According to Alistair Cameron Crombie, al-Baghdadi proposed an explanation of the acceleration of falling bodies by the accumulation of successive increments of power with successive increments of velocity. According to Shlomo Pines, al-Baghdadi'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]. Al-Baghdadi's theory of motion distinguished between velocity and acceleration and showed that force is proportional to acceleration rather than velocity. 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 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. Al-Baghdadi 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." Space and time Al-Baghdadi 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: In his view, there is just one time which is similar for all beings, including God. Abu'l-Barakāt also regarded space as three-dimensional and infinite. Psychology 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. On his contributions to Islamic psychology, Langermann writes: Works 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