Aristotle’s view of the universe as eternal—as everlastingly undergoing change—leads him to question the cause of everlasting change. He attributes all the changes constantly occurring on earth to the motion of the heavenly bodies. But what keeps them everlastingly in motion?
It cannot be something that is itself in motion or changing in any way. If it were, it, too, would need a cause of its motion, a cause of its changing. Given infinite time, one might go back from effect to cause in an infinite series and never reach a first cause—a mover in motion that is not itself moved by something else in motion.
A prime mover that moves everything that is in motion without moving and without being moved must
cause motion by being attractive rather than propulsive. The bat that hits the ball and propels it is the efficient or active cause of the ball’s motion. The candy in the window that entices me into the store to buy and eat it causes my motion in a different way. Without itself moving, it attracts me. It is not the
efficient but the final cause of my entering the store—the reason why I move in that direction.
To move everything else without itself being moved or in motion, the prime mover, Aristotle argues, must function as an attractive or final cause. In thinking this, he did not have in mind the gravitational attraction that the earth exerts upon the bodies that fall to its surface, or the gravitational attraction that the moon exerts upon the tides.
In his view, attractive or final causes operate on intelligences that can respond to them and adopt them as motives for action. When he says that a heavy body that falls to earth wishes to come to rest there, he is speaking metaphorically, not literally. That motion is only like the motion of the person that is attracted by the candy in the window to enter the store.
Thinking in this way, Aristotle found it necessary to endow the heavenly bodies with intelligences that function as their motors. As the engine of an automobile is its motor, so an intelligence is the motor that keeps a star in motion. But unlike the automobile engine, which must itself be set in motion, the celestial
intelligences function as motors through being attracted by the prime mover of the universe.
To be an unmoved and eternal mover of a universe everlastingly in motion, the prime mover must be
immutable. But to be immutable, in Aristotle’s view, it must also be immaterial. Anything that is material has potentialities: it is subject to change or motion. It is also imperfect, for at any time it is not actually all that it can be.
We have seen, in earlier chapters, that that which is purely or completely potential cannot exist. Nothing exists that is not actual in some respects, while being potential in other respects. The reverse, however, is not true. Pure actuality (form without matter) can exist, though pure potentiality (matter without form) cannot.
It is by such reasoning that Aristotle came to the conclusion that the prime mover is pure actuality—a being totally devoid of matter or potentiality. In addition, this immaterial being is a perfect being, a being lacking no perfection that remains for it to attain. This perfect being, which is the prime mover of the universe, Aristotle called God.
God, for Aristotle, is not the only immaterial being in the universe. The intelligences that keep the stars in their eternal rounds through being attracted by the perfection of God are also immaterial. But though they, too, are immaterial in Aristotle’s theory, he did not regard them as perfect or pure actualities. Only
God is that.
It is difficult if not impossible to explain the potentiality that must be attributed to the stellar intelligences if they are not pure actualities. Something that is both immaterial and has potentiality does not fit easily into Aristotle’s scheme of things.
To modern ears, Aristotle’s account of what keeps the universe everlastingly in motion sounds
mythical. Yet it is interesting to follow the reasoning that led him to affirm the existence of the immaterial and perfect being that he called God. That reasoning provided a model for later thinkers in their efforts to prove the existence of Good—not Aristotle’s God, but the God of Genesis, the God who created the world out of nothing.
The conception of God as Prime mover and the conception of God as Creator are alike in three
respects: the immateriality, the immutability, and the perfection of the Divine Being. But Aristotle’s Prime Mover only serves to account for the eternity of the universe and its everlasting motion. It was the need to explain that which led Aristotle to develop his theory of the motion of the heavenly bodies and his concept of the Prime Mover as the final cause of their movements.
Aristotle did not think it necessary to explain the existence of the universe. Being eternal, it never came into existence, and so, in his view, it did not need an efficient cause that brought it into being—a cause that operated like a human maker who produces a work of art. We ordinarily speak of the human being who makes something as creative. However, the human creator always has the materials of
nature to work on. He does not make something out of nothing. He is, therefore, not creative in the way that God is thought to be creative.
The conception of God as Creator arose from the need to explain the existence of the universe, as
the conception of God as Prime Mover arose in Aristotle’s mind from the need to explain the eternity of the universe and its everlasting motion. It is difficult to determine whether the conception of God as Creator would have arisen in the minds of later thinkers in the West had it not been for the opening sentence of Genesis, which reads, “In the beginning God created the heavens and the earth.” This is regarded as divinely revealed truth by the three major religions of the West—Judaism, Christianity, and
It would be both natural and reasonable to ask whether Aristotle would have accepted or rejected
what is asserted by that sentence. Since he thought the universe to be eternal, would he not have denied that the universe had a beginning? And, denying that, would he not also have rejected the notion of a God who created it?
If to create is to cause something that does not exist to come into existence (comparable to what the human artist does in producing a work of art), then a world that has no beginning does not need a creator. But even a world that has no beginning may need a cause for its continued existence if its existence is not necessary. Something that does not necessarily exist, in Aristotle’s view, is something
that may or may not exist. If the world does not exist necessarily, it may cease to exist. What, then, keeps a world that may cease to exist everlastingly in existence?
Aristotle did not himself raise or face that question. If he had, he might have reasoned his way to the conclusion that a cause was needed to keep the universe everlastingly in existence, just as he did reason his way to the conclusion that a cause was needed to keep the universe everlastingly in motion. By a slight shift in the meaning of the word “creator,” the conclusion so reached might have led to the
conception of God as Creator, not just as Prime Mover.
In one sense of the word, to create is to cause something that does not exist to come into existence. In another sense of the word (a more subtle sense, perhaps), to create is to cause the existence of that which may or may not exist, without regard to its coming into existence. It is in the latter, more subtle sense of the word that Aristotle might have conceived God both as Prime Mover and as Creator.
The Aristotelian theories described in this chapter and the theory that I have suggested he might have developed within the framework of his philosophy are not common sense. They are not even refinements of common sense, though they may be based on such refinements.
In this very important respect, the theories dealt with in this chapter differ from the philosophical views we have considered in earlier chapters of this book. The theories dealt with in this chapter might be regarded a Aristotle’s theology, not his philosophy. If his theology is not related to our common-sense thought, as his philosophy is, it is at least related to common religious beliefs—religious beliefs that have prevailed in Western civilization for more than two thousand years. This fact is my reason for thinking that Aristotle’s conception of God, and the reasoning that led him to develop it, should be included in this book.