How Aquinas confuses the First and Second way

[Linusthe2nd]

Linus my statement is, to the best of my knowledge, a direct corollary of the First two Laws of Motion. If you doubt the consistency of this statement with observed reality then
I think it is your grasp of modern Physics that is questionable. Sure, say modern Physics is wrong, but at least demonstrate that you understand what modern Physics actually says. I am not convinced you do sorry.

I am more interested in what modern Physics observes re these sorts of empirical issues Linus. If you could explain what you mean by “violent motion” then I will endeavour to analyse it and see if I agree that modern Physics is mistaken on that point.

Of course not, its now a given of observed nature.
You only question it because you hold to motion “laws” inducted from ancient (and incomplete) observations of nature that you are loathe to question.

They cannot both be right so if you don’t question one then you must question the other.

I have given solid reasons for everything I have said. You raised the questions, I answered them. Either you haven’t read what I said or you have not studied it. These are prerequisites to honest discussion. I’m not going to go over the whole thing again.I could be wrong but I don’t think so. I have read the sources and the arguments of the sources seem reasonable to me.

There is a difference between natural motion and violent motion. Violent motion is motion which flows naturally from its form. For example, if you see a cow flying through the air, you know something external to it has launched it. because it is not according to nature that it should fly. On the other hand, my heart pumps because it is part of my nature that my heart should pump. No external cause is required unless one considers the generator of my nature, God.

There is a difference between the constant motion of a space ship and a heavenly body. The former, when its fuel is exhausted, will continue at a near constant velocity due to its altered nature, something to which all bodies are susceptible. A natural heavenly body has a nature which likewise will continue at a near constant velocity. Other than natural cause which are sourced in the generators of such bodies, the only explanation is the direct causality of God or his Angels, but ultimately of God.

As far as the initial cause of such velocity, one certainly knows that, for artificial bodies, the cause is man. The initial cause of the velocity of a heavenly body is unknown but it has a cause. It could even be the direct causality of God or his Angels.

If these explanations are unpalatable to modern science, that cannot be helped.

Linus2nd .

 

[utunumsint]

I think I will redo my post on paragraph 8. I know a little bit more about what Aquinas meant by quid movetur ab alio movetur, given the principles he establishes in paragraph 5. Specifically his point 5.1 defines an essential criteria for anything to constitute a self mover: “Point 5.1 If something moves itself, it must have within itself the principle of its own motion; otherwise, it is clearly moved by another.” I think in most discussions, this criteria is ignored or overlooked.

So lest iron out the points Aquinas makes in 8,

• Point 8.1- Whatever is moved by accident is not moved by itself, since it is moved upon the motion of another.
• Point 8.2- So, too, as is evident, what is moved by violence is not moved by itself.
• Point 8.3-Nor are those beings moved by themselves that are moved by their nature as being moved from within; [The next few clauses are further examples of point 3.]
• Point 8.3.1-such is the case with animals, which evidently are moved by the soul.
• Point 8.3.2-Nor, again, is this true of those beings, such as heavy and light bodies, which are moved through nature. For such beings are moved by the generating cause and the cause removing impediments.

(cool - nested bullets work! )

Now point 8.1 covers accidental change. For example, a person moving on a train is not moving himself, but the train that he or she is on is moving, and she is therefore moving in terms of the accident of place. Clearly this is not an example of a self mover, since she is not the cause of her own motion. She is not a self mover (at least with regard to the example used… perhaps I should have used something inanimate instead for my example, instead of a human being with a soul). The train is. But lets use Newton’s example of sustained motion through empty, frictionless space. What is to be proved in Aquinas’ view is not simply that there seems to be no efficient cause for sustained motion, but that, as per principle 5.1, that the motion must be self caused motion such that an object initially at rest spontaneously begins to move, or vice versa, a moving object were to suddenly, spontaneously, move itself into a position of rest via some internal principle. Now, I personally agree with Linus that there must be a cause of sustained motion otherwise the principle of causality would be violated. I locate that causality in the nature of the object itself, and I don’t think it is an instance of efficient causality, except when viewed from the standpoint of God who creates those natures capable of such motion, and having the prerequisites (such as mass, quantum energy field which makes up the substance of all physical things, etc…) to make such motion possible. But that is neither here nor there, in the terms that Aquinas himself has established. Specifically the principle in 5. 1.

Any objections? If so, please make your objections based on the text being analyzed.

Point 8.2 also seems self evident. Any objection to this one?

Point 8.3 establishes natural inner principles of motion, such as in 8.3.1 where an animal is moved by their soul, and in 8.3.2 in the postulated motion of objects that seemed to Aquinas to be self moved, such as the planets and the spheres. He gets around that one by stating that said planed are not instances of self movers because they are generated, and so are not instances of a self mover as established in 5.1, but get their motive power by receiving their nature from another.

Now 8.3.2 is interesting because it is the most evident example of sustained motion that could be available to an ancient observer. And in fact, Newton, I believe, based at least part of his Principia on an analysis of Kepler’s observations of planetary motion. It is also interesting that Aquinas, at least in this spot, does not try to explain the sustained motion, but simply points to the general fact that such movers must have a nature that can sustain motion in this way. But based on the principles he has established in 5.2 and 5.3, he would reject such movers as true instances of a self mover as established in 5.1. The moon and the planets are clearly divisible and consisting of material parts. Only divisible and material things with parts can move in the way the planets do. Therefore something must have put them in motion, at least in terms of generation, because they could not have been the cause of their own actualization since they are composites of form and matter, essence and existence, and so on.

But these are my thoughts. Lets move on to see how Aquinas deploys these principles.

God bless,
Ut

 

[utunumsint]

For those of you catching up, here is a TOC of my analysis and Balto’s analysis of paragraphs 5 through 8 in the Summa Contra Gentiles chapter 13 in book one:God

• Ut Paragraph 5 - Mostly principles that establish what could constitute self mover that is not moved by another
• Ut Paragraph 6
• Ut Further reflections on paragraph 5 and principle 5.1
• Balto Response to Ut on paragraph 5
• Ut Paragraph 7
• Balto Response to Ut on paragraph 6
• Ut Paragraph 8 initial analysis of Aquinas’ principles

I will probably post these again with new additions every once and a while.

God bless,
Ut

 

[utunumsint]

Continuation of paragraph 8

Now, whatever is moved is moved through itself or by accident [point 8.1].

He goes on to expand on what he means by through itself in the next few sentences. It is interesting that he doesn’t seem to think point 8.1 is worth more than a brief mention since it is so self evident to him.

If it is moved through itself, then it is moved either violently [point 8.2] or by nature [point 8.3]; if by nature, then either through itself, as the animal [point 8.3.1], or not through itself, as heavy and light bodies [point 8.3.2]. Therefore, everything that is moved is moved by another.

It looks like when he says “through itself”, he means either a being with a nature that has a soul, such as a vegetative, animal, or rational soul, or without a soul, such as in heavy or light bodies. Now, if we accept his principle 5.1, then neither 8.3.1 or 8.3.2 represent instances of a self moved mover.

God bless,
Ut

 

[utunumsint]

Paragraph 9 Third proof for quid movetur ab alio movetur.

[9] In the third way, Aristotle proves the proposition as follows [VIII, 5]. The same thing cannot be at once in act and in potency with respect to the same thing.

I think this is fundamentally what he was talking about when he was discussing something at rest and in motion in the previous section. "That which is held to be moved by itself is primarily moved. [Point 5.2] Hence, when one of its parts is at rest, the whole is then at rest. For if, while one part was at rest, another part in it were moved, then the whole itself would not be primarily moved; it would be that part in it which is moved while another part is at rest. "

But everything that is moved is, as such, in potency.

Because it has parts and is divisible.

For motion is the act of something that is in potency inasmuch as it is in potency.

I think by this he means, the motion from actual point A is in potency to potential point B. The movement constitutes an actualization of a potency in A for B.

That which moves, however, is as such in act, for nothing acts except according as it is in act.

OK. So with regard to acceleration or any change of velocity including slowing down, this applies. It requires that something else make that change in motion possible. The same thing cannot be both the cause of its current motion and of its change in motion. Again, according to the principle 5.1, a self mover would have to be able to make this change occur within itself.

Therefore, with respect to the same motion, nothing is both mover and moved. Thus, nothing moves itself.

OK.

God bless,
Ut

 

[utunumsint]

Paragraph 10

[10] It is to be noted, however, that Plato, who held that every mover is moved [Phaedrus], understood the name motion in a wider sense than did Aristotle. For Aristotle understood motion strictly, according as it is the act of what exists in potency inasmuch as it is such.

Interesting. So he is going to unpack how Plato and Aristotle differed in their understanding of motion.

So understood, motion belongs only to divisible bodies, as it is proved in the Physics [VI, 4].

Aquinas has already stated this in principle 5.3 "Point 5.3 - It is also necessary that a self-moving being be divisible and have parts, since, as it is proved in the Physics [VI, 4], whatever is moved is divisible. "

According to Plato, however, that which moves itself is not a body. Plato understood by motion any given operation, so that to understand and to judge are a kind of motion. Aristotle likewise touches upon this manner of speaking in the De anima [III, 7]. Plato accordingly said that the first mover moves himself because he knows himself and wills or loves himself. In a way, this is not opposed to the reasons of Aristotle.

Right, so for Plato, operations of the mind constitute motion, whereas for Aristotle, he restrict his definition of motion to the movement of divisible bodies, although he did acknowledge Plato’s way of talking about motion.

There is no difference between reaching a first being that moves himself, as understood by Plato, and reaching a first being that is absolutely unmoved, as understood by Aristotle.

So the main difference is Aristotle’s theory of potency/actuality - his moderate realism about the forms as opposed to Plato’s idealism about the forms. I’m sure this section could be expanded a great deal.

God bless,
Ut

 

[utunumsint]

TOC of analysis for paragraphs 5 through 10 in the Summa Contra Gentiles chapter 13 in book one:God

• Ut Paragraph 5 - Mostly principles that establish what could constitute self mover that is not moved by another
• Ut Paragraph 6
• Ut Further reflections on paragraph 5 and principle 5.1
• Balto Response to Ut on paragraph 5
• Ut Paragraph 7
• Balto Response to Ut on paragraph 6
• Ut Paragraph 8 initial analysis of Aquinas’ principles
• Ut Paragraph 8 continued
• Ut Paragraph 9
• Ut Paragraph 10

God bless,
Ut

 

[Richca]

I like the logical approach Richca but I don’t think this is the solution to the conundrum.

I don’t see how Aristotle would ever say that any sort of locomotion (uniform or otherwise) could not be demonstrating change. Because for him its really about place

 

[Richca]

(Continued from previous post)

 

[balto]

Well that’s out of left field. Do go on, this may be the cause of our inability to quite see eye to eye wrt chains of cause/effect wrt local motion.

Wait, what? How is this out of left field? I have been trying to get you to understand this point for several pages of this thread already. This is the last way I can think to explain this point. The rock is changing only because the atoms at the interface of the rock and stick are repelling only because the atoms are being held together by nuclear forces only because the protons, neutrons, and electrons are attracting only because the quarks are doing what they do … only because God is making it the case that X, Y, and Z have the natures they do (i.e. He is actualizing essences, doing what Aquinas calls "conjoining an act of existence with an essence). My physics is probably wrong but the point still remains: that is instrumental causality. The effects are unfolded within time. Human sensation is also a process that occurs in time. So we need time to observe change. But our intellects are able to grasp the necessity of instrumental chains throughout the timespan of change by abstracting from this sensitive data.

 

[balto]

This statement seems to contradict the point that Aquinas makes in 5.2.1 where he explains that anything with parts would have one part in actuality that moves another part at rest, and basically actualizes it.

No, I don’t think there is a contradiction here. He is saying that some hypothetical objector might try to claim that if something is self-moved, then all of the parts would have to be changing. Aquinas is arguing that some of the parts can be at rest when a self-movement is happening. If I raise my right hand, then my left hand is not being moved, but I am still self-moving. I think Aquinas is arguing that the whole thing cannot move the whole thing (i.e. the human soul cannot move the whole human soul, but the soul can move a part of the whole, which is why a self-mover is composite). I guess God is not considered a self-mover, but that would make sense because if God were a self-mover then He would be able to change Himself.

This one also contradicts what Aquinas says in 5.2.1.

I don’t know what argument Avicenna was advancing, so I don’t know if we can comment too much on this point. But if there is a contradiction here I would think that Avicenna is contradicting Aristotle and Aquinas is defending Aristotle.

Here he seems to be insisting that a self mover cannot have parts.

Well I don’t think he can be saying that, because just a couple of sentences earlier he was arguing that a self mover has to have parts, right? When he says that “if something moves itself primarily and through itself, rather than through its parts, that it is moved cannot depend on another” I think he means that a self mover is not moved by any other natural cause. If you only saw my arm moving, you would conclude that the arm qua arm does not have the power to raise itself, so it must be moved by violence. But then you see the whole person and note that the arm is moved by the human soul, but the human soul is a self-mover, so there’s no other natural thing moving the human soul by violence. But you’re not done here, because the human soul is contingent; it may or may not exist. So God is actualizing the human soul’s essence’s potentiality for existence by “conjoining it with an act of existence” as Aquinas likes to say. So the human soul is “existentially moved” although it is not “naturally moved” whereas God is neither existentially nor naturally moved. I think that is what he has in mind, or at least that is the only way I can make sense of it .

A self mover that is at rest is an inherent contradiction, pointing to the idea that a self mover must be pure actuality, I guess.

No I don’t think that a self-mover needs to be pure actuality, only that it has “active powers” as it were. The notion of an active power is still somewhat confusing to me. It refers to a self mover being able to do something through its own nature. So I have the active power for speaking because my nature allows me to speak, even though it need not be the case that I am constantly speaking. And it could even be the case that another thing, acting on me through “violent movement”, can prevent this active power from being able to manifest, such as if I acquired some biological disease that resulted in my becoming mute. This active power “counts” as an actuality supposedly. There was a thread on this a couple of months ago where someone was asking if God can really be pure actuality if there are worlds whose essence He does not actualize (because prima facie it would seem that God has a potential to create these worlds that remains unactualized, so He would be a compound of actuality and potentiality after all). After perusing the comments on an article on Feser’s blog it seems that God has an active power for actualizing Narnia, which makes Him purely actual even though that power is unexercised.

What I find interesting about this first approach is that locomotion is never even mentioned.

Yeah, that’s what I’d like to see. Because I think that at least some of their understanding of locomotion really is predicated on faulty physics.

 

[utunumsint]

No, I don’t think there is a contradiction here. He is saying that some hypothetical objector might try to claim that if something is self-moved, then all of the parts would have to be changing. Aquinas is arguing that some of the parts can be at rest when a self-movement is happening. If I raise my right hand, then my left hand is not being moved, but I am still self-moving.

I should have worded that better. Yes, I agree with your interpretation here and I understood that he was setting up some counter examples that contradict his original claim without getting into too many details in refuting them. You would probably have to read Avicenna to find out exactly what he was claiming. Perhaps Aquinas refutes his arguments in some other place.

I think Aquinas is arguing that the whole thing cannot move the whole thing (i.e. the human soul cannot move the whole human soul, but the soul can move a part of the whole, which is why a self-mover is composite). I guess God is not considered a self-mover, but that would make sense because if God were a self-mover then He would be able to change Himself.

I don’t think I agree here. How can he be arguing this if the essense of a soul is in potentiality to existence, and participates in existence itself as potency to actual? This is the basic idea behind on being and essence right?

Well I don’t think he can be saying that, because just a couple of sentences earlier he was arguing that a self mover has to have parts, right?

I think you are referring to is this: “Point 5.3 - It is also necessary that a self-moving being be divisible and have parts, since, as it is proved in the Physics [VI, 4], whatever is moved is divisible”

But I suspect that he is setting a trap here with this point. If a self mover must have parts so that it can move, then it will have potentialities within itself that can be moved (changed).

When he says that “if something moves itself primarily and through itself, rather than through its parts, that it is moved cannot depend on another” I think he means that a self mover is not moved by any other natural cause. If you only saw my arm moving, you would conclude that the arm qua arm does not have the power to raise itself, so it must be moved by violence. But then you see the whole person and note that the arm is moved by the human soul, but the human soul is a self-mover, so there’s no other natural thing moving the human soul by violence. But you’re not done here, because the human soul is contingent; it may or may not exist. So God is actualizing the human soul’s essence’s potentiality for existence by “conjoining it with an act of existence” as Aquinas likes to say. So the human soul is “existentially moved” although it is not “naturally moved” whereas God is neither existentially nor naturally moved. I think that is what he has in mind, or at least that is the only way I can make sense of it .

LOL - I should have read on before making my last comment. Yes. I agree with you. But then, like I said, doesn’t this mean there is no such thing as a self mover?

No I don’t think that a self-mover needs to be pure actuality, only that it has “active powers” as it were. The notion of an active power is still somewhat confusing to me. It refers to a self mover being able to do something through its own nature. So I have the active power for speaking because my nature allows me to speak, even though it need not be the case that I am constantly speaking.

Yes, but such a self mover would not be truly a violation of quid movetur ab alio movetur, because of what Aquinas says in pararaph 8 forums.catholic-questions.org/showpost.php?p=12402861&postcount=162 See points 8.3, 8.3.1, and 8.3.2. I interpret this as not truly being a self mover - or perhaps I should interpret it as self movement, but not such that violates the principle in question.

And it could even be the case that another thing, acting on me through “violent movement”, can prevent this active power from being able to manifest, such as if I acquired some biological disease that resulted in my becoming mute. This active power “counts” as an actuality supposedly. There was a thread on this a couple of months ago where someone was asking if God can really be pure actuality if there are worlds whose essence He does not actualize (because prima facie it would seem that God has a potential to create these worlds that remains unactualized, so He would be a compound of actuality and potentiality after all). After perusing the comments on an article on Feser’s blog it seems that God has an active power for actualizing Narnia, which mkes Him purely actual even though that power is unexercised.

,

Interesting.

Yeah, that’s what I’d like to see. Because I think that at least some of their understanding of locomotion really is predicated on faulty physics.

Right. The principles in question here do not even touch on locomotion, as far as I can tell, which is interesting, because they show that “quid movetur ab alio movetur” does not rest on claims about locomotion.

God bless,
Ut

 

[Blue_Horizon]

The wording of Newton’s first law of motion does lend itself to some confusion. As it stands, it states that a body at rest needs an external mover to set it in motion.

Yes, I think that is validly inferred.

This is reasonable and consistent with Aquinas and sense observation. Next, it states that a body in uniform motion in a straight line, needs an external mover to change it from this state which is also reasonable if there is such a body in actual existence.

Ok with that too.

Here we have a body in motion and at one and the same time in a state which denotes stability.

OK but I am not quite sure what you mean by “stability.”
If you mean the net balance of vector forces acting on it is zero then yes I believe this statement is compatible with modern Physics. In this sense both zero velocity and const speed in a straight line are exactly the same.

This is precisely what Aquinas says is impossible in the first way argument. It is not possible for an object to be in motion and not in motion at one and the same time according to the same species of motion. It is not possible for wood to be potentially hot and actually hot at the same time.

OK this is where I don’t quite get the connection.
“Motion” (ie a changing of place) and “stability” (as defined above by modern Physics) would not be the same thing from what I can see.

Newton was a physicist and maybe physicists don’t pay much attention to their wording of things. Aquinas, though primarily a theologian, was also a philosopher and metaphysician and the proper use and meaning of words in this science can be very important especially in demonstration. Words are important …

Absolutely.

I find a lot of people don’t always pay due attention, including translators of latin or the harried scribes of Aquinas at times .
Of course some things cannot be translated 100% in a single literal translation into English. eg “movetur” in Latin is apparently of “present simple” tense/aspect. So the expression does not distinguish between ongoing application of force or a brief impulse.

However, I think we get the meaning of Newton’s first law of motion and however it is worded, it is irrelevant to the issue at hand.

I wasn’t aware there was an ambiguity….

Aquinas’ analysis of motion or change in the first argument involves a being setting something in motion and as long as a thing continues in motion it requires a mover.

Not quite sure what you mean here.
I’ll assume you mean " involves a being setting something in motion and as long as a thing continues in motion it also requires a sustaining mover."

Whether you move a stick with the hand for five seconds or five minutes it is evident that the motion of the stick depends on the motion of the hand.

Of course. What I object to is people saying that the linked locomotive chains of cause/effect involved all happen at the same time (“simultaneous”) and are not temporally sequential.

Your analysis in previous posts as dividing the motion of the stick into parts such that the top of the stick moves before the bottom of the stick which may be true in a sense is irrelevant to the issue at hand and Aquinas makes no mention of this sort of analysis in the first way argument.

I am not sure about that due to the infinite regression stuff.
Aristotle appears to say that infinite regression of the above chains of locomotive causality (or at least some forms of accidental change) is not an inherently illogical proposition. hence he sees the world as having no temporal beginning. Aquinas appears to agree with this logic even if his Faith tells him that in fact the world did have a beginning (and was necessarily created with initial locomotion by God).

As I pointed out in a previous post, the analysis of change or motion as given by Aquinas involves a mobile object or being in potency which is the subject of change and a mover or being in act. Change involves the production of being, something new.

I wouldn’t really call an accidental change (eg a change in place) “the production of being” except in a very remote analogical sense. I wash my grey cat and it becomes a white cat. That isn’t really the production of a new “being” though it certainly is change.

In the first way argument, Aquinas is not particularly concerned about tracing a series of movers such that 50 is moved by 49, and 49 is moved by 48 and so on to mover 1. One such instance of change or motion is enough to establish the argument in that it is not possible to proceed indefinitely in a series of simultaneously existing movers wherein the causality of each moved mover in such a series is dependent on the simultaneously existing prior mover. This simultaneity of the existence of each mover in such a series is the kind of series Aquinas has in mind in the first way argument and which he calls an ordered series per se. An ordered series per accidens is linear, temporal, stretches back in time and most importantly the causality of a member of this series does not depend on the simultaneous causality of a prior member. For example, though Isaac was generated from Abraham and Sarah, he begot Jacob independantly of Abraham and he could do this whether Abraham was alive or not.

This is interesting.
But we probably cannot ratchet up to the more generic metaphysical propositions if we cannot yet agree on your temporal propositions re change above I suppose.

 

[balto]

Now point 8.1 covers accidental change. For example, a person moving on a train is not moving himself, but the train that he or she is on is moving, and she is therefore moving in terms of the accident of place. Clearly this is not an example of a self mover, since she is not the cause of her own motion. She is not a self mover (at least with regard to the example used… perhaps I should have used something inanimate instead for my example, instead of a human being with a soul). The train is. But lets use Newton’s example of sustained motion through empty, frictionless space. What is to be proved in Aquinas’ view is not simply that there seems to be no efficient cause for sustained motion, but that, as per principle 5.1, that the motion must be self caused motion such that an object initially at rest spontaneously begins to move, or vice versa, a moving object were to suddenly, spontaneously, move itself into a position of rest via some internal principle. Now, I personally agree with Linus that there must be a cause of sustained motion otherwise the principle of causality would be violated. I locate that causality in the nature of the object itself, and I don’t think it is an instance of efficient causality, except when viewed from the standpoint of God who creates those natures capable of such motion, and having the prerequisites (such as mass, quantum energy field which makes up the substance of all physical things, etc…) to make such motion possible. But that is neither here nor there, in the terms that Aquinas himself has established. Specifically the principle in 5. 1.

Any objections? If so, please make your objections based on the text being analyzed.

Yes, I think you are right, especially about the part about there being a need for a cause of sustained motion. But that is just God continuously causing the essence to be actualized though right?

Point 8.2 also seems self evident. Any objection to this one?

No objections here. Although I am a little confused as to what the difference between being moved “accidentally” and being moved “violently.” They seem to be the same thing.

Point 8.3 establishes natural inner principles of motion, such as in 8.3.1 where an animal is moved by their soul, and in 8.3.2 in the postulated motion of objects that seemed to Aquinas to be self moved, such as the planets and the spheres. He gets around that one by stating that said planed are not instances of self movers because they are generated, and so are not instances of a self mover as established in 5.1, but get their motive power by receiving their nature from another.

Now 8.3.2 is interesting because it is the most evident example of sustained motion that could be available to an ancient observer. And in fact, Newton, I believe, based at least part of his Principia on an analysis of Kepler’s observations of planetary motion. It is also interesting that Aquinas, at least in this spot, does not try to explain the sustained motion, but simply points to the general fact that such movers must have a nature that can sustain motion in this way. But based on the principles he has established in 5.2 and 5.3, he would reject such movers as true instances of a self mover as established in 5.1. The moon and the planets are clearly divisible and consisting of material parts. Only divisible and material things with parts can move in the way the planets do. Therefore something must have put them in motion, at least in terms of generation, because they could not have been the cause of their own actualization since they are composites of form and matter, essence and existence, and so on.

I guess his thoughts on planetary motion are especially relevant to the current discussion about whether constant velocity objects require a sustaining cause for the velocity specifically. It is interesting that he does not think that they are self-movers even though to the medieval mind I can certainly see why it would be tempting to call them self-movers. But he is actually technically physically correct that they would require their motion from another acting agent since, although he didn’t know it at the time, the planets are constantly changing velocity because the gravitational pull of the sun causes them to constantly change their direction and orbit in an elliptical path. So we still don’t know what he thinks about an object moving at a constant velocity.

I don’t quite know what a “generating cause” and a “cause removing impediments” are though. Generating causes would seem to apply to animate as well as inanimate objects. From a modern perspective, I don’t think there is any reason to view a planet any differently than any other inanimate object.

 

[balto]

Paragraph 10

Interesting. So he is going to unpack how Plato and Aristotle differed in their understanding of motion.

Aquinas has already stated this in principle 5.3 "Point 5.3 - It is also necessary that a self-moving being be divisible and have parts, since, as it is proved in the Physics [VI, 4], whatever is moved is divisible. "

Right, so for Plato, operations of the mind constitute motion, whereas for Aristotle, he restrict his definition of motion to the movement of divisible bodies, although he did acknowledge Plato’s way of talking about motion.

So the main difference is Aristotle’s theory of potency/actuality - his moderate realism about the forms as opposed to Plato’s idealism about the forms. I’m sure this section could be expanded a great deal.

God bless,
Ut

I agree with your conclusions in the post and the couple that precede it (paragraphs 8-10).

 

[balto]

LOL - I should have read on before making my last comment. Yes. I agree with you. But then, like I said, doesn’t this mean there is no such thing as a self mover?

Yes, but such a self mover would not be truly a violation of quid movetur ab alio movetur, because of what Aquinas says in pararaph 8 forums.catholic-questions.org/showpost.php?p=12402861&postcount=162 See points 8.3, 8.3.1, and 8.3.2. I interpret this as not truly being a self mover - or perhaps I should interpret it as self movement, but not such that violates the principle in question.

Well he seems to be trying to argue that a self-mover would not violate quid movetur ab alio movetur. I suspect that he identifies self-movers with living things, so there are such things as self-movers. He tries, correctly, also to refute that planets are self-movers because they appeared to many people to be self-movers like animals. But yeah, the principle is not violated even for self-movers since, as we saw earlier, they still require an actualization of their natures/souls. Moderns like to say that living things are not really self-movers, because external factors move them violently/accidentally I suppose. I would say that rational animals are certainly self-movers but I don’t know whether lower animals are also self-movers. Even if we all were only moved violently/accidentally, we would still not get away from “quid movetur ab alio movetur”, it would just be easier to justify because then you wouldn’t have to deal with self-movers at all.

 

[utunumsint]

Yes, I think you are right, especially about the part about there being a need for a cause of sustained motion. But that is just God continuously causing the essence to be actualized though right?

Well, fundamentally, that is a source of change in everything that exists. It is a composite of essence and existence. But he could have made essences to exist that were completely incapable of motion, so I believe that he must have caused specific natures and conditions in nature where motion, such as sustained motion would be possible.

No objections here. Although I am a little confused as to what the difference between being moved “accidentally” and being moved “violently.” They seem to be the same thing.

Agreed. The 10 categories seem sufficient to explain any kind of change. Even natural change. I mean, we could spend a lot of time analyzing all this content according to the ten categories. It would open up a can of worms, but could potentially be fruitful. But perhaps we could stay focused on Aquinas, at least for the time being.

I guess his thoughts on planetary motion are especially relevant to the current discussion about whether constant velocity objects require a sustaining cause for the velocity specifically. It is interesting that he does not think that they are self-movers even though to the medieval mind I can certainly see why it would be tempting to call them self-movers. But he is actually technically physically correct that they would require their motion from another acting agent since, although he didn’t know it at the time, the planets are constantly changing velocity because the gravitational pull of the sun causes them to constantly change their direction and orbit in an elliptical path. So we still don’t know what he thinks about an object moving at a constant velocity.

Agreed.

I don’t quite know what a “generating cause” and a “cause removing impediments” are though. Generating causes would seem to apply to animate as well as inanimate objects. From a modern perspective, I don’t think there is any reason to view a planet any differently than any other inanimate object.

Agreed. It is just an example of a self mover to the medieval mind.

God bless,
Ut

 

[utunumsint]

Well he seems to be trying to argue that a self-mover would not violate quid movetur ab alio movetur. .

Feser has a sub-section in a section on the principle of causality in Scholastic Metaphysics which talks about self motion. It is interesting. I think I’ll post some of the quotes and perhaps that will help us flesh out this section.

Apparantly, for Feser, quid movetur ab alio movetur is an instance of the more fundamental principle of causality. He defines the principle here:

It is Aquinas’s dictum that “nothing can be reduced from potentiality to actuality, except by something in a state of actuality” (Summa theologiae 1.2.3). An efficient cause, whether of a thing’s existence or of some change to it, always actualizes some potency or other. The principle of causality (which is concerned with efficient causality as opposed to final, formal, or material causality) tells us that if a potency is actualized, that can only be because some already actual cause actualizes it. That is true of passive potencies, like the liability of a glass to be shattered or of salt to be dissolved. It is also true of active potencies or powers, such as a hammer’s power to shatter glass. For though an active potency or power is a kind of act or perfection relative to the substance that possesses it, it is in potency or incomplete relative to the activity that underlies it.

Perhaps when looking at the planets, what he had in mind was an active potency, that could potentially be blocked by some impediment. But in terms of generating cause, he sees that anything with a nature that is movable, must have an explanation for that motion in terms of efficient cause of that thing’s existence. Feser goes on to say:

Perhaps less obvious an application of the idea is Aquinas’s further thesis that “every composite has a cause, for things in themselves different cannot unite unless something causes them to unite” (Summa theologiae 1.3.7) But as Aquinas goes on to say, “in every composite there must be potentiality and actuality… for either one of the parts actuates another, or at least all the parts are potential to the whole.” So for a composite to exist is just for the potency of its parts to comprise the whole to be actualized. Every composite has a cause, then, insofar as only what is already actual can actualize the potency in question.

People on this thread seem to accuse Aquinas of importing in an a priori principle when talking of a generating cause, but for Aquinas, this was clearly aposteriori. The parts of a thing are clearly in potential to the whole, therefore there must be some external efficient cause that generates that unity. I suppose, according to modern science, that would be the potential in both the male sperm and the female egg to exchange genetic information, that actualizes the beginning of the life of a new human being. For sub atomic particles, it is the potential for an atom to be composed of neutrons, protons, and electrons to generate a new element or to decompose into a new element.

Embarrassingly enough for me, Feser rejects that the principle of causality can have anything to do with the other three causes, as I’ve been arguing with Blue. He has a section on Scotus with regard to self motion where he introduces this discussion on motion. Scotus rejects quid movetur ab alio movetur, although he accepts the broader principle of causality. He does this based on human will’s ability to determine itself.

Now Thomists don’t deny that there are things (such as animals) which can in a loose sense be said to move themselves. But on analysis, in their view, such “self motion” really involves the movement of one part of a thing by another. For, they argue, since a potency qua potency is merely potential rather than actual, it can’t do anything, including actualize itself. Hence something that is already actual has to be what actualizes it.

Scotus rejects this by adding in addition to efficient causes of motion, the idea of principles, or principiation. This turns out to be exactly what I’ve been arguing for in this thread. The principles flow from the things material and formal causes. And such principles can be self causing, especially with regard to human will.

Feser responds:

For the Thomist, however, this simply blurs the distinction between a thing’s proper accidents flowing from its form, and an effects being generated by an efficient cause. Motion qua the actualization of potency is an instance of the latter, but Scotus’s account concerns the former. For Aquinas, though a material thing’s substantial form is indeed the “principle” by which it moves in the way it characteristically does )such as a heavy object’s tendency to fall), the cause of its motion is whatever generated the thing and thus imparted to it its substantial form. It is this cause of the material thing, rather than the thing itself or its form, that is the “mover”.

Although he does agree that a thing’s nature defines how a thing will move, he does not see this as an instance of efficient causality.

God bless,
Ut

 

[utunumsint]

Although perhaps I am conceding too much to Blue’s argument, which seems to reduce all motion to efficient causality without due regard to the part that form and mater play in generating the effect that the efficient causality produces in the thing moved (changed/brought into actuality from a potentiality). In the case of locomotion, this would be how the formal and material cause condition the effect produced by the initial efficient cause - e.g. acceleration or deceleration and sustained motion or rest.

So the efficient cause of the change in motion must be conjoined to the generating efficient cause of the material and formal nature of the thing moved.

God bless,
Ut

 

[thinkandmull]

“If it is moved through itself, then it is moved either violently [Point 2] or by nature; if by nature, then either through itself, as the animal, or not through itself, as heavy and light bodies.”

Something that is moved violently doesn’t move itself, as Aquinas himself said. The contradiction I pointed out is there

Hey thinkandmull,

I took a close look at Balto’s post 21 and 22. I think he is right here. Let me break down paragraph 8 in SCG and let me know if this helps clarify things:

Principle to be proved - What he is refering to here is this:** “namely, that everything that is moved is moved by another…”**

Now, before getting into the proof itself, he establishes the following key points, which he will then bring into his proof.

Point 1-

Point 2-

Point 3-

The next few clauses are further examples of point 3.

• Point 3.1 -
• Point 3.2-

Given the above points, he moves on to prove the principle that that everything that is moved is moved by another,

Now, he could have started this proof better because the way he states it seems to contradict point 2, but he goes on to bring in point 2 and 3, which he has just defined, right after making this statement. He clearly thinks that given the definitions he has provided in points 1, 2, and 3, the conclusion obviously follows as such:

So he is not contradicting himself. He is using the points he has just established in his final proof. If you want to prove the proof wrong, then you have to dispute his points 1, 2, or 3.

God bless,
Ut