Al-Kindi was an Arab Muslim philosopher, polymath, mathematician, physician and musician.
Background
Al-Kindi was born in Kufa in 801 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.
Education
Al-Kindi received his preliminary education in Kufa. 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). He was taught the Qu’ran, mathematics, Arab grammar and literature, fiqh and kalam (speculative theology), and the Greek and Syraic languages. He was known for his beautiful calligraphy.
Career
Throughout most of his career al-Kindi held a position as court scholar in Baghdad. He acted as tutor to the son of al-Mutasim (reigned 833-842), dedicating several works to his young pupil. Under the conservative caliph al-Mutawakkil (reigned 847-861), however, al-Kindi was disgraced and his position at court terminated. Little is known of his later life. He seems to have continued his work as a private scholar until his death.
As the first outstanding Arabian scholar, al-Kindi received the honorific title Faylasuf al-Arab (the philosopher of the Arabs). His works are extensive in both number and subject. He composed in Arabic well over 300 treatises and translations. Primarily an encyclopedist, he wrote not only on philosophy and logic but also on arithmetic, geometry, astronomy, meteorology, optics, medicine, politics, and music. Medieval Europe was familiar with only a portion of his writings, the most important being On the Intellect and What Is Understood, On Sleep and Vision, On the Five Essences, Introduction to the Art of Logical Demonstration, The Theory of the Magical Arts, and The Agent in the Proper Sense and in the Metaphorical Sense.
On the Intellect, the most influential of these works, was written to clarify Aristotle's distinction between that portion of the intellect that receives knowledge (the possible intellect) and that portion of the intellect that causes knowledge by reproducing intelligible objects (the active, or agent, intellect). The agent intellect al-Kindi considered to be a spiritual being or substance distinct from the human soul and outside the individual person.
Following the precedent of Alexander of Aphrodisias, al-Kindi thus identified the agent intellect of Aristotle with the last of the Neoplatonic Intelligences that emanate from God to effect and sustain creation. This concept of one separate agent intellect for all men remained a major tenet of the Arabian philosophers. It explained human knowledge as a product of outside stimulation and, inasmuch as the human personality and soul were strongly dependent upon the active reason, it implied a denial of personal survival after death.
Al-Kindi died "a lonely man", in Baghdad during the reign of al-Mu'tamid in 873.
Religion
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.
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.
Views
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.
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.
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.
Quotations:
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. "