Recently, I read an article that implied if the many-worlds interpretation is true, than so is quantum solipsism. Here's the article for reference: https://millenniumconjectures.com/2013/11/16/conjecture-5-quantum-solipsism-part-one/

I don't entirely understand what the author is trying to get at- does he mean that if the many worlds interpretation is correct, then I am the only conscious being in each of the universes I experience? And how would that work?

Or is quantum solipsism different than regular solipsism, and I'm not understanding what he's trying to get at?

And I do understand, of course, that I will never technically know if solipsism due to the MWI is real, seeing as you all could be figments of my imagination and are lying when you respond, haha. But putting that aside, what do you guys think?

  • I suspect that by "quantum solipsism" the author means that from the perspective of any given mind, all other minds should be seen as being in some degree of quantum superposition rather than in an exact state, as in the many-minds interpretation which may actually be closer to what Everett intended (he did not originally call it the 'many-worlds' interpretation). So it wouldn't be that the people you interact with are p-zombies, but rather that you are in some sense interacting with multiple slightly distinct variants of other people.
    – Hypnosifl
    Jun 4, 2021 at 16:15

2 Answers 2


Physics of course has no model of consciousness, so the MWI can't say anything about it directly, but the idea that different people are conscious in different worlds is, at the least, very much against the spirit of the MWI.

The idea of the MWI is that all of the worlds are real, and they differ only in the outcomes of past measurements, and consequences of those outcomes. There's no reason why finding that an electron's spin points up would turn Alice but not Bob into a philosophical zombie, while finding that it points down would turn Bob but not Alice into a p-zombie – which is what would have to happen for each of them to see only one measurement outcome.

millenniumconjectures.com is just some guy's personal blog, and he doesn't appear to have any expertise in physics, so I don't think there's any need to search for a deeper meaning in the blog post. It's just wrong.

  • So what you're saying is that in both the world where the electron spins up and the one where it spins down, both people are still conscious? I figured as well, just wanted to check seeing as I too, have no physics background whatsoever. I really couldn't even make heads or tails of the blog post, the only thing that seemed to spell a clear message was the title.
    – VKH
    Jun 3, 2021 at 23:50

According to Everett's seminal paper "The Theory of the Universal Wavefunction", the Many Worlds Interpretation is motivated by considering the problem of multiple observers in the universe. From the Introduction of this paper:

The question of the consistency of the scheme arises if one contemplates regarding the observer and his object-system as a single (composite) physical system. Indeed, the situation becomes quite paradoxical if we allow for the existence of more than one observer. Let us consider the case of one observer A, who is performing measurements upon a system S, the totality (A + S) in turn forming the object-system for another observer, B.
Here in defense of his considerations, Everett starts with the notion that treating a single observer as special leads to some problems when you add in another observer; in this case, the original observer A is observing system S, and some other observer B observes A and S together.

This core of the introduction is based on the idea that there are two processes (using Everett's labeling): Process 1, an indeterministic process, is probabilistic and occurs when an observer makes an observation; and Process 2, a deterministic process, occurs when observers are not looking. Process 1 is a reference to the Born Rule, the probabilistic outcome that occurs due to wavefunction collapse. Process 2 is a reference to the Schrodinger Equation. Loosely, Everett considers that when B observes A+S (observes A and his observations of S), then B is compelled to use Process 2 to describe the situation. But when A is just observing S alone, A is compelled to use Process 1. This leads to the paradox Everett introduces. The MWI stems from resolving this paradox by rejecting Process 1 (meaning, rejecting that it's a "real" thing).

For example, if Everett is observing Schrodinger opening his box, then to Everett, there appears to be a superposition between Schrodinger seeing a living cat and Schrodinger seeing a dead cat. In the spirit of the paper, Everett then concludes that this is the actual reality... there's a universal wavefunction here that is in a superposition between Schrodinger seeing a living cat and Schrodinger seeing a dead cat. The Schrodinger that sees a living cat simply doesn't interact with the Schrodinger that sees the dead cat, but they both exist in a universal wavefunction.

I discuss this here so you can see how the assumption that particular observers aren't special leads to the MWI through Everett's eyes (and you can walk through the introduction to Everett's paper and compare to this description if you like). Compare that to this from the blog:

It’s as if our observations roll the quantum dice and influence which course through the multiverse each individual consciousness takes
Sackler here is treating not just the particular branch he's on as special, but the path "through the multiverse" leading to that branch as special. Suffice it to say this adds to the MWI. But more to the point, given this view of MWI's core justification (at least as given in Everett's introduction), it seems to conflict with the "spirit" of MWI in the sense that MWI is questioning the notion that particular observers are special, yet Sackler is presuming that very thing.

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