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Newton (somewhat famously) wrote:

And this is one reason why I desired you would not ascribe {innate} gravity to me.

That gravity should be innate inherent & {essential} to matter so that one body may act upon another at a distance through a vacuum without the mediation of any thing else by & through which their action or force {may} be conveyed from one to another...

... is to me so great an absurdity that I believe no man who has in philosophical matters any competent faculty of thinking can ever fall into it.

Gravity must be caused by an agent {acting} consta{ntl}y according to certain laws,...

... but whether this agent be material or immaterial is a question I have left to the consideration of my readers.

Well we know how that went, "leaving it to the readers"... for hundreds of years we have had mass belief in "fundamental forces" as plausible.

Good old "autonomy of thougt and decision".

Recently we have replaced fundamental "forces"... with "fields". Magnetic "field", gravitational "field", electrical "field".

We have "action at a distance" across a "field" now. Or "bent 4-dimensional space-time".

So I do wonder whether Newton would be satisfied, philosophically... with our current beliefs and theories and suggestions (and what some might call conclusion)... but... that would be speculative. Impossible to verify.

I do ask:

Since Newton in his Letter to Bentley, have any other philosophers of note commented or made suggestions or assessments of the plausability of "forces" or "fields" or any "action at a distance across a void"? One of our "sort of accepted" fundamentals?

What have other philosophers said?

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They mostly hated this idea.

Gottfried Wilhelm Leibniz, who was a contemporary of Newton, criticized the notion of action at a distance. He argued for a relational theory of space and time, believing that all forces must be transmitted through a medium or by contact action. Leibniz outright rejected the idea of instantaneous action across a void.

Then Immanuel Kant acknowledged the problem of action at a distance in his work "Metaphysical Foundations of Natural Science." While he didn't outright reject it, Kant suggested that the concept of absolute space and time, as proposed by Newton, was problematic. He hinted that forces might be the result of an underlying metaphysical reality.

Ernst Mach was also critical of the concept of absolute space and time, as well as the idea of action at a distance. He proposed a relational theory of space and time, where all physical phenomena are determined by the relative motions and interactions of bodies. Henri Poincare shared similar skepticism. He said that the concept of a forse field was just a convenient mathematical abstraction and might not represent a real physical entity.

Then we have Albert Einstein, whose theory of general relativity eliminated the concept of action at a distance by describing gravity as a manifestation of the curvature of spacetime. In this framework, objects follow the geodesics (shortest paths) in a curved spacetime, rather than being acted upon by a force across a distanse. Bertrand Russell was also critical of the notion of action at a distance and the concept of absolute space and time.

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    “Leibniz outright rejected the idea of instantaneous action across a void.” — and he would be right because gravitational action is not instantaneous. It propagates at the speed of light (hence gravitational waves). Mar 7 at 20:46
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    And then there's the nonlocality principle from quantum mechanics which requires instantaneous action at a distance.
    – causative
    Mar 7 at 23:37
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There is indeed a problem with action at a distance: it has to be instantaneous, breaking the causality -- and that's the absurd part about it. And, as it happens, gravity (or magnetism, etc) is not an action at a distance -- rather, it propagates at the speed of light. At this point, we are talking about particle exchange, or disturbances in the curvature of space, on in the field -- the things that mediate the action. And, by the way, Leibniz also suggested that this has to be the case:

"It is permissible to recognize magnetic, elastic, and other sorts of forces, but only insofar as we understand that they are not primitive or incapable of being explained..." (Against Barbaric Physics, as quoted in SEP)

I'm sure that Newton would also be satisfied.

Speaking of which -- I wonder why SEP article suggested that Leibniz's polemic piece was an attack on Newton? It appears they both shared the same concern.

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    Gravitational forces are still a mystery to theoretical physics. After discovering quarks (the smallest subatomic particle) 60 years ago, scientists were not able to look any deeper into the matter. For many, it means we've reached the maximum resolution of our computer simulator (the Matrix). And the night sky we see, together with action at a distance, could be just a background in our World-PlayStation. Mar 7 at 22:44
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The way you've worded your question is a bit ambiguous, so forgive me if my reading-between-the-lines is reading incorrectly, but it seems like you're saying that modern Quantum Field Theory might be unsatisfying to someone like Newton, because you think QFT requires instantaneous action at a distance - ie non-locality - and you have other unspecified problems with the idea of fields.

I think the nature of your question might change if you found out that it's NOT a given, at all, that QFT involves non-local causality, and in fact many physicists believe simultaneously in QM, QFT and local-only causality.

If it's true that Newton would be unsatisfied with any non-local causality in modern theories, then you can rest easy knowing there are interpretations of QM and QFT which maintain local causality - perhaps Newton and Einstein would prefer those interpretations.

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    "but it seems like you're saying that modern Quantum Field Theory might be unsatisfying to someone like Newton" Yes... and... "because you think QFT requires instantaneous action at a distance" No to that one. I read somewhere he expects at its core to find some sort of clock-work-like-mechanism. I think he was expecting more physicality that the fields suggest or offer or include. But that is my opinion of his probable thinking/reaction... I do not claim to know such. Mar 8 at 12:40
  • Per the QFT fields. I do not object to their math, or their characteristics or properties. I do not expect they are fundamental. I suspect them to be emergent as they show us "forces" are emergent from "fields"... I expect the "fields" are emergent within a "lattice"... and that an exclusively-physical-fundamental-"lattice" is the only non-crank solution to the question. Because lattices trump fields which trump forces which are akin to magic philosophically. Mar 8 at 12:43
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    I read somewhere he expects at its core to find some sort of clock-work-like-mechanism. - then he can find that in the schrodinger equation, which evolves the wavefunction deterministically over time, like clockwork. @AlistairRiddoch
    – TKoL
    Mar 8 at 12:54
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    I think he was expecting more physicality that the fields suggest or offer or include. - I don't personally have any reason to think that the things we intuitively think of as 'physicality' - usually macroscopic objects made of many atoms, right? - can't be composed of the "stuff" of quantum mechanics. It actually makes intuitive sense to me that physical stuff is made of stuff that seems not-quite-so-"physical". @AlistairRiddoch
    – TKoL
    Mar 8 at 12:55
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    @AlistairRiddoch you lost me.
    – TKoL
    Mar 8 at 14:08
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Classical metaphysics traces back to Plato and Aristotle, and had no trouble at all with ascribing intentionality and actions at a distance to matter.

From the context of the comments, what the questioner really seems to mean by "classical metaphysics" is the early enlightenment theory of causation, which required contact between solids, and could only involve mechanical pushing.

Prior to Newton, physics had already refuted this theory of causation. "Contact" and "pushing" are only valid for macro scale solids that have no interpenetration. The characterization of liquids, and wave behavior, REQUIRES superposition and interpenetration, and this was known prior to Newton discovering attractive forces that act at a distance. Newton's discovery of gravitational attraction was the final nail and thoroughly refuted the solid/contact/mechanistic model of causation, and opened the door for all sorts of forces and methods of interaction to be viable. Electricity, and magnetism and dark energy driving a varying Cosmological constant, all take full advantage of this.

Basically, if we can build any model that works with our data and is testable, we are now free to postulate any sort of cause. We do not anymore have a constrained model for causation.

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  • Yes. That one... the contact and pushing one. Physical. The one you suggest has been "refuted" and dismissed and I guess asserted to be impossible. Is there a term or title or something for that level of physicalism... where it means... exhaustively and exclusively physicalyy to the exclusion of all else, fundamentally. Well... physical, and in motion, and interacting physically (but frictionlessly)... that one.. is there a "label" of "classification" within philosophy, so I know what "sub-room" to ask about such notions? Physicalism Purist? Mar 9 at 20:57
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    @AlistairRiddoch the term I have heard used is "mechanistic causation".
    – Dcleve
    Mar 9 at 23:08
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    MUcho gracias... I will look it up... it is much easier to confirm suggestions, than to try and find a word you dont know to describe a type of thinking that isnt thought. Mar 9 at 23:13
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Since at least the early 20th century, physicists have learned that when they're trying to be especially careful, they have to talk about reality like so:

Reality is such that this model lets us describe it. Given these measurements, we can predict those measurements.

And not like this much more natural way of talking:

This is a so-and-so. It does such-and-such. It is governed by such laws.

This natural and useful way of talking applies metaphor and anthropomorphism until everything is represented in your mind by a tiny invisible version of a macroscopic object. The tiny invisible macroscopic object is imputed with agency and a strong sense of civic duty, and it emanates a magical aura which affects the sense of civic duty of other tiny invisible macroscopic objects. This sounds ridiculous when you express it like this. It is ridiculous. It is also super useful most of the time, so don't knock it. Outside of mathematics, it's best thinking tool we have.

It just falls apart when you get mugged by quantum mechanics. Hence the dividing line between classical physics and modern physics. Classical physics ends where its paradigm stopped being compatible with the models needed to make true predictions.

Why would particles interact at a distance, through the lens of classical physics? Because a disembodied idea with personal agency and a strong sense of civic duty is filling the space, and when a tiny invisible macroscopic object with personal agency sees the disembodied idea with personal agency created by another tiny invisible macroscopic object with personal agency, its sense of civic duty makes it want to act that way.

If it's stupid and it works...

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Let's take a couple of those classical metaphysical lenses and fit them into a tube. Now we have a classical metaphysical telescope, with which we will look for truth throughout the classical metaphysical universe- which is a human construct.

Now note that there is no correspondence between that universe and the one we physically inhabit, which in addition to not being a human construct (it is there whether or not we are), also is the one that contains evidence of fields and quanta and causal relationships.

With a classical metaphysical telescope, we are free to imagine anything we wish to see and not imagine anything we wish not to see, within the classical metaphysical universe. This means that the classical metaphysical world has nothing valid to assert about what can or cannot exist in the actual physical world- including whether or not action at a distance across a void in the physical world is plausible in the metaphysical world.

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