The next great philosopher was Muhammad b. Muhammad b. Tarkhan Abu Nasr al-Farabi (d. 339), of Turkish descent. He was “a celebrated philosopher, the greatest indeed that the Muslims ever had; he composed a number of works on logic, music, and other sciences. No Musulman ever reached in the philosophical sciences the same rank as he, and it was by the study of his writings and the imitation of his style that Avicenna attained proficiency and rendered his own works so useful.” (Ibn Khallikan, iii. 307). He was born at Farab or Otrar near Balasaghum, but travelled widely. In the course of his wanderings he came to Baghdad but, as at the time he knew no Arabic, he was unable to enter into the intellectual life of the city. He set himself first to acquire a knowledge of the Arabic language, and then became a pupil of the Christian physician Matta b. Yunus, who was at that time a very old man, and under him he studied logic. To increase his studies he removed to Harran, where he met the Christian philosopher Yuhanna b. Khailan, and continued to work at logic under his direction. He then returned to Baghdad, where he set to work at the Aristotelian philosophy, in the course of his studies reading the de anima 200 times, the Physics 40 times. His chief interest, however, was in logic, and it is on his logical work that his fame chiefly rests. From Baghdad he went to Damascus, and thence to Egypt, but returned to Damascus, where he settled for the rest of his life. At that time the empire of the Khalifa of Baghdad was beginning to split up into many states, just like the Roman Empire under the later Karlings, and the officials of the Khalifate were forming semi-independent principalities under the nominal suzerainty of the Khalif and establishing hereditary dynasties. The Hamdanids Shi`ites, who began to rule in Mosul in 293, established themselves at Aleppo in 333 and achieved great fame and power as successful leaders against the Byzantine emperors. In 334 (= 946 A.D.) the Hamdanid Prince Sayf ad-Dawla took Damascus, and al-Farabi lived under his protection. At that period the orthodox were distinctly reactionary, and it was the various Shi`ite rulers who showed themselves the patrons of science and philosophy.

At Damascus al-Farabi led a secluded life. Most of his time he spent by the borders of one of the many streams which are so characteristic a feature of Damascus, or in a shady garden, and here he met and talked with his friends and pupils. He was accustomed to write his compositions on loose leaves, “for which reason nearly all his productions assume the form of detached chapters and notes; some of them exist only in fragments and unfinished. He was the most indifferent of men for the things of this world; he never gave himself the least trouble to acquire a livelihood or possess a habitation. Sayf al-Dawla settled on him a daily pension of four dirhams out of the public treasury, this moderate sum being the amount to which al-Farabi had limited his demand.” (Ibn Khallikan, iii. 309-310.)

Al-Farabi was the author of a series of commentaries on the logical Organon, which contained nine books according to the Arabic reckoning, namely:

  1. The Isagoge of Porphyry.
  2. The Categories or al-Maqulat.
  3. The Hermeneutica or al-´Ibara or al-Tafsir.
  4. The Analytica Priora or al-Qiyas I.
  5. The Analytica Posteriora or al-Burhan.
  6. The Topica or al-Jadl.
  7. The Sophistica Elenchi or al-Maghalit.
  8. The Rhetoric or al-Khataba.
  9. The Poetics or ash-Shi`r.

He also wrote an “Introduction to Logic” and an “Abridgment of Logic”; indeed, as we have already noted, his main work lay in the exposition of logic. He took some interest in political science and edited a summary of the laws of Plato, which very often replaces the Politics in the Arabic Aristotelian canon. In Ethics he wrote a commentary on the Nicomachæan Ethics of Aristotle, but ethical theory did not, as a rule, appeal greatly to Arabic students. In natural science he was the author of commentaries on the Physics, Meteorology, de coelo et de mundo of Aristotle, as well as of an essay “On the movement of the heavenly spheres.” His work in psychology is represented by a commentary on Alexander of Aphrodisias’ commentary on the De Anima, and by treatises “On the soul,” “On the power of the soul,” “On the unity and the one,” and “On the intelligence and the intelligible,” some of which afterwards circulated in mediæval Latin translations, which continued to be reprinted well into the 17th century (e.g., De intelligentia et de intelligibili. Paris, 1638). In metaphysics he wrote essays on “Substance,” “Time,” “Space and Measure,” and “Vacuum.” In mathematics he wrote a commentary on the Almagesta of Ptolemy, and a treatise on various problems in Euclid. He was a staunch upholder of the neo-Platonic theory that the teaching of Aristotle and that of Plato are essentially in accord and differ only in superficial details and modes of expression; he wrote treatises “On the agreement between Plato and Aristotle” and on “The object before Plato and Aristotle.” In essays “Against Galen” and “Against John Philoponus” he criticised the views of those commentators, and endeavoured to defend the orthodoxy of Aristotle by making them responsible for apparent discrepancies with the teaching of revelation. He was interested also in the occult sciences, as appears from his treatises “On geomancy,” “On the Jinn,” and “On dreams.” His chemical treatise called kimiya t-Tabish, “the chemistry of things heated,” has been classed as a work on natural science and also as a treatise on magic; this was the unfortunate direction which Arabic chemistry was taking. He also wrote several works on music. (Cf. Schmölders: Documenta Philos. Arab. Bonn., 1836, for Latin versions of select treatises).

As we have already noted, his primary importance was as a teacher of logic. A great deal of what he has written is simply a reproduction of the outlines of the Aristotelian logic and an exposition of its principles, but De Vaux (Avicenne, pp. 94-97) has drawn attention to evidences of original thought in his “Letter in reply to certain questions.”

Like al-Kindi he accepted the Theology as a genuine work of Aristotle, and shows very clear traces of its influences. In his treatise “On the intelligence” he makes a careful analysis of the way in which the term `aql (reason, intelligence, spirit) is employed in general speech and in philosophical enquiry. In common language “a man of intelligence” denotes a man of reliable judgment, who uses his judgment in an upright way to discern between good and evil, and thus is distinguished from a crafty man who employs his mind in devising evil expedients. Theologians use the term `aql to denote the faculty which tests the validity of statements, either approving them as true or rejecting them as false. In the Analytica Aristotle uses “intelligence” for the faculty by which man attains directly to the certain knowledge of axioms and general abstract truths without the need of proof; this faculty al-Farabi explains as being the part of the soul in which intuition exists, and which is thereby able to lay hold of the premises of speculative science, i.e., the reason of intelligence proper as the term is employed in the de anima, the rational soul which Alexander of Aphrodisias takes as an emanation from God. Following al-Kindi, al-Farabi speaks of four faculties or parts of the soul: the potential or latent intelligence, intelligence in action, acquired intelligence, and the agent intelligence. The first is the `aql hayyulani, the passive intelligence, the capacity which man has for understanding the essence of material things by abstracting mentally that essence from the various accidents with which it is associated in perception, more or less equivalent to the “common sense” of Aristotle. The intelligence in action or `aql bi-l-fi`l is the potential faculty aroused to activity and making this abstraction. The agent intelligence or `aql fa``al is the external power, the emanation from God which is able to awaken the latent power in man and arouse it to activity, and the acquired intelligence or `aql mustafad is the intelligence aroused to activity and developed under the inspiration of the agent intelligence. Thus the intelligence in action is related to the potential intellect as form is to matter, but the agent intelligence enters from outside, and by its operation the intelligence receives new powers, so that its highest activity is “acquired.”

Al-Farabi appears throughout as a devout Muslim, and evidently does not appreciate the bearing of the Aristotelian psychology on the doctrine of the Qur´an. The earlier belief of Islam, as of most religions, was a heritage from primitive animism, which regarded life as due to the presence of a perfectly substantial, though invisible, thing called the soul: a thing is alive so long as the soul is present, it dies when the soul goes away. In the earlier forms of animism this is the explanation of all movement: the flying arrow has a “soul” in it so long as it moves, it ceases to move when this soul goes away or desires to rest. This involves no belief in the immortality of the soul, nor is the soul invested with any distinct personality, all that comes later; it is simply that life is regarded as a kind of substance, very light and impalpable but perfectly self-existent. What may be described as the “ghost” theory marks a later stage of evolution, when the departed soul is believed to retain a distinct personality and still to possess the form and some at least of the sensations associated with the being in which it formerly dwelt. Such was the stage reached by Arab psychology at the time of the preaching of Islam. The Aristotelian doctrine represented the soul as containing different energies or parts, such as it had in common with the vegetable world and such others as it possessed in common with the lower kinds of animals: that is to say the faculties of nutrition, reproduction, and all the perceptions obtained from the use of the organs of sense, as well as the intellectual generalisations derived from the use of those senses, are simply laid on one side as forms of energy derived from the potentialities latent in the material body, very nearly the position indeed of modern materialism, as the term is used in psychology. This does not oppose a belief in God, who is the prime source of the powers which exist, although that is brought out more by the commentators than by Aristotle himself; nor does it infringe the doctrine of an immortal and separable soul or spirit which exists in man in addition to what we may describe as the vegetative and animal soul. It is this spirit, the rational soul which has entered from outside and exists in man alone, which is immortal. Such a doctrine sets an impassible gulf between man and the rest of creation, and explains why it is impossible for those whose thought is formed on Aristotelian lines, whether in orthodox Islam or in the Catholic Church, to admit the “rights” of animals, although ready to regard benevolent action towards them as a duty. But more, the highly abstract rational soul or spirit of the Aristotelian doctrine, void of all that could be shared with the lower creatures, and even of all that could be developed from anything that an animal is capable of possessing, is the only part of man which is capable of immortality, and such a spirit separated from its body and the lower functions of the animal soul can hardly fit in with the picture of the future life as portrayed in the Qur´an. Further, the Qur´an regards that future life as incomplete until the spirit is re-united with the body, a possibility which the Aristotelians could hardly contemplate. The Aristotelian doctrine showed the animal soul not as an invisible being but merely as a form of energy in the body: so far as it was concerned, death did not mean the going away of this soul, but the cessation of the functions of the bodily faculties, just as combustion ceases when a candle is blown out, the flame not going away and continuing to exist apart; or as the impression of a seal on wax which disappears when the wax is melted and does not continue a ghostly existence on its own account. The only immortal part of man, therefore, was the part which came to him as an emanation from the Agent Intellect, and when this emanation was set free from its association with the human body and lower soul it became inevitable to suggest its reabsorption in the omnipresent source from which it had been derived. The logical conclusion was thus a denial, not of a future life, nor of its eternity, but of the separate existence of an individual soul, and this, as we shall see, was actually worked out as a result of Arabic Aristotelianism. Thus the scholastic theologians, both of Islam and of Latin Christianity, attack the philosophers as undermining belief in individual personality and in opposing the doctrine of the resurrection, and in this latter, it must be remembered, Muslim doctrine is committed to cruder details than prevail in Christianity. But al-Farabi did not see where the Aristotelian teaching would lead him: to him Aristotle seemed orthodox because his doctrines seemed to prove the immortality of the soul.