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Hibat Allah Abu'l-Barakat al-Baghdaadi (c. 1080-1165) was an Islamic philosopher, physicist, psychologist, physician and scientist of Jewish-Arab descent from Baghdad, Iraq. His Hebrew birth name was Nathanel. It is known that Abu-l-Barakat had converted from Judaism to Islam at some point in his life.[1] His thought influenced the Illuminationist school of classical Islamic philosophy, the medieval Jewish philosopher 'Izz ad-Dawla Ibn Kammuna,[2] and the Christian philosophers Jean Buridan and Albert of Saxony.[3]


Experimental method

Al-Baghdaadi described an early scientific method emphasizing repeated experimentation, influenced by Avicenna, as follows:[4]

"Because of the frequency of the experience, these judgements may be regarded as certain, even without our knowing the reason [for the phenomenon]. For there is certain knowledge that the effect in question is not due to chance. It must accordingly be supposed that it is due to nature or to some modality thereof. Thus the cause qua cause, though not its species or mode of operation, is known. For experimental science is also constituted by a knowledge of the cause and by an induction based on all the data of sensation; whereby a general science is reached. ... But in the cases in which an experiment has not been completed, because of its not having been repeated in such a way that the persons, the time and the circumstances varied in everything that did not cause the determining cause, whereas this cause [remained invariable], the experiment does not prove certain knowledge, but only probably opinion."

Kitab al-Mu'tabar

He wrote a critique of Aristotelian philosophy and Aristotelian physics entitled Kitab al-Mu'tabar, in which he developed concepts which resemble several modern theories in physics.[2]



According to Alistair Cameron Crombie, al-Baghdaadi was a follower of Avicennism, who

proposed an explanation of the acceleration of falling bodies by the accumulation of successive increments of power with successive increments of velocity.[5]

According to Shlomo Pines, al-Baghdaadi's theory of motion was thus

the oldest negation of Aristotle's fundamental dynamic law [namely, that a constant force produces a uniform motion], [and is thus an] anticipation in a vague fashion of the fundamental law of classical mechanics [namely, that a force applied continuously produces acceleration].[6]

Al-Baghdaadi's theory of motion was vaguely foreshadowing Newton's second law of motion, by distinguishing between velocity and acceleration and for showing that force is proportional to acceleration rather than velocity.[3][7] The 14th-century philosophers Jean Buridan and Albert of Saxony later refer to Abu'l-Barakat in explaining that the acceleration of a falling body is a result of its increasing impetus. Abu'l-Barakat also modified Avicenna's theory of projectile motion, and stated 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.[3]

Al-Baghdaadi also suggested that motion is relative, writing that "there is motion only if the relative positions of the bodies in question change." This vaguely foreshadows the concept of relativity, in recognizing the idea of there being different frames of references. Another theory he developed which has no modern counterpart is his theory that "each type of body has a characteristic velocity that reaches its maximum when its motion encounters no resistance."[2]

Space and Time

Al-Baghdaadi criticized Aristotle's concept of time as "the measure of motion" and instead redefines the concept with his own definition of time as "the measure of being", thus distinguishing between space and time, and reclassifying time as a metaphysical concept rather than a physical one. The scholar Y. Tzvi Langermann writes:[2]

Dissatisfied with the regnant approach, which treated time as an accident of the cosmos, al-Baghdadi drew the conclusion that time is an entity whose conception (ma'qul al-zaman) 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-Baghdadi stops short of offering a precise definition of time, stating only that 'were it to be said that time is the measure of being (miqdar al-wujud), 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-Baghdadi held unconventional views as well, but he did not remove its investigation from the domain of physics.


On his contributions to Islamic psychology, Langermann writes:[2]

Al-Baghdadi's most significant departure in psychology concerns human self-awareness. Ibn Sina had raised the issue of our consciousness of our own psychic activities, but he had not fully pursued the implications for Aristotelian psychology of his approach. Al-Baghdadi took the matter much further, dispensing with the traditional psychological faculties and pressing his investigations in the direction of what we would call the unconscious.


  1. ^ Routledge History of Philosophy By Stuart Shanker, John Marenbon, George Henry Radcliffe Parkinson, pg. 76
  2. ^ a b c d e Langermann, Y. Tzvi (1998), "al-Baghdadi, Abu 'l-Barakat (fl. c.1200-50)", Islamic Philosophy, Routledge Encyclopedia of Philosophy,, retrieved 2008-02-03 
  3. ^ a b c Gutman, Oliver (2003), Pseudo-Avicenna, Liber Celi Et Mundi: A Critical Edition, Brill Publishers, p. 193, ISBN 9004132287 
  4. ^ Shlomo Pines (1986), Studies in Arabic versions of Greek texts and in mediaeval science, 2, Brill Publishers, p. 339, ISBN 9652236268 
  5. ^ Alistair Cameron Crombie, Augustine to Galileo 2, p. 67.
  6. ^ Pines, Shlomo (1970). "Abu'l-Barakāt al-Baghdādī , Hibat Allah". Dictionary of Scientific Biography. 1. New York: Charles Scribner's Sons. pp. 26–28. ISBN 0684101149. 
    (cf. Abel B. Franco (October 2003). "Avempace, Projectile Motion, and Impetus Theory", Journal of the History of Ideas 64 (4), p. 521-546 [528].)
  7. ^ Shlomo Pines (1986), Studies in Arabic versions of Greek texts and in mediaeval science, 2, Brill Publishers, p. 203, ISBN 9652236268 


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