De Gradibus

De Gradibus (Latin: Concerning degrees) was written by the Father of Arab Philosophy, Al-Kindi (801-873CE). In it, he applies mathematics to medicine, demonstrating a method he invented to determine the proper strength of a drug for a patient. Also, he discusses the degrees of the phases of the moon and how they help a physician to determine the most crucial days of a patient's illness.

When it was translated into Latin, the complex mathematical reasoning made it difficult for Western Europeans to grasp. Roger Bacon appreciated his approach, and endorsed it thusly:

The degree can only be determined by the method taught by Al-Kindi’s De gradibus, one extremely difficult and almost entirely unknown among Latin physicians of these days, as everyone is aware. Whoever wants to become perfect in this philosopher’s art must know the fundamentals of mathematics, because the species of greater and lesser inequality, the species of ratios, and the very difficult rules of fractions are all used by this author.

Plinio Prioreschi, a 20th century expert on the history of medicine, credits Al-Kindi with the earliest attempt to quantify medicine.

Al-Kindi was heavily influenced by noted Greek physician Galen (129-216CE). The stereotype of a Muslim rejecting any non-Muslim source of knowledge is tossed out by Al-Kindi's approach to knowledge. He wrote:

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.

How did Arabic works come to be available to European scholars. Was it haphazard, or was there a deliberate move to share knowledge. Tomorrow we will learn about Gerard of Cremona, and for a double treat, we will also talk about Gerard of Cremona. (Not a typo.)

Al-Kindi

Abu Yūsuf Yaʻqūb ibn ʼIsḥāq aṣ-Ṣabbāḥ al-Kindī (801-873CE) is called the Father of Arab philosophy. Born in Kufa and educated in Baghdad, he was instrumental in the translation of many Greek scholarly texts into Arabic. (Remember that a lot of classical scholarly knowledge came to Western Europe via Arabic translations.) He is also credited with introducing Indian numerals (what we mistakenly think of as Arabic numerals) into the Arab and western world.

He was a polymath who contributed to many fields, although he did not always find the scientific truth.

In astronomy he followed Ptolemy's geocentric theory of the solar system, and he was certain the planets followed circular orbits in obedience to God.

He was a chemist who debunked the idea of alchemy turning base metals into gold or silver. He was the first to distill pure ethanol, with which he created several perfumes. He also created cosmetics and pharmaceuticals, and wrote a book on the chemistry of perfume.

A recently discovered book of his in Istanbul, entitled (in English) A Manuscript on Deciphering Cryptographic Messages shows that he was a pioneer in cryptography with the first known explanation of how to decipher encrypted messages by analyzing the frequency of letters.

He wrote on pollution, environmentalism, and meteorology, and explained tides as a result of heating and cooling.

He published 15 treatise on music theory—five of which have survived—including the first known written use of the term "music" (musiqia); he urged the use of music in therapy.

In optics, he explained that both the eye and the object seen must be linked by a transparent medium (air) filled with light. He criticizes Anthemius of Trailes for reporting that sunlight could be focused in war to cause opposing warships to burst into flame. Anthemius did not witness it himself. Al-Kindi performed experiments to be certain this would actually work.

His theory that time, space, motion, and bodies were not absolutes but relative to other objects and the observer puts him closer to Einstein than to Galileo and Newton.

Although his belief that philosophy could support theology was contested by many Arabic scholars who followed him, his writings laid the groundwork much of Arabic philosophy to come.

He also applied mathematics to pharmacology, which I'll talk about tomorrow.