7. Al-Kindi
(175-260H/800-873AD)

Al-Kindi was known as the Philosopher of the Arabs and was considered "as one of the 12 geniuses endowed with a high level of intelligence"(32). He was an encyclopedic scholar. Besides his fame as philosopher, he was mathematician, astronomer, physicist, physician, pharmacist and geographer.

His full name was Yaqub Ibn Ishaq Ibn Sabah al-Kindi Abu Yuusuf. He hailed from al-Kinda tribe and was known in Latin by Alkindus. He was born at Kufa where his father was governor(33).

Al-Kindi grew up and studied in al-Basra. Later he moved to Baghdad where he furthered his studies with the most reputed scholars. He was a contemporary of three Abbasid caliphs, al-Mamun, al-Mu'tasim and al-Mutawakkil as well as the three astronomers, the Banu Musa brothers and the astronomer Sanad Ibn Ali. He was held in such a high esteem by al-Ma'mun and al-Mu'tasim that al-Ma'mun entrusted him with the task of translating Aristotle's books as well as other Greek philosophers. He vas also used by al-Mutawakkil as calligrapher. On account of his philosophical views and denunciation by envious people, al-Mutawakkil ordered the confiscation of all his books. These were, however, all returned to him later.

Scientific Contributions

He wrote four books on the use of Indian numerals and made considerable contribution to spherical geometry which he used in his astronomical studies(34).

He observed the positions of stars and planets -particularly the Sun and the Moon- in comparison to Earth and their eventual natural impact as well as the arising phenomena. He came up with breakthrough and bold views in his research, including on the origin of life on Earth. This forced several scholars to recognize him as a high level thinker(35).

In chemistry, he challenged the idea that precious metals, such as gold can be extracted from base metals. He wrote a treatise that he called "Treatise in Opposition of Alchemists Pretending to Make Gold and Silver and their Trickeries".

In astronomy, al-Kindi did not believe in the influence of the planets on people's fate and refuted the astrologer's predictions based upon the motion of celestial bodies. He focused instead his interest on the scientific study of the Universe and stars based on their observation. Some historians considered him as one of eight outstanding astronomers in the Middle Ages(36).

In physics, he made rich contributions to geometrical and physiological optics and wrote a book on the subject, which had a great influence later on Roger Bacon, Witelo and other scholars(37).

Al-Kindi was also a brilliant engineer whose publications and theories were used as reference in construction works, mainly canals as was the case during the digging of canals between the Tigris and Euphrates rivers(38).

In medicine, his chief contribution was his attempt to systematically determine the doses to be administered of all the drugs known at his time(39).

Major Works

Al-Kindi was a prolific writer; he wrote and explained several books. Views differ as to the total number of his works which range between 230, 270 and 300 monographs and books. In these books, he tackled various subjects, including philosophy, astronomy, arithmetic, geometry, medicine, physics, logic, tides, metals, precious stones, iron and sword types. He was also an early translator of Greek works into Arabic.

Only some of his works will be presented, based on the statements of Tawkan(40) and Zarkali(41) :

- Risalah fi Madkhal Ila Aritmetica (Introduction to Arithmetic) : 5 monographs;

- Risalah fi Isti'mal al-Hissab al-Hindi (Use of Indian Calculation) : 4 monographs;

- Risalah fi 'ilal al-Awda' Noujoumia (Positions of the Stars);

- Risalah fi Sina'at al-Usturlab (Making of the Astrolabe);

- Ilahyat-e-Aristu (Aristotelian Philosophy) ;

- Aduiyah al-Murakkab (Compound Drugs);

- Rissalat al-Mosiqa (Treatise in Music);

- Al-Mad wa al-Jazr  (Tides) and

- Assuyuf wa Ajnassuha (Swords).

Gerard of Cremona translated a large number of al-Kindi's books into Latin. Their influence on the development of several scientific fields continued throughout several centuries.