Abu'l-Barakat al-Baghdadi

Abu'l-Barakat al-Baghdadi (about 1080 to 1164 or 1165) was a philosopher, physician and physicist of Jewish descent who served as a court physician to the caliphs of Baghdad and to Seljuk sultans, and who converted to Islam late in life, earning the honorific Awhad al-Zaman. His principal philosophical work, Kitab al-Mu'tabar, the Book of What Has Been Established by Personal Reflection, sets out a sustained critique of and alternative to the philosophy of Avicenna. In it he distinguished velocity from acceleration and argued that force is proportional to acceleration rather than velocity, a departure from Aristotelian physics, and he reconceived time as the measure of being rather than of motion. He also wrote treatises on the intellect and on astronomy, and his ideas influenced later Christian and Islamic philosophers.