Abū 'l-Barakāt al-Baghdādā (flourished in the 11th-12th centuries in Baghdad) was a scholar of the Arabic-Islamic tradition. An original philosopher and respected medical authority, he is well known by his Al-Kitāb al-Mu'tabar, a philosophical essay in which he submitted some of the fundamental concepts of natural philosophy to a penetrating analysis. He suggested in it many interesting alternatives that found an echo in modern developments in physics, such as his ideas about the physics of motion and the concept of time.
This article is the result of a close collaboration between our colleague Lutfallah Gari (Yanbu, Kingdom of Saudia Arabia) and the editorial board of www.MuslimHeritage.com (the Chief Editor).
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Figure 1: Front cover of the first volume of Abū ‘l-Barakāt’s Kitāb al-Mu’tabar (edited in Haydarabd, 1357/1938).
Abū ‘l-Barakāt al-Baghdādī was a scholar of the Arabic-Islamic tradition. Being of Jewish origin, he flourished in the 11th-12th centuries in Baghdad. An original philosopher and respected medical authority, he is well known by his Al-Kitāb al-Mu‘tabar, a philosophical essay in which he submitted some of the fundamental concepts of natural philosophy to a penetrating analysis. He suggested in it many interesting alternatives that found an echo in modern developments in physics, such as his ideas about the physics of motion and the concept of time.
The attention to his work was drawn in modern scholarship by Shlomo Pines, a scholar who devoted as early as 1938 a great attention to Abū ‘l-Barakāt’s innovative ideas in natural philosophy, especially to his Al-Kitāb al-Mu‘tabar. Pines proposed to translate this titles as “The book of what has been established by personal reflection” .
Figure 2: Shlomo Pines (1908–1990). (Source).
The following article is a concise presentation of Abū ‘l-Barakāt’s views in natural philosophy. A complete list of his extant works was generated from a number of partial lists mentioned in the modern scholarship. At the end, the article reflects ongoing debates on the issues and concepts of natural philosophy in the Arabic tradition.
Famed as Awhad al-Zamān (unique of his time), Hibat-Allāh ibn ‘Alī ibn Malkā Abū ‘l-Barakāt al-Baghdādī (ca.1077-1152) is an 11th-12th century physician and philosopher of Jewish origin. He was born in Balad, a town on the Tigris above Mosul. Precise biographical information is unavailable. We know that he was born into a Jewish family and later in life he converted to Islam. Early in his life, he had for master Abū ‘l-Hasan Sa‘īd b. Hibat Allāh and became a famous physician, serving in this quality the caliphs of Baghdad —where he resided— and the Seljuk sultans. The appellation Awhad al-Zamān, ‘the singular [personage] of his time’, probably reflects his medical rather than philosophical achievements. His formal teaching seems to have been limited to medicine, in which he had a number of students.
The anecdotes related by the biographers reveal his often difficult relations with his various patrons and their courts. Having become blind at the end of his life, he died in Baghdad probably after 560 H/1164-65 CE. Rival of the Christian physician Ibn al-Tilmīdh, he had as his disciple and friend Ishāq b. Abraham b. Ezra, who composed on him a panegyric in Hebrew. Ibn Khallīkān’s biographical dictionary describes him as ‘very presumptuous’, his hauteur being revealed in his many disputes with contemporary scholars. His involvement in philosophy seems to have been informal (even by the standards of the time) and tentative, although this led him to genial insights into natural philosophy, as it will be shown below.
A biographical compendium and complete list of the works attributed to Hibat Allāh Abū ‘l-Barakāt is given by Ibn Abī Usaybi‘a in ‘Uyūn al-‘anb ā’ fī tabaqāt al-atibbā’, where the author relates some anecdotes and sayings and lists several of al-Baghdādī’s medical works.
Despite his conversion to Islam, al-Baghdādī’s works continued to be studied at the yeshivah of Baghdad, then the centre of Jewish theology, into the 13th century. Al-Baghdādī’s commentary to the Book of Ecclesiastes continued to be copied at the same yeshivah, with full acknowledgement of its authorship. Shmu’el ben Eli, head of the yeshivah and archrival of Moses Maimonides, cites the Mu‘tabar in support of his contention that even ‘the philosophers’ are forced to admit the possibility of bodily resurrection. Ben Eli does not reveal his source; it appears to have been Maimonides’ disciple Yosef ben Yehudah who tracked down the reference .
Abū ‘l-Barakāt’s extant works include:
1. A pharmacological treatise titled Sifat Barsha‘thā (i.e. prescription of Barsha‘thā); it is about an Indian compound drug. Three copies are preserved in Turkish libraries .
2. Another pharmacological treatise titled Tiryāq amīr al-arwāh (Prince of Souls’ antidote); a manuscript copy of this text is held in Kitapsaray Library in Manisa, Turkey (MS 1781, folios 157b-159a) .
4. A treatise on the cause of the visibility of the stars at night and their invisibility at daytime, Risāla fī sabab zuhūr al-kawākib laylan wa khafā’ihā nahāran, written in answer to a question of Sultan Muhammad Tapar. In some manuscripts it is wrongly ascribed to Ibn Sīnā . It is preserved in Berlin , Hyderabad and Mashhad .
5. A treatise on using the universal (astronomical) plate (Risāla fī ‘l-‘amal bi-‘l-safīha al-‘āfāqiyyah), preserved in Niǧde, Turkey .
6. Largely unpublished is a lengthy detailed commentary on Ecclesiastes in Arabic, containing discussions of philosophical problems; it is of considerable philosophical interest. Abū ‘l-Barakāt dictated it at an advanced age to his student, the Jewish poet Ishāq b. Ibrāhīm b. ‘Azrā of Cordova . It is almost entirely unpublished, except four selected passages with translation and analysis, in Hebrew .
7. The chief work of Abu ‘l-Barakāt is undoubtedly the Kitāb al-mutabar, composed at a mature age on the basis of notes containing his philosophical reflections collected over a long period of time. Dealing with logic, physics, natural sciences, and metaphysics, it is patterned after Ibn Sīnā’s Kitāb al-Shifā, which in some parts is copied almost literally. In other parts, however, Abū ‘l-Barakāt refuted the theses of Ibn Sīnā and espoused radically different views .
Gunpowder, an invention imported from China, proved immensely popular with the warring princes of 15th-century Europe. These princes were using gunpowder in their frequent wars, to hurl large projectiles at or over the walls of towns and cities they were attacking. By the middle of the 16th century the casting and boring of cannons had progressed to a stage where serious consideration had to be given to aiming and firing of guns. All over Europe gunners began to look at ways of increasing the range and aim of their artillery.
But the path of the cannon ball made no sense within the context of Aristotelian doctrine. The Aristotelian laws of motion stated that the natural state of all ‘earthly’ objects was to be at rest. Motion away from the centre of the Earth was only possible with a ‘mover’ which had to be in contact with the object being moved. When the mover was removed, the object should fall straight down to Earth.
But cannon balls (or projectiles generally) did not fall straight down to Earth after they left the muzzle of the gun; they followed a curved path. Even the most ardent supporter of Aristotle could see that there was a flaw in the Aristotelian laws of motion. An alternative to the Aristotelian attempts to explain the motion of projectiles was the concept of the impressed force that gave rise to the famous impetus theory that was developed in Latin natural philosophy between the 14th and 16th centuries. This theory can be traced back to the critics addressed by Philoponus to the Aristotelian theory on this issue. Joannes Philoponus (ca. 490–ca. 570 CE) , also known as “John the Grammarian”, is Yūhannā al-Nahwī for the Arabic tradition. His critics were developed by Arabic scholars, including Ibn Sīnā, Abū ‘l-Barakāt al-Baghdādī and Ibn Bājja in the 12th-century Andalus. According to the theory of impressed force, an incorporeal motive force that is imparted to the projectile causing it to continue moving .
Building on the views of Philoponus and Ibn Sīnā, Abū ‘l-Barakāt accepts, though with modifications, the theory according to which the cause of this movement is a ‘violent inclination’, that is to say a force imparted by the projecting body to the projectile . This type of force is similar to, or identical with, the one indicated by the term impetus that was coined by the French philosopher and scientific theorist Jean Buridan (1300-1358) . Abū ‘l-Barakāt, like Ibn Sīnā, subscribes to the doctrine positing a “violent inclination” (mayl qasrī in Arabic). “Violent inclination” is opposed to the “natural inclination” in virtue of which bodies removed from their natural place tend to return to it; it is regarded as having been imparted by the mover to a body in a state of violent motion (for instance, to a stone thrown upward or to an arrow shot from a bow). The notion of violent inclination is used to account for the continuation of violent motion after the separation of the projectile from the mover. Like Buridan, and contrary to Ibn Sīnā, Abū ‘l-Barakāt regards “violent inclination” as self-expending; it is used up in the very process of violent motion .
The works of Ibn Sīnā, Abū al-Barakāt al-Baghdādi, Ibn Bājja and others led to the development of the idea of impetus and momentum in Galileo’s physics in the 17th century .
The acceleration of the motion of falling bodies is attributed by Abū ‘l-Barakāt to two causes:
(1) He holds that a violent and a natural inclination can simultaneously coexist in a projectile. Thus, when a body begins to fall, a residue of violent inclination still subsists in it and opposes the natural inclination that causes the body to descend, slowing down its fall. The acceleration of the fall is due to the gradual weakening of the violent inclination.
(2) The second cause of the acceleration of the motion of falling bodies is that the force (i.e., gravity) generating natural inclination resides in the falling body and produces a succession of natural inclinations in such a way that the strength of the inclination increases throughout the fall.
Abū ‘l-Barakāt’s conception of the second cause seems to anticipate the fundamental law of classical mechanics, according to which a continually applied force produces acceleration. This is contrary to the Aristotelian doctrine of natural philosophy which assumes that such a force produces a uniform motion .
He explains the acceleration in the fall of heavy objects by the fact that the principle of natural inclination (mayl tabī‘ī, a philosophical term developing to a large extent the Greek famous rhope)  contained in them, furnishes them with successive inclinations. In the trend of the commentaries in natural philosophy inspired by Philoponus, it seems that the text of the Mu‘tabar treating of this doctrine is the first one, as far as is known at present, where one finds implied this fundamental law of modern dynamics: a constant force gives rise to an accelerated movement .
Abū ‘l-Barakāt al-Baghdādī had many new ideas concerning the physics of motion. In addition to the law of acceleration, he suggested that motion is relative, that is, that there is motion only if the relative positions of the bodies in question change. These ideas are highlighted here because of their resemblance to modern thoughts on the same subjects. The Kitāb al-Mu‘tabar contains many other, no less innovative, ideas that have a modern counterpart; for example, the claim that each type of body has a characteristic velocity that reaches its maximum when its motion encounters no resistance. Although al-Mu‘tabar is not a systematic work, comprising instead notes on various subjects that al-Baghdādī wrote for himself over the years, Pines showed that the paramountcy of a priori knowledge underlies many of the work’s criticisms and innovations .
As mentioned above, Abū ‘l-Barakāt has some quotations from al- Shifā’ of Ibn Sīnā; but on the whole he differs from Ibn Sīnā in formulation and phrasing, often also in opinion. He says that phenomena such as shooting stars, comets, the halo and the rainbow cannot be explained by terrestrial causes only, but that in fact they are caused and maintained by celestial forces . The same holds for wind: it is air moved by celestial forces . Furthermore, he disagrees with Ibn Sīnā and Aristotle about the explanations of the formation of hail , rivers  and thunder . The Milky Way is a phenomenon of the celestial world, not of the upper atmosphere, as Aristotle thinks . On the whole, as pointed out by researchers, the account of Abū ‘l-Barakāt is quite original and independent .
The interplay between words and concepts is given particular attention in the al-Mu‘tabar. For example, al-Baghdādī developed his strikingly innovative theory of time after reaching the conclusion that the word “time” as used in everyday speech stands for a very fundamental concept, the true nature of which has been obscured by scholastic analysis. According to Langermann, perhaps most interesting among al-Baghdādī’s achievements is his reappraisal of the idea of time. Dissatisfied with the regnant approach, which treated time as an accident of the cosmos, he drew the conclusion that time is an entity whose conception (ma‘qūl al-zamān) is a priori and almost as general as that of being, encompassing the sensible and the non-sensible, that which moves and that which is at rest. Our idea of time results not from abstraction, stripping accidents from perceived objects, but from a mental representation based on an innate idea. Al-Baghdādī stops short of offering a precise definition of time, stating only that “were it to be said that time is the measure of being (miqdār al-wujūd), that would be better than saying [as Aristotle does] that it is the measure of motion”. His reclassification of time as a subject for metaphysics rather than for physics represents a major conceptual shift, not a mere formalistic correction. It also breaks the traditional linkage between time and space. Concerning space, al-Baghdādī held unconventional views as well, but he did not remove its investigation from the domain of physics .
In his physics, Abū ‘l-Barakāt employs a method similar to the one he utilized in his psychology. Like his 10th-century predecessor al-Rāzī (by whom he may have been influenced, although there is no evidence either way) and in contrast with the Aristotelians, he relies in his physical theories, just as he does in his doctrine of the soul, on what he regards as self-evident, i.e., immediately perceived truths that are not dependent upon empirical data. Applying this method, he rejects the Aristotelian contention that time is the measure of movement. He denies the Aristotelian theory of space, the existence of a three-dimensional space. With John Philoponus he refutes the proposition denying the possibility of movement in the void. Having demonstrated the fallacy of the peripatetic arguments to the contrary, he proves the infinity of space by the impossibility for man to conceive a limited space. In effect, he shows that the apperception of time, of being, and of self, is anterior in the soul to any other apperception the soul might have, and that the nature of being and that of time are closely linked. According to his definition, time is the measure of being (not, as the peripatetics held, that of movement). He does not admit the diversity of the various levels of time, the gradations of zamān, dahr, sarmad assumed by Ibn Sīnā and other philosophers. In his opinion, time characterizes the being of the Creator as well as that of created things. He identifies prime matter with the body considered merely from the point of view of corporality, apart from any other characteristic; corporality being an extension susceptible of being measured. Among the four elements, earth alone is, in his view, constituted of corpuscles, indivisible because of their solidity .
According to him, the notion of time is ontologically prior to the notion of movement. Nor does he regard time as being merely a subjective phenomenon. It is in fact the measure of Being, and as such it should not be regarded as external to Being. Comparisons between the lengths of two or more durations are, however, due to a mental comparison between the two .
 Pinès Salomon [Shlomo Pines], “Les précurseurs musulmans de la théorie de l’impetus”, Archeion (Paris), vol. 21 (1938): pp. 298-306; “Etudes sur Awhad az-Zamān Abū l-Barakāt al-Baghdādī “, Revue des Etudes Juives vol. 3 (1938), pp. 3-64; vol. 4 (1938): pp. 1-33; “Quelques tendances anti-péripatéticiennes de la pensée scientifique islamique” Thalès (Paris) vol. 24 (1940): pp. 210-219; “Un précurseur Baghdadien de la théorie de l’impetus”, Isis vol. 44 (1953): pp. 247-251. Those studies were reprinted in Shlomo Pines, Collected Works. 2 vols. Leiden: Brill, 1979-86.
 Khayr al-Dīn Al-Ziriklī, “Awhad al-Zamān” in Al-A’lām, Beirut, vol. 8; Wilferd Madelung, “Abū ‘l-Barakāt al-Bagdādī”, Encyclopedia Iranica, vol. 1, pp. 226-228; Shlomo Pines, “Abu ‘l- Barakāt Hibat Allāh b. Malkā al-Baghdādī al-Baladī”, Encyclopaedia of Islam (2nd ed.), vol. 1, p. 111; Y. Tzvi Langermann, “Al-Baghdadi, Abu ‘l-Barakat (fl. c.1200-50)“, Routledge Encyclopedia of Philosophy, New York: Routledge Publishers, 1998, reproduced on www.muslimphilosophy.com (accessed 17 June 2008); Jon McGinnis, “Arabic and Islamic Natural Philosophy and Natural Science“, on Stanford Encyclopedia of Philosophy (first published 19 December, 2006, accessed online 17 June 2008).
 Albert Dietrich: Medicinalia Arabica: Studien über arabische medizinische Handschriften in türkischen und syrischen Bibliotheken, Göttingen: Vandenhoeck & Ruprecht, 1966, ss. 217, 228-229; Ahmed Ateş: “Arabic Manuscripts in the Libraries of Anatolia” (in Arabic), Revue de l’institut des manuscrits arabes, tome 4, 1958, pp. 33-35; Ramadan Şeşen et al., Catalogue of Islamic Medical Manuscripts in the Libraries of Turkey, Istanbul: Research Center for Islamic History, Art and Culture, 1984, pp. 90-91.
 Dietrich, op.cit., pp. 229-230; A. Ateş: “Arabic Manuscripts in the Libraries of Anatolia”, op. cit.
 M. T. Dānešpažūh, Fehrest-e mīkrūfilmhā-ye Ketābkāna-ye Markazī-e Dānešgāh-e Tehrān, Tehran, 1348 Š./1969, p. 609, cited by Wilferd Madelung, ‘Abū’l-Barakāt al-Bagdādī’, Encyclopedia Iranica, vol. 1 (1987), pp. 226-228.
 Carl Brockelmann, Geschichte der arabischen Litteratur, the Arabic translation, Cairo: The Egyptian General Organization of Books, vol.9 (Section 5), 1995, pp. 72-73.
 Translated by E. Wiedemannn in Eders Jahrbuch für Photographie 1909, pp. 49-54; see W. Madelung, op. cit. See also S. Pines, “Abū ‘l- Barakāt al-Baghdādī”, Encyclopaedia of Islam (2nd ed.), op. cit.
 Brockelmann, Geschichte der arabischen Litteratur, op. cit.
 Boris A. Rosenfeld & Ekmeleddin Ihsanoglu, Mathematicians, Astronomers, and Other Scholars of Islamic Civilization and their Works (7th-19th Centuries), Istanbul: Research Center for Islamic History, Art and Culture, 2003, p. 184.
 S. Pines, “Abū ‘l-Barakat Al-Baghdadi”, Encyclopaedia of Islam, op. cit.; W. Madelung, op. cit.
 S. Pines, “Abū ‘l-Barakat Al-Baghdadi”, Encyclopaedia of Islam, op. cit.; W. Madelung, op. cit.; Langermann, “Al-Baghdadi, Abū ‘l-Barakat”, op. cit. Kitāb al-Mu‘tabar is edited in three volumes by Şerefettin Yaltkaya, Hyderabad: Osmania Publication Bureau, 1357-58/1939-40.
 Prabhakar Gondhalekar, The Grip of Gravity: The Quest to Understand the Laws of Motion and Gravitation, Cambridge: Cambridge University Press, 2001, pp. 51-52. See also the works of Pines quoted in footnote 1. The most up-to-date source on this issue is Paul Lettinck, Aristotle’s Physics and its Reception in the Arabic World. With an Edition of the Unpublished Parts of Ibn Bājja’s Commentary on the Physics. Leiden: Brill, 1994.
 S. Pines, “Abū ‘l-Barakāt al-Baghdādī”, Encyclopaedia of Islam, op. cit.
 P. Gondhalekar, The Grip of Gravity, op. cit.
 Shlomo Pines, “Abū ‘l-Barakāt al-Baghdādi”, Dictionary of Scientific Biography, New York: Scribners Publishers, vol. 1 (1970), pp. 26-28.
 The classical study tracing the fate of the Arabic contributions to the genesis of the impetus theory is Ernest A. Moody, “Galileo and Avempace: The Dynamics of the Leaning Tower Experiment”, Journal of the History of Ideas vol. 12 (2) (April 1951), pp. 163-193; vol. 12 (3), pp. 375-422. See also Paul Lettinck, Aristotle’s Physics and its Reception in the Arabic World, op. cit., “Epilogue”: “The influence of Arabic philosophers on the development of dynamics in the Middle Ages”, pp. 665-673; and Abel B. Franco, “Avempace, Projectile Motion, and Impetus Theory”, Journal of the History of Ideas vol. 64, No. 4 (October 2003), pp. 521-546.
 S. Pines, “Abū ‘l-Barakāt al-Baghdādī”, Dictionary of Scientific Biography, op. cit.
 On this important subject, see M. Abattouy, “Greek Mechanics in Arabic Context: Thābit ibn Qurra, al-Isfizārī and the Arabic Traditions of Aristotelian and Euclidean Mechanics”, Science in Context (Cambridge University Press) vol. 14, No. 1-2, (2001): pp. 179–247; pp. 203-205.
 S. Pines, “Abū ‘l-Barakāt al-Baghdādī”, Encyclopaedia of Islam, op. cit.
 Paul Lettinck: Aristotle’s Meteorology and its Reception in the Arab World, Leiden: Brill, 1999, pp. 83-85.
 Ibid, pp. 183-184.
 Ibid, pp. 114-115.
 Ibid, pp. 146-147.
 Ibid, p. 237.
 Ibid, p. 85.
 Ibid, p. 11.
 S. Pines, “Abū ‘l-Barakāt al-Baghdādī”, Dictionary of Scientific Biography, op. cit.; S. Pines, “Abū ‘l-Barakāt al-Baghdādī”, Encyclopaedia of Islam, op. cit.
 S. Pines, “Abū ‘l-Barakāt al-Baghdādī”, Dictionary of Scientific Biography, op. cit.