Abu Yusuf Yaqub Is’haq Kindi

Abu Yusuf Yaqub Ibn Is’haq Kindi (c. 801–873 CE), was an Arab Iraqi polymath, an Islamic philosopher, scientist, astrologer, astronomer, cosmologist, chemist, logician, mathematician, musician, physician, physicist, psychologist, and meteorologist. 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, and as a pioneer in chemistry, medicine, music theory, physics, psychology,the philosophy of science, and is also known for being one of the fathers of ####cryptography. In mathematics, al-Kindi played an important role in introducing Indian numerals to the Islamic and Christian world. He was a pioneer in cryptanalysis and cryptology, and devised new methods of breaking ciphers, including the frequency analysis method. Using his mathematical and medical expertise, he developed a scale to allow doctors to quantify the potency of their medication. He also experimented with music therapy.

Astrology, astronomy, and cosmology
In astrology and astronomy, 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. In cosmology, 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. As an advanced chemist, 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. 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.

Medicine
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, and partly by his own personal experience and other Muslim physicians in his time.

Music theory
Kindi was the first great theoretician of music in the Arab-Islamic world. 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.

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. 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.

Philosophy of science
Al-Kindi made important contributions to the philosophy of science and the development of scientific methodology. Like his Arab predecessor Jābir ibn Hayyān, al-Kindi placed a strong emphasis on experimentation, and in addition, he introduced a new emphasis on quantification.

Physics
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 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 depends upon mathematically describable "rays" that reach out in straight lines from the eye to touch the object of vision. As with his theories on Astrology, the dichotomy of contact and distance is present in al-Kindi's writings on this subject as well.

Psychology
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. He was also the earliest to realize the therapeutic value of music and attempted to cure a quadriplegic boy using music therapy.

Metaphysics
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.

Epistemology
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.

Works translated into English
• The Medical Formulary of Aqra¯ba¯dhı¯n of Al-Kindi
• Al-Kindi's Metaphysics: A Translation of Yaqub ibn Ishaq al-Kindi's Treatise "On First Philosophy"
• Scientific Weather Forecasting in the Middle Ages The Writings of Al-Kindi
• al-Kindi’s Treatise on Cryptanalysis