St. Thomas' Motion Argument and Modern Physics

[raikou]

One way St. Thomas proved the existence of God is through the argument of motion, as follows:

The first and more manifest way is the argument from motion. It is certain, and evident to our senses, that in the world some things are in motion. Now whatever is in motion is put in motion by another, for nothing can be in motion except it is in potentiality to that towards which it is in motion; whereas a thing moves inasmuch as it is in act. For motion is nothing else than the reduction of something from potentiality to actuality. But nothing can be reduced from potentiality to actuality, except by something in a state of actuality. Thus that which is actually hot, as fire, makes wood, which is potentially hot, to be actually hot, and thereby moves and changes it. Now it is not possible that the same thing should be at once in actuality and potentiality in the same respect, but only in different respects. For what is actually hot cannot simultaneously be potentially hot; but it is simultaneously potentially cold. It is therefore impossible that in the same respect and in the same way a thing should be both mover and moved, i.e. that it should move itself. Therefore, whatever is in motion must be put in motion by another. If that by which it is put in motion be itself put in motion, then this also must needs be put in motion by another, and that by another again. But this cannot go on to infinity, because then there would be no first mover, and, consequently, no other mover; seeing that subsequent movers move only inasmuch as they are put in motion by the first mover; as the staff moves only because it is put in motion by the hand. Therefore it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God.

Now, I understand that St. Thomas’ concept of “motion” is different from how this term is used in modern physics, although something tells me hey are related. My question is: how does St. Thomas concept of “motion” fit in the modern physical framework of motion?

I think it is necessary to clarify what motion, potentiality, and actuality means within St. Thomas’ framework independent from how they used in modern physics. How are they different, and how are they related? Is St Thomas’ concept of motion also applicable to modern physics?

 

[raikou]

Let me attempt at one aspect, then please correct me if I got it wrong.

Newton’s first law of motion seems consistent with Aquinas’ concept: a body tends to stay at rest or to move at constant speed unless acted upon by an outside force.

Let’s apply it in the case of a person playing billiards.

A billiard ball will remain at rest, unless a moving white billiard ball moves it. This billiard ball has a “potential” to move, but this potential can only be “actualized” by the white billiard ball acting on it. In this case, the white billiard ball is in motion which enables it to cause the other biliard ball to be in motion as well.

Now, the white billiard ball couldn’t have moved, had it not been moved by the billiard stick which in its turn, also in motion.

The billiard stick couldn’t have moved, unless moved by the moving player’s hand.

The player’s hand couldn’t have moved, unless moved by the moving arm muscles.

The arm muscles couldn’t have moved, unless moved by chemical events in the neuron-muscle junction. Now this part is trickier because I don’t know if Newton’s first law applies to chemical events…

The chemical events wouldn’t have moved, unless moved by the moving neuronal impulses coming from the brain.

The neuronal impulses wouldn’t have moved, unless moved by the brain.

The brain couldn’t have moved (to move the impulses), unless moved by the human soul. This is also tricky. Was the brain moved by unintelligible material forces, hence denying free will? Or moved by the free human soul? Also, the first law probably don’t apply here anymore because the mover is now non-material/immaterial/spiritual.

The human soul couldn’t have moved, unless moved by God - who is perpetually in “motion” without being moved by another.

Am I correct in the application?

 

[Fomalhaut]

You definitely can’t apply the first Law of motion to chemical events, but you can perfectly use the causality principle: any effect must have a cause. The part with a soul is tricky too, if you want to prove God through your reasoning, you can’t assume the existence of the soul. The brain is powered by electro-chemical reaction responding to exterior stimuli.

 

[belorg]

Let me attempt at one aspect, then please correct me if I got it wrong.

The human soul couldn’t have moved, unless moved by God - **who is perpetually in “motion” **without being moved by another.

Am I correct in the application?

No, this is not correct. What you have here is a prime mover that is in motion, but Aristotle’s and Aquinas’ Prime Mover is not in motion.
But I agree, starting the chain of moving objects with a non-moving one is nonsense. It’s like saying that the white billiard ball stays exactly where it is , but still makes the red ball move.

 

[Paddy_Walker]

maybe the prime mover is movement; not in motion, but motion.
the idea of a prime mover for all potential is a good one. if infinity is seem as a closed chain of events, or a closed loop, a circle, then that picture of infinity is impossible. motion to infinity without ever a starting point or prime mover.

 

[empther]

By motion, Aquinas didn’t just mean the motion of a billiard ball or arrow.

He was talking about all change, every kind of change, every activity, trees growing from acorns, men’s hair turning white, ice melting, leaves turning red, volcanoes spewing lava, tides coming in and out …etc etc etc etc etc etc etc.
Every kind of change, everything that requires time, everything that is brought about by something else.

 

[DrTaffy]

You definitely can’t apply the first Law of motion to chemical events

I don’t want to be a pedantic arse, but you kinda can. My PhD in Physical Chemistry involved a lot of looking at collisional physics - how a chemical reaction can be seen as two (or more, in principle) atoms coming together. You do really need more than Newtonian physics to do really interesting stuff, but if you are interested in this field I encourage you to Google and/or read up on collision theory and collisional chemistry.

That being said, as the OP pointed out, ‘motion’ for Aquinas surely means ‘the movement from actuality to potentiality’ - closer to what we would mean by ‘cause and effect’ than ‘motion’ as such. Newton’s physics actually state that a moving thing requires ‘action’ (or ‘force’) to stop it moving, not to carry on moving.

This is also an argument based on an empirical observation (“all effects are caused”) so is not an absolute ‘proof’. Worse the empirical observation is severely cast into doubt by modern theoretical physics and experimental observation (of, for example the Casimir effect) so is, in principle, void.

 

[Al_Moritz]

No, this is not correct. What you have here is a prime mover that is in motion, but Aristotle’s and Aquinas’ Prime Mover is not in motion.
But I agree, starting the chain of moving objects with a non-moving one is nonsense. It’s like saying that the white billiard ball stays exactly where it is , but still makes the red ball move.

It is nonsense only if you assume that Aquinas means motion in the everyday sense – he means change, as Empther pointed out. But his ideas on this are intrinsically linked to the concepts of act and potency. I would suggest reading Feser’s Aquinas:

amazon.com/Aquinas-Beginners-Guide-Edward-Feser/dp/1851686908

 

[empther]

Belorg ( will he never leave? ) wrote:

But I agree, starting the chain of moving objects with a non-moving one is nonsense. It’s like saying that the white billiard ball stays exactly where it is , but still makes the red ball move.

This is the usual A-team deception. :hey_bud: :slapfight: :takethat:

In physics, a non-moving object does not cause another object to start moving,
buy when we’re talking about God, the universe, and existence itself,
we’re not conducting a physics symposium.

 

[belorg]

It is nonsense only if you assume that Aquinas means motion in the everyday sense – he means change, as Empther pointed out. But his ideas on this are intrinsically linked to the concepts of act and potency. I would suggest reading Feser’s Aquinas:

amazon.com/Aquinas-Beginners-Guide-Edward-Feser/dp/1851686908

I know he means change and that makes matters worse of course.
The billiard balls are just an analogy, but it serves well to show the absolute incoherence of a Thomistic cosmology.

 

[belorg]

Belorg ( will he never leave? ) wrote:

This is the usual A-team deception. :hey_bud: :slapfight: :takethat:

In physics, a non-moving object does not cause another object to start moving,
buy when we’re talking about God, the universe, and existence itself,
we’re not conducting a physics symposium.

Yes, I know that you are special pleading and I do not really mind, but that does not mean you can just throw logic out of the window.

And if I were to leave, empther, who would you address you childish replies too? Maybe another member of the A-team?

 

[belorg]

maybe the prime mover is movement; not in motion, but motion.
the idea of a prime mover for all potential is a good one. if infinity is seem as a closed chain of events, or a closed loop, a circle, then that picture of infinity is impossible. motion to infinity without ever a starting point or prime mover.

If the prime mover is movement, then he is not the prime mover the Aquinas was talking about. But I agree: your idea makes much more sense.

 

[Paddy_Walker]

If the prime mover is movement, then he is not the prime mover the Aquinas was talking about. But I agree: your idea makes much more sense.

why is he not the mover aquinas was talking about? the concept of movement needs a source, its maybe one aspect of him.

 

[raikou]

I agree that I have misunderstood Aquinas’ concept of motion.

you can’t assume the existence of the soul. The brain is powered by electro-chemical reaction responding to exterior stimuli.

The way I see it, the soul seems to be demonstable from everyday experiences. To deny the soul is to deny free will, so that every human action only seems to cycle into this pathway:

Material world —> sensory arm of nervous system ----> chemical changes in brain —> motor arm of nervous system ----> action on the material world

The fact that we can initiate movements without necessary influence or action from the material world suggests the existence of a soul.

But I agree, starting the chain of moving objects with a non-moving one is nonsense. It’s like saying that the white billiard ball stays exactly where it is , but still makes the red ball move.

Therefore, St Thomas must have had another idea of motion (not confined to physically caused motion). He must have supposed a physical motion effected by non-physical beings (the soul for example).

But this “motion” without a physical cause appears to be demonstrable from everyday experiences, such as I demonstrated in arguing for the existence of the soul. The soul initiates free action on the brain, then to the motor system, to the environment. Your analogy sounds absurd because unintelligent matter (billiard ball) cannot initiate such motion. But the human soul can.

 

[raikou]

By motion, Aquinas didn’t just mean the motion of a billiard ball or arrow.

He was talking about all change, every kind of change, every activity, trees growing from acorns, men’s hair turning white, ice melting, leaves turning red, volcanoes spewing lava, tides coming in and out …etc etc etc etc etc etc etc.
Every kind of change, everything that requires time, everything that is brought about by something else.

Yes, I have to correct my reasoning then. While St Aquinas concept of motion necessarily includes modern physical motion, it is not confined to it.

I have to correct my statement:

The human soul couldn’t have moved, unless moved by God - who is perpetually in “motion” without being moved by another.

God is not in motion (in the sense that he is undergoing changes from potentiality to actuality), but he is perpetually in action/actuality. He is an Unmoved Mover /Unchanged Changer.

 

[raikou]

But this “motion” without a physical cause appears to be demonstrable from everyday experiences, such as I demonstrated in arguing for the existence of the soul. The soul initiates free action on the brain, then to the motor system, to the environment. Your analogy sounds absurd because unintelligent matter (billiard ball) cannot initiate such motion. But the human soul can.

Let me add that the soul is non-material. What is absurd for material things may not be absurd for non-material things.

Although the human soul is itself “changed” or “moved” by another, it is not necessary for ALL spiritual beings to be “changed” or “moved” themselves in order to effect a change on other beings.

 

[Linusthe2nd]

I know he means change and that makes matters worse of course.
The billiard balls are just an analogy, but it serves well to show the absolute incoherence of a Thomistic cosmology.

Only if you don’t want him to exist in the first place. He is a definite treat to the " Self Movers. " Isn’t that the same as " Flat Earthers. "

 

[empther]

Belorg’s post 11

Yes, I know that you are special pleading and I do not really mind, but that does not mean you can just throw logic out of the window.

In your logic, physics explains itself and everything that exists, but you don’t explain how anything can exist in the first place.

In my logic, God explains physics and everything else.

Your A-team over-simplifications are childish and fool nobody around here.

 

[belorg]

why is he not the mover aquinas was talking about? the concept of movement needs a source, its maybe one aspect of him.

If movement is an aspect of Him, then He is not immutable.

 

[belorg]

Only if you don’t want him to exist in the first place. He is a definite treat to the " Self Movers. " Isn’t that the same as " Flat Earthers. "

Who says I don’t want him to exist? I am merely looking for a logically coherent cosmology. If that were to entail a Prime Mover, then so be it.