Abu Yūsuf Yaʻqūb ibn
ʼIsḥāq aṣ-Ṣabbāḥ al-Kindī (/ælˈkɪndi/; Arabic: أبو يوسف يعقوب بن إسحاق الصبّاح الكندي; Latin: Alkindus; c. 801–873 AD) was an Arab Muslim philosopher, polymath,
mathematician, physician and musician. Al-Kindi was the first of the
Islamic peripatetic philosophers, and is hailed as the "father of Arab
philosophy".
Al-Kindi was born in
Kufa and educated in Baghdad. He 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 with "the philosophy of the ancients" (as Hellenistic
philosophy was often referred to by Muslim scholars) had a profound effect on
him, as he synthesized, adapted and promoted Hellenistic and Peripatetic
philosophy in the Muslim world. He subsequently wrote hundreds of original
treatises of his own on a range of subjects ranging from metaphysics, ethics,
logic and psychology, to medicine, pharmacology, mathematics, astronomy,
astrology and optics, and further afield to more practical topics like
perfumes, swords, jewels, glass, dyes, zoology, tides, mirrors, meteorology and
earthquakes.
In the field of mathematics, al-Kindi played an important role in
introducing Indian numerals to the Islamic world, and subsequently the Arabic
numerals to the Christian world, along with Al-Khwarizmi. Al-Kindi was also one
of the fathers of cryptography. Building on the work of Al-Khalil (717–786),
Al-Kindi's book entitled Manuscript on Deciphering Cryptographic Messages gave
rise to the birth of cryptanalysis, was the earliest known use of statistical
inference, and introduced several new methods of breaking ciphers, notably
frequency analysis. Using his mathematical and medical expertise, he was able
to develop a scale that would allow doctors to quantify the potency of their
medication.
The central theme underpinning al-Kindi's philosophical writings is the
compatibility between philosophy and other "orthodox" Islamic
sciences, particularly theology. And many of his works deal with subjects that
theology had an immediate interest in. These include the nature of God, the
soul and prophetic knowledge. But 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.
Early
life
Al-Kindi was born in
Kufa to an aristocratic family of the Kinda tribe, descended from the chieftain
al-Ash'ath ibn Qays, a contemporary of Muhammad. The family belonged to the
most prominent families of the tribal nobility of Kufa in the early Islamic
period, until it lost much of its power following the revolt of Abd al-Rahman
ibn Muhammad ibn al-Ash'ath. His father Ishaq was the governor of Kufa, and
al-Kindi received his preliminary education there. He later went to complete
his studies in Baghdad, where he was patronized by the Abbasid caliphs
al-Ma'mun (ruled 813–833) and al-Mu'tasim (r. 833–842). On account of his
learning and aptitude for study, al-Ma'mun appointed him to the House of
Wisdom, a recently established centre for the translation of Greek
philosophical and scientific texts, in Baghdad. He was also well known for his
beautiful calligraphy, and at one point was employed as a calligrapher by
al-Mutawakkil.
When al-Ma'mun died, his brother, al-Mu'tasim became Caliph. Al-Kindi's
position would be enhanced under al-Mu'tasim, who appointed him as a tutor to
his son. But on the accession of al-Wāthiq (r. 842–847), and especially of
al-Mutawakkil (r. 847–861), al-Kindi's star waned. There are various theories
concerning this: some attribute al-Kindi's downfall to scholarly rivalries at
the House of Wisdom; others refer to al-Mutawakkil's often violent persecution
of unorthodox Muslims (as well as of non-Muslims); at one point al-Kindi was
beaten and his library temporarily confiscated. Henry Corbin, an authority on
Islamic studies, says that in 873, al-Kindi died "a lonely man", in
Baghdad during the reign of al-Mu'tamid (r. 870–892).
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. Felix
Klein-Franke suggests a number of reasons for this: aside from the militant
orthodoxy of al-Mutawakkil, the Mongols also destroyed countless libraries
during their invasion. However, he says the most probable cause of this was
that his writings never found popularity amongst subsequent influential
philosophers such as al-Farabi and Avicenna, who ultimately overshadowed him.
Accomplishments
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). 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.
Philosophy
His greatest contribution to the development of Islamic philosophy was his
efforts to make Greek thought both accessible and acceptable to a Muslim
audience. Al-Kindi carried out this mission from the House of Wisdom (Bayt
al-Hikma), an institute of translation and learning patronized by the Abbasid
Caliphs, in Baghdad. 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.
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. And while his philosophical
approach was not always original, and was even considered clumsy by later
thinkers (mainly because he was the first philosopher writing in the Arabic
language), he successfully incorporated Aristotelian and (especially)
neo-Platonist thought into an Islamic philosophical framework. This was an
important factor in the introduction and popularization of Greek philosophy in
the Muslim intellectual world.
Astronomy
Al-Kindi took his view
of the solar system from Ptolemy, who placed 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); the
appearance and manner of people varies according to the arrangement of heavenly
bodies situated above their homeland.
However, he is
ambiguous when it comes to the actual 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 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 and action at a
distance. This dichotomy is duplicated in his writings on optics.
Some of the notable
astrological works by al-Kindi include:
· The Book of the
Judgement of the Stars, including The Forty Chapters, on
questions and elections.
· On the Stellar Rays.
· Several epistles on
weather and meteorology, including De mutatione temporum, ("On
the Changing of the Weather").
· Treatise on the
Judgement of Eclipses.
· Treatise on the
Dominion of the Arabs and its Duration (used to predict the end of Arab rule).
· The Choices of Days (on elections).
· On the Revolutions of
the Years (on mundane astrology and natal revolutions).
· De Signis Astronomiae
Applicitis as Mediciam ‘On the Signs of Astronomy as applied to
Medicine’
· Treatise on the
Spirituality of the Planets.
Optics
De radiis, manuscript, 17th
century. Cambridge, Trinity College Library, Medieval manuscripts, MS
R.15.17 (937).
Al-Kindi was the first major writer on optics since antiquity. Roger Bacon
placed him in the first rank after Ptolemy as a writer on the topic. In a work
known in the west as De radiis stellarum, al-Kindi developed a theory
"that everything in the world ... emits rays in every direction, which
fill the whole world." This theory of the active power of rays had an
influence on later scholars such as Ibn al-Haytham, Robert Grosseteste and
Roger Bacon.
Two major theories of optics appear in the writings of al-Kindi;
Aristotelian and Euclidean. Aristotle had believed that in order for the eye to
perceive an object, both the eye and the object must be in contact 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 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,
Euclidean 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.
Al-Kindi's primary optical treatise "De aspectibus" was later
translated into Latin. This work, along with Alhazen's Optics and the Arabic
translations of Ptolemy and Euclid's Optics, were the main Arabic texts to
affect the development of optical investigations in Europe, most notably those
of Robert Grosseteste, Vitello and Roger Bacon.
Medicine
There are more than
thirty treatises attributed to al-Kindi in the field of medicine, in which he
was chiefly influenced by the ideas of Galen. His most important work
in this field is probably De Gradibus, in which he demonstrates the
application of mathematics to medicine, particularly in the field of pharmacology.
For example, he developed a mathematical scale to quantify the strength of 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. According to Plinio Prioreschi, this was the first attempt at
serious quantification in medicine.
Chemistry
As an
advanced chemist, Al-Kindi was also an opponent of alchemy; he
debunked the myth that simple, base metals could be transformed into precious
metals such as gold or silver.
Al-Kindi unambiguously
described the distillation of wine. In a book titled as Kitab al-Taraffuq
fi al-‘itr (The Book of the chemistry of Perfume and distillations), he says,
after describing the method and apparatus needed for distillation: “In
this way one can distill wine using a water-bath, and it comes out the same
color as rose-water”. Also in the same book, he describes
the distillation process for extracting rose oils, and provides
the recipes for 107 different kinds of perfumes.
Mathematics
Al-Kindi authored works
on a number of 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. 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.
Cryptography
The first page of
al-Kindi's manuscript "On Deciphering Cryptographic Messages",
containing the oldest known description
of cryptanalysis by frequency analysis.
Al-Kindi is credited
with developing a 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). His book on this topic is Risāla fī
Istikhrāj al-Kutub al-Mu'ammāh (رسالة في
استخراج الكتب المعماة; literally: On Extracting Obscured
Correspondence, more contemporary: On Decrypting Encrypted
Correspondence). In his treatise on cryptanalysis, he wrote:
One way to solve an
encrypted message, if we know its language, is to find a different plaintext of
the same language long enough to fill one sheet or so, and then we count the
occurrences of each letter. We call the most frequently occurring letter the
"first", the next most occurring letter the "second", the
following most occurring letter the "third", and so on, until we
account for all the different letters in the plaintext sample. Then we look at
the cipher text we want to solve and we also classify its symbols. We find the
most occurring symbol and change it to the form of the "first" letter
of the plaintext sample, the next most common symbol is changed to the form of
the "second" letter, and the following most common symbol is changed
to the form of the "third" letter, and so on, until we account for
all symbols of the cryptogram we want to solve.
Al-Kindi was influenced
by the work of Al-Khalil (717–786), who wrote the Book of
Cryptographic Messages, which contains the first use of permutations
and combinations to list all possible Arabic words with and
without vowels.
Meteorology
In a treatise entitled
as Risala fi l-Illa al-Failali l-Madd wa l-Fazr (Treatise
on the Efficient Cause of the Flow and Ebb), Al-Kindi presents a theory
on tides which "depends on the changes which take place in
bodies owing to the rise and fall of temperature." In order to
support his argument, he gave a description of a scientific experiment as
follows:
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.
In explaining the
natural cause of the wind, and the difference for its directions based on
time and location, he wrote:
When the sun is in its
northern declination northerly places will heat up and it will be cold towards
the south. Then the northern air will expand in a southerly direction because
of the heat due to the contraction of the southern air. Therefore most of the
summer winds are merits and most of the winter winds are not.
Music
theory
Al-Kindi was the first
great theoretician of music in the Arab-Islamic world. He is known to have
written fifteen treatises on music theory, but only five have survived. He
added a fifth string to the 'ud. His works included discussions on
the therapeutic value of music and what he regarded as
"cosmological connections" of music.
Philosophical
thought
Influences
While Muslim intellectuals were already acquainted with Greek philosophy
(especially logic), al-Kindi is credited with being the first real Muslim
philosopher. 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.
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.
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 singularity (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.
Metaphysics
According to al-Kindi, the goal of metaphysics is the knowledge of God. For
this reason, he does not 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 being qua being, and as such, the nature of God is purely
incidental.
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. Some feel 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.
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. 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. 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.
Epistemology
Ancient Greek philosophers such as Plato and Aristotle were highly
respected 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.
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.
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.
The
soul and the afterlife
Al-Kindi says 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.
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.
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.
Critics
and patrons
While al-Kindi appreciated the usefulness of philosophy in answering
questions of a religious nature, there would be many Islamic thinkers who were
not as enthusiastic about its potential. But 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, who
is famous for his critique of the philosophers, was himself an expert in
philosophy and logic. And his criticism was that they arrived 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 (not all philosophers subscribed to these same views).
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. In his own time,
al-Kindi would be criticized for extolling the "intellect" as being
the most immanent creation in proximity to God, which was commonly held to be
the position of the angels. He also engaged in disputations with the
Mutazilites, whom he attacked for their belief in atoms. 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
Incoherence of the Philosophers.
Legacy
Al-Kindi was a master
of many different areas of thought and was held to be one of the
greatest Islamic philosophers of his time. His influence in the
fields of physics, mathematics, medicine, philosophy and music were
far-reaching and lasted for several centuries. Ibn al-Nadim in
his al-Fihrist praised Al-Kindi and his work stating:
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.
Al-Kindi major
contribution was his establishment of philosophy in the Islamic world and his
efforts in trying to harmonize the philosophical investigation along with the
Islamic theology and creed. The philosophical texts which were translated under
his supervision would become the standard texts in the Islamic
world for centuries to come, even after his influence has been eclipsed by
later Philosophers.
Al-Kindi was also an important figure in medieval Europe. Several of
his books got translated into Latin influencing western authors
like Robert Grosseteste and Roger Bacon. The Italian Renaissance
scholar Geralomo Cardano (1501–1575) considered him as one of the
twelve greatest minds.
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