Aristotle – The Immovable Mover

excerpt from The School of Athens by Raphael

Some discussions never end

Plato and Aristotle held strikingly different world views. Plato believed in the existence of things unseen. He taught about Forms. Forms are the archetype for things in this world.
Forms are not part of our world. They are models for ideas and objects in our world. Are they mental? Are they spiritual? Unknown. Forms are difficult to see clearly when we live in this world. For example, consider the concept of justice. We have a general idea of justice. Justice has to do with treating people fairly. But how can we apply that principle to specific situations?
This is what I’m saying. We all understand the concept of justice. What, precisely, does “justice” mean? Define it. One person might say, “Justice is treating everyone the same.” But people are not the same. Some people are kind. Others are cruel. There are murderers and saints. Why should we treat them the same?
Another person speaks, “Justice is protecting the poor from the powerful.” OK. What if a poor person hurts a powerful person on purpose? What then? You see, we all know the idea of justice. But how do we define it? How can we ever apply it to daily life? Plato’s theory of forms was his attempt to find a solution to this question. His solution was other worldly.
Aristotle came along. He was one of Plato’s students. Aristotle ditched Plato’s theory of forms. His world view began with the physical world. Knowledge comes by examining the physical world. His approach could be called “scientific.”
How would Aristotle approach the concept of justice? By examining people. First, ask the question, “How can people best live?” Study people. Take notes. Draw conclusions. But Aristotle’s final product is as confusing as Plato’s. Aristotle’s method is totally different from Plato’s. But they come to the same conclusion. The concept of justice is impossible to define.

Aristotle from Greece

Aristotle the philosopher

Plato, Aristotle, and God

The first Ancient Greek philosophers had some ideas in common. They were fascinated by the idea of change. How does change take place? Is change possible apart from motion? Some of them saw change as a universal constant. Is there a principle in change that goes beyond the physical world? How is change related to God?
Greeks also thought of matter as eternal. Matter (substance) can change its appearance. The basic substances are eternal. They also considered time as eternal.
This is their problem: What (or Who) caused the first change? We saw how Plato handled that problem. He said there must be a first motion. This would cause the first change. First motion is a logical necessity. In other words, first motion must exist. It cannot not exist.
But, for Plato, motion comes from a living source. Look around. This seems to be true. So there must be an original living source. Plato defined this as a “world soul.” In this he went beyond logic. Logic can identify the necessity for first motion. But logic can only define a few of the qualities of first motion For example, first motion must be large enough to cause the first movement. But motion does not require a living source.
Plato took his idea too far. He said motion comes from a living source. Planets always are in motion. Planets must be alive. They must have a living soul. In this, Plato moved from logic to imagination. His theory did not stand the test of time.
Along comes Aristotle. His argument for God is called the Cosmological Argument. Plato may have developed it first. Aristotle argued it best. Thus, Aristotle gets the credit for the classic form of this argument.
Aristotle sees things in terms that comprehend everything. For example, everything is either contingent or necessary. Necessary things can self-exist. God is the foremost example of a necessary being. He relies only on Himself for existence. Man is contingent. We rely on many things for existence, such as air, water, the spark of life. Aristotle has other all-inclusive categories. He sees everything as either movable or immovable. Everything, for him, is either uncaused or caused. Everything has its logical place.
Aristotle is not easy to understand. Hold on. Let’s give it a try.

Substance, Change, and Motion

Are we studying the physical world? Then were are studying substances—that is, physical stuff. How was all this stuff formed? What laws govern its nature? Aristotle wrote:

The subject of our inquiry is substance; for the principles and the causes we are seeking are those of substances. For if the universe is of the nature of a whole, substance is its first part; and if it coheres merely by . . . serial succession. From Metaphysics, Book XII, Part 1

Science is the study of the physical world. The basic form of substance is eternal. But substances go through countless changes. These changes are in a series, that is, serial succession. Aristotle continues:

There are three kinds of substance—one that is sensible, of which one subdivision is eternal and another is perishable; . . . and another that is immovable . . . The former two kinds of substance are the subject of physics (for they imply movement); but the third kind belongs to another science, if there is no principle common to it and to the other kinds. Metaphysics, XII, 1

Basically, there is sensible substance and immovable substance. Some sensible substance is eternal. The rest is perishable. What’s the difference? The eternal part of sensible substance is the basic form. For Aristotle, this included fire, water, air, and earth. We give this role to atoms (but we know atoms are not eternal). Eternal substances go through countless combinations. Perishable substances are the result.
Movement and change are the process. Movement and change are essentials for life. According to Aristotle:

For everything that changes is something and is changed by something and into something. . . . The process, then, will go on to infinity, – Metaphysics, XII, 3

Movement and, thus, change require motion. What is the source of movement, that is, of motion?

Sources of Motion

All motion is caused. Motion cannot happen on its own. For example, a rock cannot move itself. Something else must move it.
But what about living things? How can living things move themselves? They seem to have the ability to start and stop motion. How can this logically be? Aristotle resolves, “It is impossible to say that their motion is derived from themselves: this [motion] is a characteristic of life and peculiar to living things.” (Physics VIII, 4)
However, modern science is solving this mystery. We now know living bodies are never truly at rest. Hearts pump blood. Sap rises in plants. Cells are constantly replaced – both in plants and in animals. Aristotle did not have this knowledge. He used logic to fill in the gaps.
Thus all motion is caused. Motion does not begin on its own. Also “that which causes motion is separate from that which suffers motion.” All motion must be connected. All motion is caused by previous motion. And the cause of first motion is a separate entity.

A line of dominoes

One domino starts the
whole chain falling


It’s like a line of dominoes. On television a couple of years ago I saw a world record being made. It was for knocking over dominoes. Some guy put together a long string of dominoes. I can’t remember how many dominoes. Maybe there were a million dominoes. When the first domino was pushed over it started a chain of events. One domino knocked over the next. The second domino hit the third; the third hit the fourth and so on. It took fifteen to twenty minutes for all of those dominoes to fall over.
But how did that chain reaction start? A million dominoes were knocked over. They formed patterns as they fell. It was amazing! But how did it start? It started with one domino. The dominoes did not knock themselves over. One domino started it all. But that one domino had to exist. That first domino had to fall before the reaction could start.
But another truth was evident that day. How did that first domino fall? The guy who set up the chain knocked it over. In other words that first domino was acted upon by an outside source. The source was separate from the line of dominoes.
Aristotle says it’s like that for motion. We see all over the world that one motion affects a second, then a third, then a fourth. But it all starts with the first motion. There must be a starting point. And there must be a separate source that can move itself and start the first motion. Otherwise we have an infinite series. Aristotle writes that an infinite series is impossible. There must be a beginning.

Now we say that the thing is moved by . . . the first mover in the series . . . and the first mover is moved but not by anything else, it must be moved by itself.
. . . there must be something that imparts motion not with something else but with itself, or else there will be an infinite series. Physics, VIII, 5


The Eternal, Unmovable Substance

Let’s review. The world constantly changes. Change is impossible without motion. Atoms come together. They cause all sorts of things. This cannot happen without motion. Aristotle says, “the nonexistence of motion is an impossibility.”
A substance cannot move itself. Motion begins apart from physical substance. This applies both to eternal and perishable substances. One thing moves another and another and another. Therefore, according to Aristotle (and our line of dominoes):

Since there were three kinds of substance, two of them physical and one unmovable, regarding the latter we must assert that it is necessary that there should be an eternal unmovable substance. . . . it is impossible that movement should either have come into being or cease to be . . . Movement also is continuous. . . how will there be movement, if there is no actually existing cause? Metaphysics, XII, 6

Substance is eternal. Therefore, the first motion also is eternal. Again, Aristotle wrote,

here it is sufficient to assume only one mover, the first of unmoved things, which being eternal will be the principle of motion to everything else. Physics, VIII, 6

Something started motion. Aristotle proves this idea is truth. Its existence is inescapable, built upon the bricks and mortar of logic.

Did Aristotle Prove God Exists?

Aristotle proved the necessity of an eternal entity. This entity started motion. Motion expanded and multiplied. But this entity started it all.
This entity is eternal. Why? Because it lives in eternity. In addition, if the entity was not eternal, the regression of cause would resume. Regress would continue until it reached an eternal starting point. Why? Because infinite regress is not possible in space and time. An eternal entity is required by logic to get everything started in space and time.
Aristotle proved the requirement for this entity. Who is this entity? In the words of Thomas Aquinas, “Therefore it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God.”

Quotations taken from Metaphysics, Book XII by Aristotle, translated by W. D. Ross, and available at the Internet Classics Archive at

And from Physics, Book VIII by Aristotle, translated by R. P. Hardie and R. K. Gaye, and available at the Internet Classics Archive at

1 Comment

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