On Metaphysics

It has already been demonstrated in natural science that everything that is moved presupposes a moving principle; that, furthermore, the moved is moved only in so far as it exists potentially and that the mover carries out a movement in so far as he is in actu; and that the mover, if one time he carries out a movement but the next time does not produce such, must, in a certain manner, be passively moved, since active motion exists only potentially in him if he does not actually move. If we thus assume in this case that the first mover of the world one time carries out a movement, but not the next time, then we have to conclude inevitably that a further mover, prior to this one, must exist in the world. This one is, therefore, not the prime mover. Now, if we thus assume in the case of the second one that he moves one time and does not move the next time, we necessarily get the same result with respect to it as we got in the first case. Therefore, it is an irrefutable consequence that either this succession yields an infinite chain or that we admit that in the "here" [i.e., the world] there exists a mover who is in no manner moved nor may yet be moved, neither as concerns his essence, nor yet per accidens. Since matters lie thus, this mover is consequently of necessity eternal; the object that is put in motion by him is likewise eternally in motion; for if something existed that, at a given time, were potentially in a position to be moved by the eternal mover, then a mover who would precede the eternal mover, would inevitably have to exist "beyond." For this reason, the mover whose existence has been demonstrated in the 16th Book of Zoology, would not possess the qualification sufficient for carrying out a special movement without the aid of the mover of the whole world.

If it is thus clear that an eternal motion exists in the "here," and if it is impossible that there is an eternal motion, leaving out of account the circular and spatial one -- this has been discussed in natural science -- then it is evident that this demonstration yields the necessity of an eternal, spatial motion existing in the "here." However, this is in no manner ascertainable by sensual perception, if you except the motion of the heavenly body. The motion of this body must, therefore, be the eternal motion of which we are in search. The mover of this body is at the same time the eternal mover whose existence has become intelligible through former discussions. The existence of an eternal, continuous motion with respect to time has likewise been proved; for, time, as has been demonstrated, is one of the accidents of motion. Time cannot be slowly composed, not even by him who is raised above time. The reason for this lies in what follows: Let us admit that time arises by degrees; then it would exist after it was nonexistent previously, indeed already prior to its existence. The earlier and the later are, however, two designations for parts of time. Therefore, time would have to exist before there was any. Furthermore, if time were something that originates, then it would happen that time which might be a present time did not precede a particular thing. However, it is quite impossible to imagine that no past preceded a particular thing which is in actuality and exists in a "present" moment, let alone that we could imagine such a state of affairs were we to reflect on the real nature of time. An error in these ideas can occur only when we think of time in terms of a line; for, in so far as the line possesses spatial motion -- this exists in actuality -- it is by necessity finite, not to mention the fact that one cannot even imagine infinity in connection with it. Now, if you should imagine time in this sense as a straight line, it is impossible for it to be infinite. This type of error belongs to those that fall under the topic of spatial motion and substitution. Farabi has composed long dissertations concerning this problem with respect to things that exist and change.

This being so, and it being evident that time forms an eternal continuum, it follows inevitably upon an eternal motion which is continuous and uniform; for a motion which in the proper sense of the word is uniform, is the continuous motion. If, now, there exists in the "here" an eternal motion, it follows that there must also be present an eternal mover who is ever the same; for, if there were many moving principles existing, the motion would not be one and the same, nor would it be continuous. Now, that this first mover cannot be of a material nature, has become intelligible by virtue of the fact that his motion, which takes place in time, proceeds "without end. However, every mover that exists in some matter must have quantity adhering to him, that is, must possess a body. Every potentiality, however, which has its seat in something quantitative, is divisible, corresponding to the divisibility of quantity. It follows likewise in the determination of finiteness and infinity, as has been demonstrated in natural science, be it that one presupposes this potentiality as blended with the body or only as "engraved" upon it. Of such nature are heat in fire and cold in water. This potentiality is in some sort of necessary internal dependence on the hyle, that is to say, a dependence absolutely necessary for its existence. Thus with respect to the psychic principle. Since, now, in essence, form is material, no material force can exist which, as moving principle, is infinite. All this was demonstrated in natural science...

... The Metaphysics of Averroes, ibn Rushd (Averroes)