I've seen some rather philosophical or interpretational questions pop up lately. These questions tend to get closed very quickly. I'm wondering if this is neccessary, since such questions can have interesting or enlightening answers. This is not about purely philosophical questions, nor about speculative or esoteric stuff, but rather about

  • philosophy of physics/science
  • interpretational issues of physical theories

and to a lesser extent

  • epistemological and philosphical issues, as long as they are relevant for physics.

A couple of examples:

  • Why is the 'multiverse' critized as being non-physical?
  • Is Bayesian 'degree of belief' subjective? If so, how can it be justified?
  • Is the universe infinite? (spatially, or in time)
  • Why can't physics say something about X?

And some real examples (admittedly not the best):

If you find better examples, don't hesitate to append them / comment. I'm posting my opinion as an answer. If you disagree, please don't downvote this question, but the answer. Or better, post another answer. :-)

(Edit: Added some fictional questions for clarity.)

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    $\begingroup$ Related: meta.physics.stackexchange.com/q/80 $\endgroup$ – David Z Aug 3 '11 at 21:22
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    $\begingroup$ I think we should allow some of the questions whose answer is simply that its independent of observables, and/or dependent on interpretations, and this would be the correct answer to these questions. If it cannot even be answered this way then it should be closed. $\endgroup$ – TROLLHUNTER Aug 4 '11 at 11:27
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    $\begingroup$ On reflection I think our definitions of philosophy may differ. Of the hypothetical examples you've posted: #1 has a fine (if not terribly interesting) physical answer; #2 I think is too philosophical (though I'd have to read the question body); #3 can be addressed both through physics and through philosophy, and as long as we stick to the physics it's fine here; #4 may be too vague/open-ended to be appropriate or it might be fine, depending on what X is (and again I'd have to read the question body to say for sure). $\endgroup$ – David Z Aug 5 '11 at 4:43

I'm going to say no, we should not allow philosophical questions for the simple reason that philosophy is not physics.

In particular, we need to make it very clear that there is a distinction between philosophy and physics, and that the former is off topic here. People who are not familiar with what physics really is sometimes tend to ask questions which I believe any of us would agree are actually philosophical in nature and which physics cannot address, for example this one.

Even for questions which are more closely related to physics, those of a philosophical nature tend not to have definite answers. Those are not the kinds of questions we want here, not only because Stack Exchange aims to exclude them by design, but also because physics as a subject does not handle those sorts of questions well - again, by design. It's often said that something that isn't experimentally falsifiable is not science. We've (unofficially?) adopted a version of that guideline on this site because it works well at distinguishing overly abstract questions which are likely to lead to discussions rather than answers.

  • $\begingroup$ @ David Z : I understand this matter has long been resolved, but something just pinched me while reading your answer. You say philosophy is not physics while it was philosophy from which physics emerged and the highest education as of my knowledge is that of Phd that stands for doctor of philosophy, please correct me if I am wrong $\endgroup$ – Rijul Gupta Oct 26 '13 at 17:58

Interestingly, I have been following the philosophy SE, which is still in beta.


I strongly agree with jdm that philosophical views influence the development of physics. I certainly have the impression that quantum physics, for instance, has profoundly strong philosophical underpinnings. Not only that, but the global Lorentz invariance is an extremely philosophical concept, epically when put in the context that it rules out almost every loop-quantum gravity theory that represents the universe with a finite number of nodes. The philosophy board is also entertaining questions about "is the universe isomorphic to a Turning machine?"

I think there is obvious overlap and some amount of overlap should be expected, but let me just get it out there that I think the Physics SE can intelligently answer most of these questions way better than the philosophy SE could, epically if it's about something like the philosophy of quantum physics, a topic which I think would get closed quickly in the current state of things. Thus my present vote would be that we should allow such questions. The right balance is that of more philosophy than the current physics SE entertains.

  • $\begingroup$ Ah, here is a good example of such questions about existence form nothing: physics.stackexchange.com/questions/13013/… Granted, here the question becomes reduced to matter-energy from nothing, space from nothing, etc. $\endgroup$ – Alan Rominger Aug 5 '11 at 2:59
  • $\begingroup$ That's not a philosophical question, though, at least not in my judgment. It's asking about the basis in physical theory of a very strange-sounding statement. (If you consider questions like that philosophical, then sure, we can and should allow some philosophical questions on the site) $\endgroup$ – David Z Aug 5 '11 at 4:35
  • $\begingroup$ Also, good to know that philosophy.SE is a site now... I'd missed their beta launch. I'm sure we'll be dealing with them a fair amount in the future. $\endgroup$ – David Z Aug 5 '11 at 4:38

I would recommend that if there is any doubt about whether to close a philosophical question (and for some of the questions listed by the OP, I don't think there was any doubt - they were argumentative or biased and fishing for a specific answer), we should leave it open for a while. If there are no constructive answers after a reasonable period of time, and the question becomes a futile discussion, then we should close it.


I'd vote for keeping such questions when in doubt - and if necessary editing them for clarification. My reasoning is the following: From a strictly positivist point of view, the only thing that counts it what I can calculate, and how well my models agree with my measurements. However, not every physicist subscribes to such a radical view. Discussions about whether e.g. wave functions are "real" or not might seem moot to some people, but are very important and interesting to others. It comes down to an argument between these two schools.

Closing a question makes a statement for one of these camps, without giving the other the opportunity to answer. I think such questions should not be decided on prematurely by an individual by the closing the question, but they should rather be debated in the answers. (Debated in a form appropriate for a stackexchange site of course: not forum-like, but with two or three well formulated answers, that may take different points-of-view. )

Also, such questions can be very important for the didactics of physics, which I believe also belongs here.

Finally, such "philosophical" views actually do influence the development of physics. Think about the question, which view of classical mechanics is more "fundamental": a description in terms of forces (Newton's axioms) or in terms of energies (Lagrangian mechanics). As long as you are only dealing with simple cases such as inclined slopes, both seem identical. However, the "energetic" point of view, which was regarded as more elegant, turns out to be generalizable to much more complex cases. Or take the cosmological principle, that says that the earth has no special or privileged position in space and time. What might be seen as a philosophical prejudice, actually has a lot of implications for astrophysics. I can think of a lot of examples that have been dismissed as "philosophical" at first but turned out to give deep insights into nature later.


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