Commentary On Aristotle’s Metaphysics: Book XII.6.1071b3-32; The Nature Of The First Cause Aristotle begins the text by reiterating that he has shown that there are three kinds of substances. Two of those substances are natural, and the other unmovable. Of the natural substances, one has eternal motion, and the other does not. In regards to the third substance, Aristotle says that it is necessary/compulsory, that it can not be otherwise, that it be an eternal unmovable substance. The nature of this third substance is the focus of this section. Next he refers to a previous passage in which he shows that substances are the first among things which exist, and if the first among things ceases to exist, then everything under that thing will cease to exist as well. This is why he says that there must be at least one substance which is eternal. Because if there were no eternal substance, then it would follow that nothing that exists must exist, which is impossible. He then reiterates that motion must have always existed, as it is impossible that it came to be, or cease to be. In regards to the former, motion could not have just come to be, as potential motion needs something to actualize it. Potential motion, will remain potential forever, without actualization, but there can not be mere potential, for in order for a thing to be potential, it must have the ability to be actual. Since it is plain that there is motion, as things exists, among other reasons, then motion must clearly have always existed, since it is impossible for it to come to be. “[A] becoming motion would involve, as we saw, a change previous to the first, in the same way a perishing of motion would involve a change subsequent to the last: for when a thing ceases to be moved, it does not therefore at the same time cease to be movable...nor, when a thing ceases to be a mover, does it therefore at the same time cease to be motive. Again, the destructive agent will have to be destroyed when it has destroyed, and then that which has the capacity of destroying it will have to be destroyed afterwards; for being destroyed is a kind of change. PhysicsVIII.251b29-252a3” If everything which is in motion is set into motion by something else, it is clear due to a problem of regress that there must be a first mover which is eternal and sets everything into motion. It is clear from these arguments that motion is eternal. Time can be thought of in the same way. “[H]ow can there be any before and after [,of motion,] without the existence of time? How can there be any time without the existence of motion? Physics VIII.251b11-12” It is impossible for time to not be eternal, for if it could cease to be, or it came to be, then it would follow that there was a time before time, and there will be a time after time, which is plainly impossible. Time is nothing more then the measurement of the differences between past, present, and future. It is absurd for there then to be a past before the past begun, and a future, after the future ends. Since time and movement exist in the same way, Aristotle says that either they are the same thing, as time is the measurement of movement (Physics IV), or it is an attribute of movement. Only that which is circular is continuous, of which it must be movement in place. “While in a sense we call anything one if it is a quantity and continuous, in a sense we do not unless it is whole … This is why the circle is of all lines most truly one, because it is whole and complete. Metaphysics V.1016b12-17”
It is not enough for there to be something which is capable of moving things, but actually not moving them, as there will be no movement, which as stated above, there plainly is. That which potentially can do what it is capable of doing, it turns out, need not exercise that capacity. If that thing which has the capacity did not act, then motion would not be eternal. Aristotle then proceeds to critique Platoâ€™s theory of the forms, and says that nothing is gained from believing in eternal substances. This is not enough to suppose for the existence of motion, unless there is something which causes movement, and this along with another substance besides the forms (such as mathematical principles which Aristotle mentioned earlier as posited by some previous thinkers) is not enough. Things which have the capacity to do so, may not do so; as I may choose to act or not. Even if this thing with such a capacity ends up acting, this also would not be enough, as there must be eternal movement, as was shown earlier. Since movement must be eternal, it is necessary that there be a principle, whose very substance is actuality. This principle being actuality, must actually be moving, or causing motion. Without an eternal principle, there could be no eternal motion, which was shown to be necessary. Therefore, an eternal principle must exist. This principle must also be without matter, since matter exists potentially. The principle of motion, the first mover, must exist in actuality alone, that is, that it would have always existed, never potentially being actuality. If the world, which is matter, is not eternal, then it would have to have been brought into existence by something which is, as if it were not, it too would have to have been set into motion by something else. Since this regress can not continue ad infinitum, there must be something which exists solely in actuality. An eternal mover must exist. A problem is raised in that all things which are actual, have the potential to act, but all those things which are potential, do not always act. It seems then that potential must exist before any actual, as in order to be actual, a thing necessarily has potential. If this is so, then there can not be an eternal actuality. This is absurd, as then it would be possible for things to not exist, and if at one time nothing existed, then it follows that nothing could come into existence. Earlier philosophers are then swiftly dealt with: some of which said that day appears from night, or that all things are together. He deals with them quickly, as no matter how it is looked at, they result in an impossibility. There is plainly movement. It is impossible that there be movement without something actually setting it into motion, as stated earlier. Movement requires a cause, and it is absurd that there be movement without a cause. This cause must be eternal, otherwise it too would need a cause. Bronze does not just become a bust by itself, the agent/artist must set it into motion. Menstrual fluids can not set themselves into motion wither, as they need semen to act on them. So too with the earth, as it needs seeds. There can not be motion, without something to set it into motion, and this substance must be eternal (for reasons shown above).
*I really wanted to talk about counterfactual, and agency theories of causations but I already went over the limit. Changes have been marked with [brackets] Schwartz 2
(Quotes have been referenced by their Becker numbers) Aristotle and Jonathan Barnes. The Complete Works of Aristotle :The Revised Oxford Translation. Bollingen Series ; [Works.English.1984]. Vol. 71:2. Princeton, N.J.: Princeton University Press, 1984.