Compendium of All Natural Science

22. How motion is found in three principles.

From those things which we have said, it can be gathered that motion is found chiefly in three principles: quantity, quality, and place. For that is true motion whose extremes are contained within some principle. Whence it happens that neither generation nor corruption seem to be motion in the proper sense: since generation indeed begins from that which is not, while corruption, on the contrary, ends in that which is not. Moreover, that motion which is from quality to quality is found only in 그hat species which the Greeks call natural power, or in that which they call passible quality. Yet not in all of these; for light can be introduced without any motion.

23. That the final parts of motion are assigned in actuality, but the beginnings not likewise.

Just as a line, in that part where it begins and is terminated, will contain points in actuality, but since the intermediate parts are infinite, they exist only in potentiality: so too motion will be said to have produced its first and intermediate parts in potentiality, but its final parts in actuality. For although there is no first change—since motion preceded any motion whatsoever—nevertheless a final part is assigned.

24. On the generation of motions, or rather their difference according to efficient causes.

Of motions, some occur by force, some by the impulse of nature, others when from the soul