and they sometimes use these expressions to define motion. They hold two views on whether motion of any kind subsists in the Lord, Most High. Aristotle’s followers restricted motion to bodies, yet they describe the soul as having a kind of motion, although they do not regard it as a body; thus they contradict themselves. They recognized “three types” of motion, but Ibn Sīnā added a fourth category, bringing the total to “four.”
They treat motion as a genus comprising several species: motion in quality, motion in quantity, motion in position, and motion in place.
“Motion in quality” is a thing’s transformation from one quality to another: for example, its becoming black, red, green, or yellow; its becoming sweet or sour; or a change in its smell. The same applies to souls: a person’s acquiring knowledge after ignorance, loving after hating, believing after disbelieving, rejoicing after sorrow, or becoming pleased after anger. All these states of the soul constitute motion in quality. This is among the arguments used by those philosophers who considered motion possible with respect to Him, for, according to them, His willing to bring something into being is motion.
“Motion in quantity” includes a thing’s extension: for example, an animal growing larger after being small and longer after being short, or the growth of trees and plants, with their roots extending into the earth and their branches into the air. This is motion in magnitude and quantity, just as the former is motion in attributes and quality.