The ninth-century A.C. forms the golden period of the development of Islamic learning when the Arabs were the real standard-bearers of civilization. They not only saved Greek learning from total extinction but also made lasting contributions to almost all branches of knowledge and made considerable advancement in diverse spheres of human activity. The distinguished scientists during the first half of the IXth century were Al Kindi, Al Khwarizmi, and Al Farghani.
Al Kindi, an encyclopaedist and a versatile genius was regarded by Cardan, a philosopher of Renaissance as ‘one of the 12 subtlest minds.’ According to Abu Maashar, the author of Mozakkarat, Al Kindi was considered among the four greatest translators that the Muslim world had produced.
Abu Yusuf Yaqub ibn Ishaq al Kindi, who belonged to the South Arabian tribe of Kinda was born in Basrah in the beginning of the 9th century A.C. He is known as Al Kindus in the West. His father, Ishaq ibn Saleh, was posted as the Governor of Kufa during the reigns of three Abbaside Caliphs Mehdi, Hadi and Haroon ar-Rashid. Young Kindi, who was of pure Arab descent, was entitled as the ‘Philosopher of Arabs.’ He received his education in Basrah and Baghdad where he served in various capacities under three Abbaside Caliphs Mamoon, Mutasim, and Mutawakkil. He was a favorite of Caliph Mamoon ar-Rashid and was given every kind of state patronage. He was, however, persecuted under the orthodox reaction led by Al Mutawakkil (847-861 A.C.). He had acquired great knowledge in medicine, philosophy, mathematics, occult sciences, astronomy, music and logic. He had mastered Persian, Greek and Indian learning and was well versed in Hebrew, Greek and Arabic languages. First of all, he was appointed as translator and editor of Greek works during the reign of Mamoon. He also served as a tutor of a son of Mutasim and was later on attached as an astrologer to the Abbaside Court. He was persecuted by Mutawakkil and his library was confiscated. He died in 873 A.C.
Al Kindi, an encyclopedic scientist, made invaluable contributions to mathematics, astrology, astronomy, physics, optics, music, medicine, pharmacy, philosophy and logic. Authorship of no less than 265 works is ascribed to him, of which only a few have survived in original language. But, a good deal are still extant in Latin translations made by Gerard of Cremona. According to historical records, out of his 265 works, 22 dealt with philosophy, 19 with astronomy, 16 with astrology, 7 with music, 11 with mathematics, 22 with numerals, 22 with medicine, 21 with politics, 33 with physics, 9 with logic and the rest with other branches of knowledge. He wrote four books on the use of Hindu numerals. He made and revised a number of translations of Greek works into Arabic. He wrote a number of invaluable treatises dealing with precious stones. He considered alchemy as an imposture and has dealt with this subject in one of his treatises.
He is the most dominating figure in Mediaeval science and one of the greatest Muslim scholars in physics. Over and above he was an astrologer, philosopher, mathematician, alchemist, optician and musical theorist: Of his hundreds of works, fifteen are on meteorology, several on specific weight, on tides, on optics and on reflection of light. Two of his most important scientific works are :
- De Aspectibus, a treatise on geometrical and physiological optics which influenced Roger Bacon, Wirelo and other Western scientists.
- De Medicinarum Compositarum Gradibus is an exceptional treatise in which an attempt has been made to establish posology on a mathematical basis. “His principal work on geometrical and physiological optics,” writes Phillip K. Hitti, “based on the optics of Euclid in Theon’s, recension, was widely used both in East and West until superseded by the greater work of Ibn al-Haitham. In this invaluable optical work, Al Kindi has dealt with the passage of light in straight lines; direct process of vision; the process of vision by looking glass and the influence of distances and angle of vision or sight along with optical delusions. He says that light takes no time to travel and vision takes place through a bundle of rays, which, sent out from the eye expanding in the form of a cone, embrace the object. While the other four senses receive impression from things, the sense of sight grasps its object in an active and instantaneous manner.”
One of his treatises translated into Latin deals with the causes of the blue colour of the sky: According to him, this ‘colour is not really special to heavens but arises from the mixture of the darkness of the sky with the light of the atoms of dust, vapour, etc. In the air illuminated by the light of the Sun.’ He had composed a remarkable work on ebb and flow which has been translated into Latin. He incorporated his theories in this book after personally testing them through experiments. He wrote several small treatises on iron and steel to be used for weapons. He applied mathematics not only to physics but also to medicine. He thought that gold and silver could only be obtained from mines and not through any other process. He endeavoured to ascertain the laws that govern the fall of bodies, hence he may be considered as the forerunner of the Theory of Gravity, propounded by Newton.
He was a reputed astrologer and during his lifetime he could forestall the duration of about 450 years for Abbaside Caliphate which was then threatened by Carmathians. He was considered among the nine Judicas of astrology.
The reign of the Abbaside Caliph Mamoon constitutes the most glorious epoch in Islamic history, and has rightly been called the Augustan age of Islam. Al-Kindi founded the House of Wisdom, in which philosophy acquired its real progress. He translated and wrote commentaries on a number of philosophical works of Aristotle. His theory of the Universe is similar to the theory of Aristotle, Being a natural philosopher he has extensively discussed the doctrine of soul and intelligence. The divine intelligence is the cause of the existence of the world. According to him, “the world as a whole is the work of an externally active cause, the Divine intelligence, whose activity is transmitted in many ways from above to the world. Between God and the world or bodies is the world of soul, which created the world of heavenly spheres. In so far as the human soul is combined with the body, it is dependent on the influence of heavenly bodies, but in its spiritual origin and being it is free.” Both immortality and freedom could only be acquired in the world of intelligence. If anyone attains these two, his intellectual power is developed to such an extent that he may acquire true knowledge about God and the Universe. Thus in De Intellectu the Latin translation of the philosophical work of Al Kindi which was edited by Nagy, the Western world found for the first time the doctrine of Intelligence.
Al Kindi is one of the greatest musical theorists who has written more than half a dozen treatises on music. “In one of which,” says George Sarton, “we find the first definite use of notation among the Arabs. He is the earliest writer on music whose work has come down to us.” His works contain notation for the determination of the pitch. Out of his seven treatises on music, three have been preserved up to the present time, namely, “The Essentials of Knowledge in Music; On the Melodies and “The Necessary Book on the Composition of Melodies.” In one of his treatises, Al Kindi describes rhythm (iqa) as constituent part of Arabian music. “Measured song or mensural music,” writes Phillip K. Hitti, “must, therefore, have been known to the Muslims centuries before it was introduced in Europe.” Ahmad ibn Muhammad Al Sarakhsi (d 899 A.C.) and Mansoor ibn Talha ibn Tahir who were disciples of Al Kindi wrote a number of books on musical theories. The former has to his credit at least half a dozen books on the subject.
The writings of. Al Kindi deeply influenced the Eastern and Western thinkers in diverse spheres of knowledge. A number of his works were first translated into Latin by Gerard of Cremona, whose study obliged Cardan to consider him as one of the 12 greatest minds born in the world since the creation of the universe till the middle of the 16th century A.C. His writings on optics greatly influenced Roger Bacon and other Western scientists who considered him along with Alhazen and Ptolemy as one of the three greatest authorities on the subject.