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Does one experience the "force" of gravity directly if one is in free fall?

Does one experience the force on one's body from the atmospheric pressure directly?

Moreover, can it be said that the meanings of the concepts that go by the name of force in the above and in your "weight of object in hand" example are the same?

Yes, but in the different form of the acceleration toward the ground. At first the motion can only be seen (neglecting air resistance), but when one hits the ground one feels it as well.

Yes, one experiences the force of atmospheric pressure directly. The only complication here is that to perceive the phenomenon there must someway to discriminate the ever present normal pressure by experiencing a different pressure. Air travel, an elevator ride in a sufficiently tall building, or diving to the bottom of a pool will suffice, or sticking the nozzle of a vacuum cleaner against your skin.

Yes, if you understand that the "meaning of a concept" is simply the set of things it refers to. From ITOE, appendices:

Meaning and Referent

Prof. B:
Someone once raised the following objection to the idea that the meaning of a concept is its referents. Take the concept "glass," meaning drinking glasses. Suppose one person has seen millions of glasses in his life, but only those of one particular type. A second person has seen only a few dozen glasses, but of a wide variety of different types. The question is: who would know more of the meaning of the concept "glass"? Even though the first man has seen many more referents of the concept "glass," it seems that the second man, who has seen fewer of the referents, knows more of the meaning.

AR:
When you ask, "Who knows better the meaning of the concept?"—the answer is: both equally, because the concept doesn't include the non-essential variations. To have the concept "glass" means you can differentiate a glass <ioe2_236> from all other objects. Therefore their knowledge is exactly the same.

Prof. B:
But the meaning isn't just the essential characteristic.

AR:
The essential characteristic and lesser characteristics also. But now if one man has observed more characteristics than another, he knows more about the referents of the concept, which doesn't mean that he understands the meaning of the concept better.

Prof. B:
The meaning of the concept is the entities which it integrates, and you know the meaning when you know which entities it integrates.

AR:
That's right.

Prof. B:
So if they both have the same standards for integration, they both know the meaning equally.

AR:
Exactly.

Prof. B:
So, the meaning is the referents; the form in which we hold our knowledge of the meaning is the essential characteristics.

AR:
That's right. But the important distinction here is understanding the meaning of a concept versus knowing more about its referents. A simpler example of the same kind would be: who knows more about the concept "man," a layman or a doctor? Well, they both understand the concept equally, but the doctor may know more about the referents of the concept "man"—namely, about his physiology. Or a psychologist will know more about the type of consciousness of the referent.

Prof. B:
So "knowing more about the meaning" is equivocal. It could mean knowing more about the objects or knowing more about what makes those objects glasses.

AR:
Exactly. About what differentiates those objects from all others.

Prof. A:
Now I'm totally confused. Because I thought the meaning is the referent.

AR:
The meaning is the referent, but your understanding of the meaning of a concept and your knowledge about the referent aren't the same thing. <ioe2_237>

Prof. A:
By "understanding the meaning of the concept" you mean understanding what a concept means?

AR:
Yes, understanding which existents it refers to in reality. So that if you can distinguish the referents from all other existents in your knowledge, you have fully understood the meaning of the concept. But then if you study various aspects of these referents, you may come to know more about them than someone else, but that is an issue irrelevant to understanding the meaning of the concept.

Prof. A:
Then would it be correct to describe the person who goes into more intensive study as learning more about—

AR:
About the referents. Not about the meaning of the concept. That's the important thing. He knows more about the units, but not about the concept.

Understanding the meaning of a concept is an epistemological issue. It is understanding to what in reality that concept refers. It's being able to distinguish the referents from all other existents. That's understanding the meaning of a concept. How much you know about the referents is something that varies from man to man. But the understanding of the concept is the same once you can distinguish the referents from all other things.

In that sense the understanding of the concept "man" was the same a hundred years ago as it is today, or is the same today for a savage and a scientist. They both understand the concept, but one knows more about the referents than does the other.

And, incidentally, the concept subsumes all the characteristics of the referents,
known or yet to be discovered. And in that sense, what we know today—if we took the total sum of knowledge about a given concept, like "man"—would still apply a hundred years from now, when, let's assume, men will know much more. But they won't know more about the concept, they will know more about the referent of the concept.

Prof. A:
So in the argument against the analytic-synthetic dichotomy, when you say that newly discovered characteristics <ioe2_238> are included in the concept's meaning, you mean they belong to the same units.

AR:
Yes. But it doesn't change the concept.

Prof. A:
Some philosophers raise this objection: how could you mean by a concept more than you know at a given time? So the answer is: well, you don't know every aspect of the referents, but you do know fully which referents you are talking about.

AR:
And you know what you do know about these referents and by what characteristic you distinguish them from other referents, which is all that concerns you in regard to concept-formation.

Prof. B:
You do know fully now what you mean.

AR:
Exactly.

Prof. A:
The concept is fully meaningful if you can isolate validly a group of referents—

AR:
From all other referents, yes.

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... You may replace the first ball by countless other objects and still get the same result for the second ball, as long as those objects can generate an impulse that is large enough. So the event of movement, collision and ensuing impulse transfer is the determining factor, not the identity of the first object, therefore it's much more sensible to call that event the cause of the movement of the second ball. Moreover, if that object lies still, nothing will happen, it doesn't cause anything in itself.

If you replace the first ball with another you will definitely lose something, the first ball's identity. Aren't actions attributes or methods of entities? Can you abstract the attribute from the entity?

The first ball might have some method, spin. It might have some property, coefficient of friction. The first ball might have minute protuberances on it's surface. Does a force have minute protuberances on it's surface? Does a force have a surface?

By striking the cue ball (probably the first ball) below it's center of gravity you can apply backspin, or "English". But English is a property of a ball, not of a disembodied force. The success of failure of you pool shot may (in a long shot, a slice, or a three ball combo) depend on the precise cranny on which the two balls strike.

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Grames, my focus is precisely on your claim "Force is caused by your own muscles and external forces are felt by your own skin, that is the fundamental referent of the concept force."

Perhaps I don't understand precisely what you mean by "fundamental referent". Would you elaborate? The point is, as your quoted text clearly points out, fully understanding the meaning of a concept is understanding which existents it refers to in reality, i.e., distinguishing the referents of force from all others.

In the case of high school Newtonian mechanics, the referents of the concept "force" are those "influences" that change momentum... The alteration of motion is ever proportional to the motive force impress'd; and is made in the direction of the right line in which that force is impress'd.

An astronaut aboard the ISS in orbit 'round the Earth is under the influence of gravitational "forces" and yet cannot (locally) distinguish this influence from a state of no influence, i.e., the astronaut perceives no external force as in your example of a fundamental referent. Nonetheless, the astronaut's momentum is changing while orbiting the Earth. It seems to me that your fundamental referents are more likely referents for the related concepts "weight" and "pressure".

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Perhaps I don't understand precisely what you mean by "fundamental referent". Would you elaborate? The point is, as your quoted text clearly points out, fully understanding the meaning of a concept is understanding which existents it refers to in reality, i.e., distinguishing the referents of force from all others.

By "fundamental referent" I mean a referent necessarily first encountered by every child while learning to control their own body and nearby objects. The referents of force are first encountered by every child personally in the form of pushing and pulling and throwing things, and being pushed and pulled and even thrown themselves. The impersonal perspective comes next when applying his own experiences to understand what happens when he sees other people pushing and pulling, and it is yet further progress to comprehend the actions of inanimate objects as also exerting forces upon each other.

Now, I just made up that phrase "fundamental referent" in the course of trying to explain myself, and it may well cause more confusion than it clears up in one respect. I do not mean to imply there is actual and physical hierarchy at play such that a "fundamental referent" causes and explains other referents. The only hierarchies are epistemological hierarchies. Even epistemological hierarchies are not absolutes, for example Ayn Rand in ITOE gave the example of a child raised in a furniture store having "furniture" available to him as a first level concept. A child raised in a spaceship would not have to traverse any hierarchy of knowledge to grasp idea that the earth is round, he could just look out the window. While a child raised in a spaceship would not have "weight" available to him as a first level concept pushing, pulling and pressure would continue to be available and Newton's First Law would be much easier to notice in operation. But I do not see a way for it to be possible for any child to avoid learning to control his own body before turning his attention to physics. Epistemologically, forces exerted and felt by one's own body are the first referents of the implicit concept of force which are encountered by everyone long before force is conceptualized.

We do in fact live in a "furniture store" of forces. Weights, pressures, pushes and pulls are all the same kind of thing, and that is true whether there is also a change in motion or not.

In Newtonian mechanics, the true principle that The alteration of motion is ever proportional to the motive force impress'd; and is made in the direction of the right line in which that force is impress'd. fails to serve as a definition because it would exclude from the concept those forces that continue to exist in the absence of momentum changes because they are balanced by counter forces. It is not even compatible with Newton's First and Third laws applied to statics. The quantification made possible for by Newton's Second Law does not make it more true than the First and Third Laws. The referents of "force" are not different in Newtonian physics and the common understanding.

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In Newtonian mechanics, the true principle that The alteration of motion is ever proportional to the motive force impress'd; and is made in the direction of the right line in which that force is impress'd. fails to serve as a definition because it would exclude from the concept those forces that continue to exist in the absence of momentum changes because they are balanced by counter forces. It is not even compatible with Newton's First and Third laws applied to statics. The quantification made possible for by Newton's Second Law does not make it more true than the First and Third Laws. The referents of "force" are not different in Newtonian physics and the common understanding.

On the contrary, an alleged referent for "force" (singular) that does not involve change in momentum is instead a referent for "forces" (plural). Now, one needs a structure for combining forces, e.g.., vector addition and thus combining changes in momentum. Bottom line, a referent for force (singular) necessarily displays observable change in momentum.

In the case of statics, the (vector) summation of forces, via Newton's 2nd, implies the vector summation of change in momentum. That is, it is illogical to accept that forces can be balanced by counter forces and not accept that changes in momentum can be balanced by counter changes in momentum.

Consider, as a metaphor, the case of a half full glass of water with a tight fitting lid. On might say there is no evaporation of the water. Yet, water is evaporating in this example. However, water is also condensing and at the same rate so there is no net evaporation.

Edited by Alfred Centauri
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On the contrary, an alleged referent for "force" (singular) that does not involve change in momentum is instead a referent for "forces" (plural).

There is only one concept of force, not two different concepts. There are various causes of force, but once present all forces operate the same way as far the laws of motion are concerned.

In statics, nothing is moving. There is no relative velocity, no momentum, and no changes in momentum. F=dp/dt is only one of the three laws Newton described, it does not encompass all forces. When dp/dt is zero there should be no forces, but this is obviously false. No process analogous to evaporation is present.

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There is only one concept of force, not two different concepts. There are various causes of force, but once present all forces operate the same way as far the laws of motion are concerned.

I agree with this but oddly, you apparently don't. See below.

In statics, nothing is moving. There is no relative velocity, no momentum, and no changes in momentum. F=dp/dt is only one of the three laws Newton described, it does not encompass all forces. When dp/dt is zero there should be no forces,

Wrong. There should be no net force. You missed the point if you think that I claim two different concepts of force. When dp/dt is zero, either there are no forces present (is that even possible?) or there are forces present that combine to cancel.

Let forces F1 and F2 be impressed on an object. The net change in momentum is dp1/dt + dp2/dt = F1 + F2 from Newton's 2nd. This is just basic superposition. Nothing new here.

If F2 = -F1 then dp2/dt = - dp1/dt so the net change in momentum is zero just as the net force is zero.

Newton's 2nd holds for each force impressed on an object as well as their superposition.

*the notation dp1/dt is to be understood to mean "the change in momentum associated with the force F1" and likewise for dp2/dt

Edited by Alfred Centauri
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There is another formula that gives a force: F=PA (pressure times area).

P1A1 + P2A2 = F1 + F2

Why is your substitution better than mine?

:) I confess I don't have the slightest idea what you mean by "substitution" here or even what your point is with this equation.

(1) In my previous post, I simply added together two instances of Newton's 2nd:

F1 = dp1/dt

F2 = dp2/dt

------------------------------

F1 + F2 = dp1/dt + dp2/dt

That's superposition. Consider the left hand side the "input" and the right side the "output". Because Newton's 2nd is linear, superposition is valid.

If Newton's 2nd was a nonlinear equation instead like F = (dp/dt)2, superposition would not be valid as can be easily checked: (dp1/dt + dp2/dt)2 <> (dp1/dt)2 + (dp2/dt)2

(2) Your equation represents only the "left hand side" of Newton's 2nd so I don't see what you're trying to show here. You're just adding up forces; there's no dynamics content in your equation.

(3) Without further context, it's not even clear if the sum in your equation is meaningful. Pressure and area are scalar quantities while force is a vector quantity. There should be distinct unit normal vectors, one for A1 and another for A2 else it should be specified that the normals and forces point in the same direction. Further, it isn't clear how A1 and A2 relate to each other. The equation only makes sense if A1 and A2 are (i) planes and (ii) part of a larger area plane area A = A1 + A2.

Edited by Alfred Centauri
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I confess I don't have the slightest idea what you mean by "substitution" here or even what your point is with this equation.dynamics content in your equation.
Substitution refers to replacing every occurrence of an F in an equation with a dp/dt, or a PA.

(2) Your equation represents only the "left hand side" of Newton's 2nd so I don't see what you're trying to show here. You're just adding up forces; there's no dynamics content in your equation.
And why should there be any dynamics content? The only justification for a should in physics is that we should model reality as accurately as we can, but there has been no problem given in our discussion. Without such a context, there is no way to specify what the proper model and applicable equations should be.

(3) Without further context, it's not even clear if the sum in your equation is meaningful. Pressure and area are scalar quantities while force is a vector quantity. There should be distinct unit normal vectors, one for A1 and another for A2 else it should be specified that the normals and forces point in the same direction. Further, it isn't clear how A1 and A2 relate to each other. The equation only makes sense if A1 and A2 are (i) planes and (ii) part of a larger area plane area A = A1 + A2.

Here is further context:

Given: A rigid near-zero thickness 1 meter by 1 meter vertical square surface of mass 1 gram is on a desk. Describe the forces acting on the square.

Vertical components:

Gravity pulls down with force Fg = ma = 1 g X 9.8m/s2 = 9.8×10-3 N

The desk pushes up with force -Fg

Horizontal components:

The front surface has a force exerted upon it due to air pressure Fp = PA = 9.8692×10-6 N/m2 X 1 m2 = 9.8692×10−6 N

The back surface has a force exerted upon it due to air pressure of -Fp

Here is a completely different problem in which momentum does not enter at all.

Given: Two long straight parallel wires run next to each other at a distance L of 1 cm. Each carries a current of 1 ampere (I1 = I2) in the same direction. What is the force exerted on the first wire by the second wire (per unit length)?

F/length = I1B2 where magnetic field strength B2 is from the second wire and given by B=μ0I2/2πL. Substituting...

F/length = μ0I1I2/2πL = 1×10-5 N/m directed toward the other wire.

We could continue with a momentum analysis of this electrical example. If the first wire were free to accelerate toward the second wire, there would a dp/dt to talk about. But in this example the force is the given, determined by the magnitudes of the currents. The (per length) force to mass ratio gives the acceleration, which then gives the change in momentum (per length). The momentum is a function of the mass of the wire, but the force is not. Force is the independent variable, momentum the dependent variable. Force is the cause here, momentum the effect.

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Grames, you've gone way afield with these examples. Let's return our focus to the essential disagreement.

You claimed "[Newton's 2nd Law] fails to serve as a definition because it would exclude from the concept those forces that continue to exist in the absence of momentum changes because they are balanced by counter forces."

I claimed that this is wrong, that Newton's 2nd Law applies to each force impressed on an object and that, just as it is valid to sum the forces impressed to arrive at a net force, it is valid to sum the (rate of) change in momentum associated with each force individually to arrive at the net (rate of) change in momentum; that Newton's 2nd holds for each force and counter force individually as well as for their sum.

I do not see how the examples you have provided in your previous two replies relate to this disagreement.

Newton's 2nd is a linear relationship between an impressed force (stimulus) and an object's rate of change of momentum (response). Due to this linearity, superposition holds. From Wikipedia:

The net response at a given place and time caused by two or more stimuli is the sum of the responses which would have been caused by each stimulus individually.

The flaw in the claim that Newton's 2nd excludes "forces that continue to exist in the absence of momentum changes" is , as I see it, the failure to recognize that "forces balanced by counter forces" implies "momentum changes balanced by counter momentum changes", i.e.,

FNET = F1 + F2 + ... = (dp/dt)1 + (dp/dt)2 + ... = (dp/dt)NET = 0

Edited by Alfred Centauri
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Grames, you've gone way afield with these examples. Let's return our focus to the essential disagreement.

You claimed "[Newton's 2nd Law] fails to serve as a definition because it would exclude from the concept those forces that continue to exist in the absence of momentum changes because they are balanced by counter forces."

I claimed that this is wrong, that Newton's 2nd Law applies to each force impressed on an object and that, just as it is valid to sum the forces impressed to arrive at a net force, it is valid to sum the (rate of) change in momentum associated with each force individually to arrive at the net (rate of) change in momentum; that Newton's 2nd holds for each force and counter force individually as well as for their sum.

I do not see how the examples you have provided in your previous two replies relate to this disagreement.

There is a quantitative relationship between a force and a resulting motion, but you actually seem to entirely equate forces with momentum changes to the point that force is a redundant concept. I hold that there exist forces that are not just a 2nd Law perspective on observed momentum changes. I find your insistence that you can find momentum changes where there is no motion to be inexplicable and non-physical.

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... but you actually seem to entirely equate forces with momentum changes to the point that force is a redundant concept.

Really? I honestly cannot understand how one could draw that conclusion. Consider the following quote from my previous post:

Newton's 2nd is a linear relationship between an impressed force (stimulus) and an object's rate of change of momentum (response).

That statement should have demolished any notion that I equate force with rate of change of momentum.

As to your worry that non-zero components of rate of change of momentum are non-physical when there is zero net rate of change, I ask you to look no further than your own pressure example.

Despite the fact that the plate upon which atmospheric pressure is impressed appears to have zero change in momentum, it (as a whole) is in fact constantly changing momentum as the various molecules collide with the molecules of the plate. On average, however, the net change in momentum is zero.

And for "action at a distance forces", e.g., electromagnetism, the transfer of momentum involved with the electromagnetic force is not a continuous process but rather a discreet process of emission and absorption of electromagnetic quanta. Opposing electromagnetic forces may result in zero net change in momentum on average but only because, on average, the momentum transfers that are physically occurring cancel en masse.

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Well then for the sake of the discussion I will claim that force is entirely redundant. So please attempt an explanation of why isn't force entirely redundant if there is always a momentum change behind the curtain?

And for "action at a distance forces", e.g., electromagnetism, the transfer of momentum involved with the electromagnetic force is not a continuous process but rather a discreet process of emission and absorption of electromagnetic quanta. Opposing electromagnetic forces may result in zero net change in momentum on average but only because, on average, the momentum transfers that are physically occurring cancel en masse.

Are these virtual photons accomplishing this momentum transfer?

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Well then for the sake of the discussion I will claim that force is entirely redundant. So please attempt an explanation...

No. You make the claim, you get the pleasure of supporting it.

Are these virtual photons accomplishing this momentum transfer?

According to and in the context of QED, yes. However, in QED, virtual particles represent terms in an approximate solution (a perturbative expansion) to the field equations, i.e., a convenient (for calculation purposes) fiction. However, there is some contact with evanescent modes in classical EM and the virtual photons of QED.

Nonetheless, QED is nothing more than an approximation to some deeper and undiscovered theory.

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No. You make the claim, you get the pleasure of supporting it.
Alright, try this out: Force is distinguished from momentum because momentum is conserved, force is not. If every force was the same as a momentum change, then either force should also be conserved or momentum should not be.

According to and in the context of QED, yes. However, in QED, virtual particles represent terms in an approximate solution (a perturbative expansion) to the field equations, i.e., a convenient (for calculation purposes) fiction. However, there is some contact with evanescent modes in classical EM and the virtual photons of QED.

Nonetheless, QED is nothing more than an approximation to some deeper and undiscovered theory.

I did not pay for that paper, but I did read around a bit. I don't know what to make of Nimtz yet. In trying to understand the physical meaning of the evanescent modes I came across this Guided modes with imaginary transverse wave number in a slab waveguide with negative permittivity and permeability. Negative permittivity and permeability make the evanescent modes propagate and the real modes attenuate. A plasma can make a medium with negative permittivity and permeability. My own background covered some semiconductor physics which uses electrons, holes and phonons. The holes and the phonons are virtual particles and yet still usefully describe more complex actions of masses of negatively charged electrons within a lattice of positively charged nuclei. From these examples, I infer the only way to have virtual particles is to have a background, an aether. Is the aether back?
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Alright, try this out: Force is distinguished from momentum because momentum is conserved, force is not. If every force was the same as a momentum change, then either force should also be conserved or momentum should not be.

I'm confused, I thought you were going to support a claim that force is entirely redundant? Anyhow, I agree with the above. Momentum is conserved and, in analogy with conservation of electric charge and the continuity equation, force can be thought of as a "current" of momentum (think I = dQ/dt). Here's an old paper that suggests teaching Newton's 3rd this way.

Is the aether back?

Dark energy?

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Your discussion doesn't make much sense to me. I'll tell you what I have so far:

I think we can at least establish that a force exists as an action, and the cause of that action is the entity which acts and exerts the force. This has to be so since causality is a corollary of identity, remember?

And I quote OPAR, page 16:

It is entities which act - and cause.

So in reality a force is an action nessecarily inseparable from the nature of a specific entity, that causes another entity to accelerate. If you don't think this is the case, you would have to say forces are something other than actions.

Now since causality is a corollary of identity the entity has to be the cause. You who argue that forces cause, aren't you arguing for floating actions, bypassing entites?

I think it's like this; observing a force is to apply a conceptual perspective. In reality you only see things move and influence each other. A force itself is just an abstracted action that in reality is an entity looked at from a certain perspective.

For example: An animal and a human looks at a person jump up and down once. They would see the same thing but the human would agree to having seen "a jump", while the animal would just have seen the person doing something. We can abstract actions, so isn't that what we're doing with the concept force? We can see things influence the movement of other things, and abstract the act of influence itself.

Therefore I conclude:

A force is an external cause of an entity's acceleration. And in reality that cause has to be another entity.

(Remember that the concept force is needed in order to define the concept mass, so you can't really argue that forces exist as momentum changes, because momentum change involves mass, which builds on force, which makes your definition circular)

Forces are influences that cause acceleration, influences are actions, actions are what entities do and do not exist by themselves, therefore in reality entities cause acceleration and not forces. However it is a useful conceptual tool to sometimes speak of forces as if they were "floating actions" when working out the machanics of a system.

You can add to this; the fact that all forces exist as pairs, and the above is still true.

Did I nail it there?

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And I quote OPAR, page 16:

So in reality a force is an action nessecarily inseparable from the nature of a specific entity, that causes another entity to accelerate. If you don't think this is the case, you would have to say forces are something other than actions.

Now since causality is a corollary of identity the entity has to be the cause. You who argue that forces cause, aren't you arguing for floating actions, bypassing entites?

This is the hazard of selective attention. If you are analyzing the balance of forces on an object, you don't include the entire earth in the free body diagram of the object when all you need is the force of gravity. Claiming that force is cause of motion in that context is not the same as claiming the force is a primary, a fundamental existing without its own cause in the wider context of the real world.

I think it's like this; observing a force is to apply a conceptual perspective. In reality you only see things move and influence each other. A force itself is just an abstracted action that in reality is an entity looked at from a certain perspective.

For example: An animal and a human looks at a person jump up and down once. They would see the same thing but the human would agree to having seen "a jump", while the animal would just have seen the person doing something. We can abstract actions, so isn't that what we're doing with the concept force? We can see things influence the movement of other things, and abstract the act of influence itself.

Forces are not abstractions. Forces are as directly available to your senses as any entity is. Actions are attributes, but that does not mean they are less physical than the entities causing and experiencing them. Forces are not objects, but that does not make them abstractions. The concept of force is an abstraction made out of the forces perceived, but in same sense that the concepts of rocks, trees and cars are abstractions made out of those objects which were perceived.

In the context of the human scale, entities cause forces. When we leave the human scale and go to the quantum scale, any theory that assigns the force of an action at a distance to a particle exchange is saying forces are entities. Whatever the bedrock constituents of matter are, the result is what we see at the human scale and that is what philosophy is concerned with. That is also the scale at which Newtonian physics is fully valid. So you can safely set aside quantum mechanical arguments until you pick up the study of that subject as long as you don't claim to know things which are outside of your experience, or beyond the scope of Newton's physics.

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(Remember that the concept force is needed in order to define the concept mass, so you can't really argue that forces exist as momentum changes, because momentum change involves mass, which builds on force, which makes your definition circular)

Well... the electromagnetic field (classically and quantumly) transports energy and momentum. Moreover, the quanta of light have no mass but do possess momentum and that momentum is subject to change by the gravitational "force". Finally, one doesn't even need the concept mass for momentum as momentum is the conserved "charge" associated with the spatial translation symmetry of nature.

Forces are influences that cause acceleration, influences are actions, actions are what entities do and do not exist by themselves, therefore in reality entities cause acceleration and not forces.

Let me add something here as a final thought to all this.

Keep in mind that the entity "electron", while called a particle, cannot, even classically, be separated from it's associated electric field (Coulomb field) that extends over all space. While some might claim that the field is an abstraction, as I mentioned above, that field transports energy and momentum and so is physical as an inseparable part of the entity "electron".

I mention this because when one speaks of (fundamental) entities acting (interacting) on (with) other entities, the notion of force doesn't seem so abstract when you consider that a "force" (interaction) field is an integral part of the entity - it's part of a fundamental entity's identity. What do fundamental entity's do? They interact. A fundamental particle that doesn't interact doesn't have an identity and thus doesn't exist. It is these interactions that are perceived macroscopically as forces (as well as radiation).

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Well... the electromagnetic field (classically and quantumly) transports energy and momentum. Moreover, the quanta of light have no mass but do possess momentum and that momentum is subject to change by the gravitational "force". Finally, one doesn't even need the concept mass for momentum as momentum is the conserved "charge" associated with the spatial translation symmetry of nature.
While accurate, no person could actually comprehend "conservation" or "charge" without first discovering mass.

Considering the fields as real extensions of the particles that exist is as plausible as virtual particles, and is my preferred interpretation.

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