Abu'l-Barakāt al-Baghdaadi, famed as Awhad al-Zamān (Unique One of his Time), was born in Balad, a town on the Tigris above Mosul in modern-day Iraq.
As a renowned physician, he has served at the courts of the caliphs of Baghdad and the Seljuq sultans.
He has converted to Islam in old age.
Abu'l Barakat does not refer to his conversion in his writings, and the historical sources give contradictory episodes of his conversion.
According to the various reports, he had converted either out of "wounded pride", fear of the personal consequences of the death of Sultan Mahmud's wife while under his care as a physician or fear of execution when he was taken prisoner in a battle between the armies of the caliph and that of the sultan.
Isaac, the son of the Abraham Ibn Ezra and the son-in-law of Judah Halevi, was one of his pupils, to whom Abu'l-Barakāt, Jewish at the time, dictated a long philosophical commentary on Ecclesiastes, written in Arabic using Hebrew aleph bet.
Isaac wrote a poem in his honor as introduction to this work Al-Baghdaadi described an early scientific method emphasizing repeated experimentation, influenced by Ibn Sina.
Al-Baghdaadi's theory of motion distinguished between velocity and acceleration and showed that force is proportional to acceleration rather than velocity.
The 1fourteenth-century philosophers Jean Buridan and Albert of Saxony will 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 Ibn Sina'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.
Al-Baghdaadi also suggested that motion is relative, writing 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."
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.
He upheld the unity of the soul, denying that there is a distinction between it and the intellect.
For him, the soul's awareness of itself is the definitive proof that the soul is independent of the body and will not perish with it.
He wrote a critique of Aristotelian philosophy and Aristotelian physics entitled Kitab al-Mu'tabar (the title may be translated as "The Book of What Has Been Established by Personal Reflection").
According to Abu'l-Barakāt, Kitāb al-Muʿtabar consists in the main of critical remarks jotted down by him over the years while reading philosophical text, and published at the insistence of his friends, in the form of a philosophical work.
The work "presented a serious philosophical alternative to, and criticism of, Ibn Sina".
He also developed concepts which resemble several modern theories in physics.
He dies in 1165 in Baghdad.
Abu'l-Barakāt's thought had a deep influence on Islamic philosophy but none on Jewish thought.
His works are not translated into Hebrew, and he is seldom cited in Jewish philosophy, probably because of his conversion to Islam.
