This is a science that investigates bodies from the point of view of the motion and stationariness which attach to them. It studies the heavenly and the elementary bodies (substances), as well as the human beings, the animals, the plants, and the minerals created from them. It also studies the springs and earthquakes that come into being in the earth, as well as the clouds, vapors, thunder, lightning, and storms that are in the atmosphere, and other things. It further studies the beginning of motion in bodies - that is, the soul in the different forms in which it appears in human beings, animals, and plants.
The books of Aristotle on the subject are available to scholars. They were translated together with the other books on the philosophical sciences in the days of al-Ma'mun. Scholars wrote books along the same lines and followed them up with explanation and comment.715 The most comprehensive work written on the subject is Avicenna's Kitab ashShifa'. In it, Avicenna treats all the seven philosophical sciences, as we have mentioned before. 716 Avicenna later on abridged the Kitab ash-Shifa' in the Kitab an-Najah and the Kitab al-Isharat. In a way, he opposed Aristotle on most (physical) problems and expressed his own opinion on them. Averroes, on the other hand, abridged the books of Aristotle and commented on them, but followed him and did not oppose him. Scholars have written many works on the subject, 717 but these are the works that are famous at this time and to which attention is paid when one (studies) the craft (of physics).
The people of the East are concerned with Avicenna's Kitab al-Isharat. The imam Ibn al-Khatib wrote a good commentary on it. The same was done by al-Amid! 718 Another commentary on the work was written by Nasir-ad-din at-Tusi,719 who is known as Khawajah (Khoja), an 'Iraqi scholar. He investigated many of the problems (of the Isharat) and compared what the imam (Ibn al-Khatib) had to say about them. He went beyond (Ibn al-Khatib's) studies and investigations.
"And He knows more than any scholar." 720