Over time, the translation movement stated by the ‘Abbāsid Caliph al-Manṣūr (714–775) translated a large part of the works of Aristotle into Arabic. His philosophy was warmly welcomed by the Islamic philosophers, who didn’t just read it but analysed it with great care and wrote long and deep commentaries on it. The works of Aristotle were from this source reintroduced into Europe in the twelfth century, together with the, often critical, commentaries of the Islamic scholars, this time translated from Arabic into Latin, sometimes via Hebrew. This led, thanks largely to the work of Albertus Magnus (c. 1200–1280) and his pupil Thomas Aquinas (c. 1225–1274), to the acceptance of Aristotle on the then still comparatively young, medieval European universities and the beginnings of scholasticism. All of this, of course, lies in the future and we first want to look at how Islamic scholars accepted and reacted to Aristotle’s theories of motion, fall and projectile motion. This reception was influenced by the writings on the subject of John Philoponus (c. 490–c. 570), which had also been translated into Arabic, and which, whilst largely ignored in late antiquity and the early European Middle Ages, enjoyed a strong reception under Islamic scholars.
Working our way forward chronologically, our first Islamic scholar who took up the works of Aristotle was Abū Naṣr Muḥammad al-Fārābī (c. 870–950/951), known in Latin as Alfarabius. al-Fārābī, a polymath, was born in Trasoxiana (modern Turkestan) the son of a military soldier.
Whether his was Turkic or Persian is not known. Little is known of his childhood but he went to Harran to study under the Nestorian Christian Yuhanna ibn Haylan. Later he moved to Baghdad to continue his studies under Ibn Haylan and also studied logic with Abu Bishr Matta ibn Yunus (d. 940) and Arabic grammar with Abu Bakr ibn al-Sarraj (c. 875–c. 928).
Later in life he moved to Damascus and then to Alexandria before returning to Damascus, which is where he probably died. His importance for the history of physics is not direct. However, he attempted to reconcile the philosophies of Plato and Aristotle in the tradition of the Neoplatonists. Drawing attention to their works for other Islamic scholars. In his work he provided the first comprehensive Arabic classification of the sciences in his Kitab al-ibsa al ‘Ulum (Catalog of Sciences). It is a largely Aristotelian in nature and was adopted, amongst others, by Ibn al-Haytham (c. 965–1039) and Ibn Rushd (1126–1198). His only direct contribution to physics was a new argument in his On Vacuum on the nature of the existence of void, concluding that air’s volume can expand to fill available space, and he suggested that the concept of perfect vacuum was incoherent.
Our next Islamic scholar is Abū Rayhān Muhammad ibn Ahmad al-Bīrunī (973–after 1050) possibly the most polymathic of all Islamic scholars.
He was born in an outlying district of Kath the capital of the Afrighid Kindom of Khwarazm, part of the Persian Empire before it was conquered by the Muslims, now in Uzbekistan. Depending who is doing the describing he is described as Khwarezmian, Persian, or Uzbeki. He led a very complex life, which would turn this post into a book if I tried to describe it. He is reputed to have written 146 books on a very wide range of subjects., although his main areas of study were astronomy, mathematics, and geography. He lived for a time in India studying the land, its cultures, and its peoples. The book he wrote on India is his most well-known work. His only real contribution to physics was his use of a hydrostatic balance to experimentally determine the density of many different substances. “He reports very precise specific gravity determinations for eight metals, fifteen other solids (mostly precious or semiprecious stones), and six liquids.” (DSB). He carried out a major dispute with Ibn Sīnā (980-1073) in which he rejected Aristotle’s claim that the Earth is eternal.
Abū ʿAlī al-Ḥusayn bin ʿAbdullāh ibn al-Ḥasan bin ʿAlī bin Sīnā al-Balkhi al-Bukhari (980-1073), known in Latin as Avicenna, was one of the most influential of all Islamic philosophers within the Islamic Empire and one of the two most important Islamic philosophers, when translated into Latin during the twelfth century Scientific Renaissance. Born into a Persian family in Transoxiana near the city of Bukhara, today in Uzbekistan. He had a comprehensive and wide-ranging education and became a physician.
Although he wrote books on almost all subjects, his two most important works are Kitāb al-Shifāʾ (The Book of Healing) an encyclopaedia of science and philosophy, intended to cure the souls and the five volume al-Qānūn fī al-Ṭibb (The Canon of Medicine) and encyclopaedia of medicine. The latter an Aristotelean take on the works of Hippocrates and Galen became a standard work in Europe during the Middle Ages and Renaissance and was still in use in the seventeenth century. Avicenna’s philosophical work, a Neoplatonic Aristotelianism came to overshadow and replace the philosophical work of al-Fārābī, Farabism.
In The Book of Healing, probably influenced by John Philoponus, Ibn Sīnā developed a theory of motion in which he distinguished between the inclination or tendency to motion and the force of a projectile. Projectile motion was the result of an inclination (mayl) transferred to the projectile by the thrower. He concluded that projectile motion in a vacuum would not cease. For him inclination was a permanent force whose effect was dissipated by external forces such as air resistance.
Abu’l-Barakāt Hibat Allah ibn Malkā al-Baghdādī (c. 1080–1164) was born Baruch ben Malka into a Jewish family in Balad on the Tigris north of Mosul in modern Iraq. He only converted to Islam late in life. He is regarded as a follower of Ibn Sīnā and was like him a physician. He was an Aristotelian but heavily criticised Aristotle’s theories of motion.
He showed, in his theories, that velocity and acceleration are two different things and that force is proportional to acceleration and not velocity. He “proposed an explanation of the acceleration of falling bodies by the accumulation of successive increments of power with successive increments of velocity. ( A. C. Crombie Augustine to Galileo v.2, p.67). He further developed Philoponus’ theory of impetus, stating that the mover imparts a violent inclination (mayl qasri) on the moved and that this diminishes as the moving object distances itself from the mover. ( Gutman, Oliver (2003), Pseudo-Avicenna, Liber Celi Et Mundi: A Critical Edition, Brill, p. 193) He further suggested that “there is motion only if the relative positions of the bodies in question change.” He also stated that “each type of body has a characteristic velocity that reaches its maximum when its motion encounters no resistance. ( Langermann, Y. Tzvi, “al-Baghdadi, Abu ‘l-Barakat (fl. c.1200-50)”, Islamic Philosophy, Routledge Encyclopedia of Philosophy 1998) ,
Abū Bakr Muḥammad ibn Yaḥyà ibn aṣ-Ṣā’igh at-Tūjībī ibn Bājja (c. 1085–1138), known in Latin as Avempace, was an Arab born in Zaragoza in al-Andalus, today’s Spain. Another polymath he made important contribution to botany in his Kitāb an-Nabāt (“The Book of Plants”).
Much of what we know about his theories of motion comes from the extensive criticism of them by Ibn Rushd, (1126–1198). The philosopher Ernest A. Moody identifies four main reasons for regarding Ibn Bājja as a major figure in the development of the theory of impetus:
1. “For Avempace…V = P – M, so that when M = 0, V = P. This opposes Aristotle’s (supposed use of) V = P / M.”
2. “Internal coherence with this “law of motion” requires, Moody believes, also a defence of the theory of an impressed force – as we find for example in Philoponus himself.”
3. “Avempace’s appeal to an ‘impressed force’ was also reflected in the fact that ‘if we use modern terms, it might be said that the force of gravity, for Avempace, is not determined essentially as a relation between the masses of different bodies, but is conceived as an absolute indwelling power of self-motion animating the body like a soul.”
4. “The theory of an ‘impressed force’ appears to have been upheld by al-Bitruji, who was influenced ins ideas by Avempace’s disciple Ibn-Tofayl.”
Ibn Bājja argued that even in a void a body would move with finite velocity because, although there was no resistance, the body would still have to traverse distance. (( A. C. Crombie Augustine to Galileo v.2, p.67).
We turn briefly to ʾAbū Bakr Muḥammad bin ʿAbd al-Malik bin Muḥammad bin Ṭufayl al-Qaysiyy al-ʾAndalusiyy (c. 1105–1185), Latin Abubacer Aben Tofail. Born in al-Andalus in Guadix near Granada into an Arabic family, he was as stated above in 4. a student of Ibn Bājja. He is notable for having agitated to reject Ptolemaic astronomy and return to a purer Aristotelian homocentric astronomy.
Ibn Tufayl in turn influenced Nur al-Din Ibn Ishaq al-Betrugi (died c. 1204), known in Latin as Alpetragius, about whom almost nothing is known except that he probably came from near Cordoba. He adopted both an impetus theory of projectile motion and an Aristotelian homocentric astronomy model from Ibn Tufayl, combining the two to suggest, like Philoponus, impetus as the form of motion of the planets.
Ibn Tufayl was heavily involved in politics and was a secretary for the ruler of Granada, and later as vizier and physician for Abu Yaqub Yusuf (1135–1184), the Almohad caliph. The Almohad Caliphate ruled over Southern Spain and Northern Africa from 1121 to 1269. Ibn Tufayl named Abū l-Walīd Muḥammad Ibn ʾAḥmad Ibn Rushd; (1126–1198), Latin Averroes. Ibn Rushd was together with Ibn Sīnā the second of the two most important Islamic philosophers, when translated into Latin during the twelfth century Scientific Renaissance.
Ibn Rushd was born in Cordoba into a family well known in the city for their public service, especially in the legal and religious fields. He was probably of mixed Muladí and Berber ancestry. The Muladí were the native population of the Iberian Peninsula before the Muslim conquest. He was a strict adherent of Aristotelian philosophy rejecting the Neoplatonic interpretations of al-Farabi and Ibn Ibn Sīnā. He came to be regarded as the greatest of the Islamic Aristotelians and acquired the title of The Commentator in medieval Europe.
He followed Ibn Tufayl in rejecting the deferent and epicycle models of Ptolemy in favour of the homocentric spheres of Aristotle. However, he also rejected the impetus theory that Ibn Tufayl had inherited from Ibn Bājja.
In his commentary on Aristotle’s Physics, Ibn Rushd launches a detail attack on Ibn Bājja’s theory of motion, which includes quotes from Ibn Bājja’s lost work on physics. This debate between the two theories, Aristotle contra Philoponus, as presented by Ibn Rushd was taken up again in Europe in the thirteenth century as part of the Scientific Renaissance with European medieval scholars taking up arms respectively for Averroes or Avempace.
All of these Islamic polymathic philosophers, spread out over nearly two centuries, had the philosophy of Aristotle at the core of their own work. The majority, however, in a modified Neoplatonic version. When dealing with Aristotle’s concepts of motion, the ideas of John Philoponus came to play a central modifying role, with the notable exception of the work of Ibn Rushd. Through the discussion and adoption of Philoponus’ proto-impetus theory meant that when the big twelfth century, Scientific Renaissance translation movement was up and running this alternative to Aristotle’s concepts became once again available in medieval Europe.