My larger question is this: "Can (physical) space exist without perception?"

I'm especially interested in a smaller question that I believe addresses the larger question, which is: "Is there a level of analysis (or resolution) at which energy and matter are indistinguishable?"

For some context, Christian Norberg-Schulz writes about architectural space:

"It is impossible to discuss architectural space systematically when perceptual space is taken as the point of departure. What one describes in this way are subjective architectural experiences, and one would have to arrive at the absurd conclusion that 'architecture comes into being only when experienced.'" (Existence, Space & Architecture, p. 13)

Norberg-Schulz concludes that physical space existing only in the presence of an observer is "absurd", but I'm not sure it is. At a certain level of analysis, two perceptually distinct things might become indistinguishable. For instance, at the atomic level, a chair and a table are indistinguishable.

My understanding is that if you zoom in to the lowest level of analysis (the hypokeimenon, if I'm interpreting that correctly), current physics understands this to be some kind of quantum flux of interacting fields. If at this level anything is indistinguishable from anything else, I think it's fair to say that physical space cannot be said to exist, and does require some observer to afford it reality. (Or, more accurately, there would only be a single space, and it would be the whole universe; any discretization of this would require emergent properties at higher levels of analysis.)

However, I'm unsure if—even at the lowest level of analysis—matter and energy are actually indistinguishable. If matter and energy are always distinct from one another, then no matter how far you zoom in (even at the hypokeimenological level), the patterns of matter and energy in the universe necessarily give form to something that can be interpreted as physical space independent of observation.

The obvious answer might be: "If everything is indistinguishable, you're looking at the wrong level of analysis!" While I agree, I'm interested in the alternative.

Forgive me if this is more of a physics question than a philosophy question, and please let me know if anything is unclear.

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    Are you thinking along the lines of Monadology? " To Leibniz, space and time were an illusion, and likewise substance itself. The only things that could be called real were utterly simple beings of psychic activity 'endowed with perception and appetite.'" See also subjective idealism.
    – J D
    May 22, 2023 at 19:38
  • I have long wondered why there are not more solipsists.
    – Boba Fit
    May 22, 2023 at 22:00
  • 1
    @BobaFit, I went to a solipsists convention once. I couldn't understand what all those other people were doing there. May 23, 2023 at 4:15
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    What physical space? Exist for whom? There is no existence bereft of the observer. Even if you imagine a physical space without a observer, still you are the observer of your imaginary idea. Observer is always there. May 23, 2023 at 19:01
  • 1
    Blackholes seem to literally merge matter & energy, into a superfluid: 'Turbulent black holes grow fractal skins as they feed' newscientist.com/article/… You might like this answer: 'Is the idea that "Everything is energy" even coherent?' philosophy.stackexchange.com/questions/85899/…
    – CriglCragl
    May 23, 2023 at 22:53

4 Answers 4


If you heat matter to a high enough temperature- as existed in the first moments of the big bang- then the distinction between matter and radiation fades away, and physicists deal mathematically with the high-energy soup that results as if it consisted entirely of radiation. Lowering the temperature then causes the matter and radiation to become distinguishable, and they must be mathematically accounted for separately.

Physical space persists even though there might be no one on hand to perceive it. This has nothing to do with whether or not we are able to draw distinctions between matter and radiation.

  • Great answer! How do we know that physical space exists irrespective of matter vs. radiation/energy?
    – 40EridaniB
    May 24, 2023 at 19:12
  • @40EridaniB, spacetime is the stage upon which particles and waves and fields and energy and matter act out their script. without that stage, there would be no play. Physics people have models for spacetime which comport well with observation and experiment, and which mathematically exist even in the absence of the players- a condition called the vacuum state. May 25, 2023 at 4:45

The Strong Mystical Case for Idealism

The Buddha describes the metaphysical observation called dependent origination.


The principle of Dependent Origination is that when anything arises dependent on particular conditions, it ceases with the ceasing of those conditions.

The perceptive context (zoom-down to quantum models; or zoom-out to expanding universe; or zoom-backward to the big bang singularity) arises in the mind along with the perceptions and concepts that are considered to be attributes of "reality".

  • Very interesting! If space is dependently organized on distinguishability between matter and energy then it must disappear if they become indistinguishable
    – 40EridaniB
    May 23, 2023 at 1:33
  • Si, I believe that's what the sophos on the mountain once told me! I don't question sophī.
    – Hudjefa
    May 23, 2023 at 6:37

The Standard Model distinguishes fermions from bosons, although the principle of distinction allows that composites of fermions can be bosonic and vice versa. But so per elementary fermions and bosons, the former roughly equate to "matter" and the latter to "energy" (or force, rather).

The fields at issue can also be differentiated by whether they are vector fields or scalar, with e.g. the weak force being "vectronic" (so to speak) whereas the Higgs field is (so far as we are aware) uniquely scalar. Quite roughly, a vector field involves excitations whose locations are mapped by vectors, while a scalar field's excitations are mapped by crests and troughs.

The photon field decoupled from the other elements of the weak field long ago, so photons are fairly similar to weak vectrons in various ways. (I apologize again for using that word "vectron" but I don't remember the mainstream name, I think they usually just say "weak bosons" because the emphasis is on the weak-force example.) Still, photons have no internal mass (they can "assume" mass in concert, as with kugelblitzes) whereas there are massive weak vectrons. Gluons have no internal mass but can, ex hypothesi, form massive glueballs. Gravitons are typically assumed to be massless although I think this is a technically open question.

Leptons have mass, but this varies from elementary lepton type to type. So leptons can be distinguished by their mass, for example.

Now, theoretically, all the fields were at some point fused as inflatonic. I don't know if the decoupling is supposed to have been absolutely universal or whether there might be primordial inflatons that survived the initial expansion, but at any rate, per the decoupling, we can differentiate the separated fields from the concept of the inflaton field.

The problem of quantum gravity, or gravitons as excitations of a dedicated quantum field, is unsolved as of yet. Insofar as gravity has the more definitive relationship with the overall manifestation of spacetime (per relativity), the question, "Does spacetime exist apart from perception?" would, as a quantum-theoretic question, be equivalent to, "Does gravity exist apart from perception?"

On the philosophical side of things, Immanuel Kant argued that we have an inherent concept of a generalized scalar field (not his terminology, but you'll recognize the overlap) filling all space:

If all reality in perception has a degree, between which and negation there is an endless sequence of ever smaller degrees, and if, nevertheless, every sense must have a determinate degree of receptivity for sensations; no perception, and consequently no experience is possible, which can prove, either immediately or mediately, an entire absence of all reality in a phenomenon; in other words, it is impossible ever to draw from experience a proof of the existence of empty space or of empty time. For in the first place, an entire absence of reality in a sensuous intuition cannot of course be an object of perception; secondly, such absence cannot be deduced from the contemplation of any single phenomenon, and the difference of the degrees in its reality; nor ought it ever to be admitted in explanation of any phenomenon. For if even the complete intuition of a determinate space or time is thoroughly real, that is, if no part thereof is empty, yet because every reality has its degree, which, with the extensive quantity of the phenomenon unchanged, can diminish through endless gradations down to nothing (the void), there must be infinitely graduated degrees, with which space or time is filled, and the intensive quantity in different phenomena may be smaller or greater, although the extensive quantity of the intuition remains equal and unaltered.

I.e., a perfectly empty space/time would be empty of causality, of all energy/force as well as all matter, and so it would not be able to cause us to perceive itself or its emptiness. If we have been caused to perceive some space/time, then, the source of that perception has at least some nonzero "degree of reality" (scalar excitation).

If human brains, with all their molecules, are what perceive spacetime, then for spacetime to depend on perception would seem to mean that spacetime depended on brains. On the other hand, what is called "the hard problem of consciousness", being unsolved to date (or: there's no stable consensus about whether it can be or has been solved), keeps open our inquiry into whether brains or indeed any physical matter-and-energy/force arrangement is absolutely required for perception as such. For example, Kant thought that transcendental apperception is simple in a way inconsistent with space being an absolute foundation for reality (since he said that nothing substantially existent in space is transcendentally simple).

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    +1 This post invokes language that is compatible with "substance", "active force", and "transcendental idealism".
    – J D
    May 23, 2023 at 16:52
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    Very good answer, and fascinating point about Kant and "degree of reality"!
    – 40EridaniB
    May 24, 2023 at 19:16

To expand on the excellent answer already provided, according to mainstream science the Universe had existed for more than 13 billion years before the life on Earth evolved complex powers of perception. Even without that knowledge it should be clear that there are no grounds for assuming that space and time cannot exist without perception. If you suppose the contrary, logic will lead you to all sorts of absurd conclusions. Clearly it is true that perception is required to appreciate and understand space and time, but that is a different point.

Matter and energy are inter-related, in that either (in the right quantities and circumstances) can be converted into the other. The massive particles that comprise matter and the massless particles that are pure energy behave in quite different ways, and they can be distinguished accordingly. Your idea that they might become indistinguishable if one 'zooms in' to a sufficient degree is undermined by a number of constraints. The first is that as far as we know, energy and matter are quantised, which means that there is a hard limit on how far you can 'zoom in' before the granular nature is apparent. Also, there are a number of 'uncertainty relations' within quantum theory which mean in effect that there is an inherent fuzziness to any pictures of matter and energy we might try to imagine in an everyday sense.

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