamson (2005) 'Al-Kindi'. In Peter Adamson & Richard C. Taylor (eds). The Cambridge Companion to Arabic Philosophy. Cambridge: Cambridge University Press.

             Peter Adamson (2006) Al-Kindi. Oxford: OUP.

             Felix Klein-Frank (2001) Al-Kindi. In Oliver Leaman & Hossein Nasr. History of Islamic Philosophy. London: Routledge.

             Henry Corbin (1993). History of Islamic Philosophy. London: Keagan Paul International.



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