Let’s assume there are multiple observers (or perspectives or “cameras”) viewing the world. Every person has one. However, I know that I am one of these observers.

Therefore, there needs to be a flag or property in the world which contains the information needed to tell which perspective my life becomes. In particular, who is me. However, from another person’s point of view, this flag points to them, not me. This is impossible, since this is a universal flag. Hence, I am the only perspective there is.

If we assume, each person has their own world, with their own flags that points to them, then there needs to be another flag outside of this, which tells which world I will be in for the life I’m living now. For another observer, this would be pointing at their world. It is not possible for the flag to take on multiple values.

If the flag can take on multiple values at the same time, there would still need to be another flag, which tells which value I should select from the first flag in order to live the life I live now. So in the end, there will always be one flag in the world that will point to me, and to nobody else. This proves I am the only observer in the world and the world is unique to me.

Where is the flaw?

  • 1
    This is very closely related to this paper: "A Puzzle about Further Facts" link.springer.com/article/10.1007/s10670-018-9979-6 (open access) in which the author makes the analogy to looking in on a simulated world through a simulated creature via a virtual reality device, and pointing out there needs to be code to determine which (one) simulated creature's perspective is being shown. The author discusses in the paper how, if at all, one might avoid a similar conclusion for our own world.
    – present
    Commented Apr 25, 2020 at 14:49
  • 1
    A relevant classic paper is John Perry's "The Problem of the Essential Indexical".
    – E...
    Commented Apr 25, 2020 at 16:17
  • 1
    Seemingly related question, with some good answers: philosophy.stackexchange.com/questions/54717/…
    – Hypnosifl
    Commented Apr 25, 2020 at 17:13
  • Pry explain WTH is a "flag" ?
    – armand
    Commented Apr 25, 2020 at 22:21
  • The electrons running this machine do not have distinguishing features. Yet there are more than one of them, or it would surely stop. Feynman has proposed that they may all be different passes of the same electron back and forth through time. But then they are still identical and yet distinguished by their age, even though that leaves no trace on them, since they don't age. Your indexing flag could have dimensions. To assume you know the form of some metaphysical data structure a priori is not good reasoning. Commented Apr 26, 2020 at 2:17

7 Answers 7


If I understand it, I think this is a very powerful argument and might lead to "open individualism"


I'm having trouble following the details in your argument. Let me phrase it a bit differently and you can clarify if this is essentially what you're getting at.

We have two bodies (or organisms) in the world, B1 and B2. B1 thinks... why am I B1 and not B2... we could have the same world, with the same two bodies, but where I experience it as B2 instead of B1.

So he assumes there's some additional facts about the world that cause this difference. One move might be for B1 to say, I'm actually a soul S1. And there's a soul S2 experiencing B2.

So this gives 2 possible worlds: 1) S1 experiences B1, and S2 experiences B2. 2) S1 experiences B2, and S2 experiences B1.

But this would be a mistake... because now S1 can ask the same question... why am I S1 and not S2... Using the same reasoning as before S1 presumes he's really a super-soul SS1. This leads to an infinite regress.

From my point of view, there are two possibilities:

  1. The subject/content model of experience is somehow mistaken... This whole exercise comes from the view that one can separate the content of experience from the subject. Maybe this separation is mistaken.

  2. There's only one subject of experience as you said. But this need not lead to solipsism (my current perspective is the only one). The same subject may experience all perspectives. That's the open individualism idea.

  • 1
    You are completely right. Both point 1) and 2) can be resolved. Point 1) The world is the same as the experience itself. Point 2) I know I have person A's perspective and not person B, because I'm person A. Hence, all perspectives are my perspective.
    – siamii
    Commented Apr 26, 2020 at 13:38

Following your logic, right, you are the only observer in the world. I see no flaws in your reasoning.

More properly, you are the only subject, and the rest are all objects (including people) with which you interact in your mind. The only history that exists is the one in your mind.

Factually, there is not a world as such. The world is the interpretation we give to the manifold of concepts resulting from perceptions provided by the senses. Kant called the resulting concept, that is, the world, the "phenomenon", or "the thing as it appears", while the enigmatic underlying causes, the "noumenon", or "the thing in itself". A provoking idea to grasp such concepts is this: things don't have colors. Colors are the result of a process in the eyes. So, what we see is not really out there. But this is just the beginning: odors, textures, flavors, temperatures, time, space, etc. don't exist as well. Everything is just a subjective... invention. Check Kant's Prolegomena to any Future Metaphysics.

Therefore, everything that exists is the product of our experience, essentially coming from your sensitivity. If there's "a flag", it is just the product of your creation. Even me, I am just an object of your imagination. You can't get a definitive proof of my existence. Moreover when you can't prove almost nothing: there are no final rule that would allow you to validate any belief of yours. According to Kant, all our knowledge is based on a set of tautologies, like the dictionary is just a set of circular references. In my writings I use to say that 'the subject defines the object'.

  • However if there is no noumenon then the OP is correct. E.g. ref. "Kant supposes two realms, the phenomenal and noumenal. ... Nietzsche rejects [the existence of the noumenal] categorically. “The ‘thing-in-itself’ is nonsensical” (WtP sec. 558). He argues, as much as Nietzsche actually argues, that if we can have no knowledge of this noumenal realm, why are we supposing it even exists? “To assert the existence as a whole of things of which we know nothing whatever...was a piece of naiveté of Kant” (WtP sec. 571)." Commented May 25, 2021 at 14:24

There is one way to prove that I am not the only mind in the world . Take a concept such as love . To feel love is to presuppose that there is person who is the object of my love . Other emotional states imply or presuppose the existence of others . Now imagine that what I say is false . Imagine that I have such states even when there are no others . How then do I come by such states ? It seems absurd to say that I come by them by way of my own mind . To think is to think about something and that something is the cause of my thought .

  • en.wikipedia.org/wiki/Solipsism#Falsifiability_and_testability It cannot be proven that one is not the only mind that exists. It is at least hypothetically possible to obtain evidence that one is the only mind that exists.
    – polcott
    Commented May 27, 2020 at 21:27
  • This is a bad proof. All the people in the universe, including your wife might be robots (thing that you can't know for sure), then, you would love an object, and you still would be the only mind in the world. Moreover, you cannot be sure that things or people exist outside of you. Perhaps you are just a dream of a solitary God.
    – RodolfoAP
    Commented May 23, 2021 at 5:12

I mentioned the paper "A Puzzle about Further Facts" (Erkenntnis, 2019, https://link.springer.com/article/10.1007/s10670-018-9979-6) in the comments above. I think the most relevant passage from that paper is the following. (The context here -- "Case B" -- is that the protagonist, Fonda, is seeing a simulated world through the perspective of a creature, Alpha, but has forgotten that this is the case, putting her in a similar epistemic situation as ourselves. The question is whether she is right to conclude that there are further facts, i.e., that a different perspective, say Beta's, could have appeared to her, and therefore that there is something else to know about the world, like the flag that you mention, with all the consequences thereof.)

Certainly it is true that a different agent’s perspective could be made to appear to her; all this would require is a change to the code governing which perspective is displayed by the VR system. But would she be justified in believing that a different perspective could have appeared to her? Again, it seems that the moment we allow her to remember even just the mere fact that she is in a simulation, even if she remembers nothing else about her identity in the outside world, she can indeed conclude that a different agent’s perspective could have been made to appear to her. But we explicitly rule out such a memory in Case B. Hence, it is not clear that the notion of a different perspective appearing to her makes sense from Fonda’s perspective. For all she knows, she is Alpha, and how could any perspective other than Alpha’s appear to Alpha?

While the author states that this kind of reasoning seems the best way to avoid concluding that there exist further facts (= additional flags) if one seeks to avoid that conclusion, he does not endorse such reasoning either, saying the argument is "in need of further fleshing out" and explicitly leaves open the possibility of concluding that there are indeed further facts.

Also relevant is the paper "Against egalitarianism" (Analysis, 2013, see also https://en.wikipedia.org/wiki/Vertiginous_question) in which the author (Hellie) argues:

The Hellie-subject: why is it me? Why is it the one whose pains are ‘live’, whose volitions are mine, about whom self-interested concern makes sense? That thing there in the objective world: what is so special about it? Why doesn’t some other subject of experience there in the objective world ‘go live’ in this way: for instance, the ‘Chalmers-subject’ out there driving around in the human being whose visage matches a photo on a certain driver’s license bearing the name ‘David Chalmers’—why not instead it?

This "vertiginous question" by Hellie also seems to pose a challenge to "open individualism" and related theories, because those theories still doesn't seem to answer the question: they do not make any deep distinction between (e.g.) Hellie and Chalmers.

As pointed out in the comments by someone else, this question: Why am I this particular human being? is closely related and there are a lot more references there.


I may be missing something essential, but it seems to me that the underlying “issue” here is more or less the issue you raised in your post How can there be multiple "points of view" in the world?.

In response, I would ask you to review Spinoza’s and Leibnitz’s arguments in favor of substance monism: a system where all things are conceived as modes of a single substance. Then consider that solipsism is the philosophical idea that only one's mind is sure to exist. As an epistemological position, solipsism holds that knowledge of anything outside one's own mind is unsure; the external world and other minds cannot be known and might not exist outside the mind.

All of this should be appraised in the context Wittgenstein’s perspective that “Philosophy is [or should be] a battle against the bewitchment of our intelligence by means of language.” (see Philosophical Investigations, sec. 109).

Finally, with Wittgenstein’s caveat in mind, reread @Conifold’s comments in response to your November 2019 post, which, is seems to me, adequately identifies the flaw you seek:

“Not everything included in the world is a "thing", properties and states of things aren't things, and neither are experiences. Points of view aren't "assigned", point of view of experience of point of view is just nonsensical. The paradox is based on first reifying experiences into "things", then separating them from that which they are experiences of, and finally "puzzling" over how to put those back together. Subjective experiences are not "things", they do not float apart from their subjects, so there is no problem of "assigning" them to those either….What I am saying is that "had my subjective experience been the subjective experience of someone else" makes no more sense than "had squares been round". It is oxymoronic, and illustrates our freedom to string words together. But squareness of squares is not detachable from the squares, and we do not go puzzling over squareness and roundness getting "assigned" to squares and circles.”

  • ""had my subjective experience been the subjective experience of someone else" makes no more sense than "had squares been round". This isn't obvious. The content of our experience changes, yet we tend to think there is continuity of identity. So there is at least a strong intuition of separation between the identity of the subject and the contents of experience. If this is illusory then that needs explanation. Say two people watch the same movie in the same environment... it isn't nonsensical to say they had the same "visual experience". Why can't we extend that to all subjective experience? Commented Apr 27, 2020 at 20:41
  • @Ameet Sharma I cannot further elucidate Conifold's comments, neither in response to the earlier question, nor his comments above (which I'd not read when I posted my answer). In response to your specific query, other that to say that your term "same 'visual experience'" is equivocal, ambiguous -- we occupy different seats in the theater (each filming the film from our own embodied physical and psychological "position"), I am myopic, he is color blind and I am neither, etc., I cannot understand the sense/salience of the question. Maybe I am out of my depth.
    – gonzo
    Commented Apr 27, 2020 at 23:47
  • This is all great. The only problem is that "I" definitely exist, because I am here. It makes no sense to ask why a square is not a circle. But if "I" am the square, it makes sense to ask why "I" am not a circle. All this reasoning of squares and circles only applies in an objective world, but not in a subjective one where there is an "I".
    – siamii
    Commented Apr 28, 2020 at 0:20
  • @ Siamii: "if "I" am the square, it makes sense to ask why "I" am not a circle." Does it then make sense to ask why gonzo is not siamii, or his favorite cat, Mingus?
    – gonzo
    Commented Apr 28, 2020 at 0:31

You start with the idea of “I” and imply a continuity of “I” over time. No such thing exists. There is a perspective. Later, there is a different perspective and the previous no longer exist. The new perspective might believe it has a relation to other perspectives. That is your “I”. It is arbitrary.


Simplest solution: There could be no observers in the world.

Normal solution: The "flag" doesn't have to be universal. It could be local to an observer (or perspective). It actually has to have some connection to the observer if they have one to one correspondence.

Strange solution: There could be no "flags" linking observers and perspectives. Each observer observes a random perspective at each given moment. The observer also takes the memory of the perspective and forgets everything about the previous perspective, which is taken by the next observer observing that perspective. How do you know it's not the case?

In any case, it depends on how you define an observer. Note that, if an observer is defined outside the world, there is no evidence that you are an observer, or you are exactly one whole observer. If an observe is defined in the world, it is located someone in the world, the "flag" is most likely in the location address.

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