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I really don't know much about philosophy, but my question is whether philosophers have a notion of "physically exists" and what it would mean.

I would say it's clear that a particle like an electron or a quark physically exists.

It's also clear that things like the second law of thermodynamics do exist but they do not physically exist.

Specifically, I want to know if philosophers would say an electromagentic field physically exists. (I'm taking electromagnetic field to be the thing through which light particles travel).

  • It does if you believe in the usual electromagnetism theory that uses this concept to make sense of what we call electromagnetic phenomenon. Otherwise, feel free to deny it and propose something better. – sure Sep 6 '15 at 22:58
  • "Exists" is a tricky word ... The question if a field "physically exists" can be answered from the point of view of physical theory the answer is clearly : YES. 1/2 – Mauro ALLEGRANZA Sep 7 '15 at 9:46
  • From a more "philosophical" point of view, I strongly suggest the insightful book : Ian Hacking, Representing and Intervening (1983) : "If you can spray them, then they are real [said of positrons]". This statement can be easily adapted to field ... 2/2 – Mauro ALLEGRANZA Sep 7 '15 at 9:55
  • Okay, I'm going to try to edit your question and make clearer what I take you to be asking... then I'm going to reopen and hope that fsm helps bring some good answers. – virmaior Sep 7 '15 at 12:13
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    There is always a problem when you get to the "most fundamental" level of existing things. Until you have a next step down, hard to say that that foundational level also "exists." Here's a good, nontechnical discussion of field ontology from geography, but useful for any "field." ncgia.ucsb.edu/Publications/Varenius_Reports/… – Nelson Alexander Sep 7 '15 at 19:46
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Philosophers and scientists came up with multiple definitions of "exist" or "physically exist" over the centuries. If there is a common thread to all of them it is that what "exists" depends on the mode of thinking, there is no "existence proper" even with "physically" attached. When we think about, or apply, a physical theory we accept its "ontology" (what is), same as we accept existence of everyday objects in our everyday activities. This is the case most of the time, but sometimes physicists are forced into a different mode, when they need to revise theories. Then it becomes important to distinguish between experimental content of a theory, that must be kept under any revision, from idealizations postulated by it.

It is in this mode that Einstein realized that ether, absolute space, and even individual spacetime points were idealizations in the classical physics, and could be discarded in the new physics. But of course they were that even before there was a need to discard them. Physicists of 19th century believed that light spread in ether, but that was an idealization abstracted from properties of EM waves. In the modern interpretation EM field is self-propagating and there is no need for ether, but EM field is also an idealization. And so are elementary particles, like electrons and quarks. In quantum field theory they appear as placeholders in Feynman diagrams used to compute perturbative expansions, and those lead to notorious divergences when applied to gravity. So quantum gravity description may not involve Feynman diagrams and the particle picture. But that does not have to happen, more often than not there is enough continuity in idealizations that it is enough to modify concepts of what exists rather than discard them. For instance, atoms were imagined in 19th century as indivisible small rigid balls, and we no longer believe those exist, but their quantum successors are close enough to keep the name.

Quine explains it nicely in On What There Is:"Here we have two competing conceptual schemes, a phenomenalistic one and a physicalistic one... The physical conceptual scheme simplifies our account of experience because of the way myriad scattered sense events come to be associated with single so-called objects; still there is no likelihood that each sentence about physical objects can actually be translated, however deviously and complexly, into the phenomenalistic language... Viewed from within the phenomenalistic conceptual scheme, the ontologies of physical objects and mathematical objects are myths. The quality of myth, however, is relative; relative, in this case, to the epistemological point of view." The word "myth" here does not carry a negative connotation, work on mythology shows that since the dawn of civilization myths were instrumental in rationalizing and managing the world by human societies.

3

I will answer for the "physical" aspect (other answers have addressed the "existence" aspect but it seems to me that what you're after is a distinction between physical and unphysical existence, not a definition of existence itself? Even if not my answer will complement the others).

The way you formulate your question makes me think that what you call "physical existence" is what philosophers call "concrete existence" (as opposed to "abstract"). Laws of nature (or numbers) are abstract while objects such as electrons and rocks are concrete.

Our most fundamental concepts are often difficult to define, but there are some candidate criteria for concreteness (all of which can be discussed):

  • existing in space and time
  • entering causal relations
  • being mind-independent
  • being particular rather than universal (as "red" vs "redness")
  • ...

The first two are the most often used in contemporary literature. The third is controversial because some would say that abstract objects, such as numbers, are mind-independent too.

According to these criteria, the electromagnetic field is concrete: it exists in space and time, enter causal relations, is construed as mind-independent and it is a particular.

If now we turn to what philosophers understand by "physical", there are two main approaches:

  • calling physical what is studied by physics (or an ideal, complete physics), and everything that reduces to it
  • having distinctive criteria for physical things, such as: objectivity (mind-independence), reducibility/compositionality...

In any case physical objects will be a subset of concrete objects (or exactly the same set for physicalists), and again, I think we can say that the electromagnetic field is physical according to both approaches: it is an object of physics, and it is supposed to be objective and compositional (you can consider a part of the field in a specific region).

So in all cases it is safe to say that the electromagntic field physically, or concretely exists.

Let me end with a remark: it's not clear, having said that, that electrons or the electromagnetic field (or numbers or laws of nature) really exist. The doctrine that says so is called scientific realism (or platonism for abstract objects), but there are also anti-realist doctrines, such as instrumentalism or empiricism. It is thus more appropriate to say that if the electromagnetic field exists, then it exists concretely/physically. But as far as I understood your question wasn't about existence specifically but about distinct modes of existence, so that doesn't change my answer.

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There are many opinions of what "exists," including some theories that state the mere act of imagining something brings it into existence.

I have found science does well with exacting wordings, so I would give you an alternate wording for EMF which avoids a lot of trouble: "There exists a model of the universe which includes a field known as the electromagnetic field. This model does a remarkably good job of predicting the observations we make in the world. It does so good at making such predictions that it is often phrased as 'existing in the world.'"

To go much deeper, one would have to start looking at how the brain deals with information. At some point, a model can get so deeply embedded in how we think that it is indistinguishable from reality without substantial effort to discern the reality from the model. This appears to be a natural process that everyone goes through. Thus, many may believe the electromagnetic field "exists" merely because they can no longer distinguish it from reality. At such a point, it might be valid to argue that "EMF exists as a feature of our reality for them." without specifying whether it is a feature of our reality for us.

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Can you poke it with a stick? I'd say you can: put a stick in front of a light, it casts a shadow; wave a bar magnet near a coil of wire connected to a bulb and cause it to light up etc. etc. If you can poke it with a stick, it physically exists, c.f. Dr. Johnson's rebuttal of Berkeley.

But now there is the issue of what exactly you mean by electromagnetic field if you mean the mathematical or conceptual description of aspects of electromagnetism, then they only exist in the mathematical/conceptual sense. That doesn't mean that the EM field doesn't exist, since you can still "poke it with a stick", just that, as with most things, we have descriptive maps that are not the territory.

The main reason why physicists ascribe reality to the EM field is because it has energy and momentum (the fact that light travels at a finite speed is also important); you need to account for this fact in order to have a self consistent theory of electromagnetism. If it didn't have energy and momentum, I suspect that most physicists would view the "fields" as mathematical/computational tool and not a physical one.

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Whatever your notion of "exist" might be, you say you are willing to acknowledge that an electron exists. An electron is a disturbance in a quantum field, so a fortiori you believe that at least some quantum fields exist. I can't imagine any criterion by which some quantum fields exist but the electromagnetic field does not. Do you have such a criterion in mind?

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Consider the surface of the sea; we see waves travelling across the surface of the sea and break on the beach.

We can certainly have the sea without the waves; but can we have the waves without the sea - it doesn't look like it.

The sea is the medium by which the waves travel.

Now, one might be agnostic about the existence of the EM field, or of EM waves; but if one is committed to the existence of EM waves as a description of light; then one ought to be also committed to the existence of the EM field - the two concepts hang together in this way.

note

It's worth noting that one can concieve of space as the medium of motion of particles; for from Aristotles Physics, if there is no place then from where does a particle move and to where? This is a line of thought that began with Parmenides and Zeno; and which is rendered more explicitly in Descartes Meteorology; and also note the connection with the above:

"That the earth, water, air and all other such bodies that surround us are composed of many small parts of various shapes and sizes, which are never so properly disposed nor so exactly joined together that there do not remain many intervals around them; and these intervals are not empty but are filled with that extremely subtle matter through the mediation of which, I have said above, the action of light is communicated".

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The appropriate way to figure out whether something exists is whether it features in explanations in a way you can't eliminate. If you try to eliminate parts of your explanation you can't do without, you are just labelling them as not real. The attachment of that label is an unexplained complication of your explanation. See "The Fabric of Reality" by David Deutsch, Chapter 4.

For example, fairies feature in some explanations of the photos of the Cottingley fairies and that sort of thing, but you can explain those photos without fairies. So fairies don't exist.

Does the electromagnetic field exist? If you're doing a calculation of the motion of charges in a region, knowing the initial conditions of the charges is not sufficient to do the calculation, you also have to know initial conditions of the field. So the field plays a role in explaining what is happening in that region and it should be considered real.

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According to George Berkeley, what we perceive, exists. I usually suggest a better formulation: something exists if you can interact with it.

Some remarks about this: first, existence is not space occupation (a common but arguable argument). Second: interaction is a complex feature, but covers perfectly this feature; third, existence is subjective (a consequence of the interactive feature).

In consequence, if we can interact with a field, it exists. If there are other fields we cannot interact with, they don't exist -for now-.

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