Some wild metaphysics that seemingly everyone needs to accept?

[Epistemic status: weird philosophy] Here’s a simple argument: How do we know what exists? Well, we don’t - not for certain. Many different possible worlds are consistent with our observations. A lot of those worlds will be ones in which we are “freak observers”: coincidentally arising computations that resemble our coherent experience, with our perception of the external world of humans and Earth, but that fall apart immediately. Boltzmann brains are one type of freak observer - but there are others, like e.g. a storm in the night sky coincidentally implementing the right computation for just a moment. No matter what our larger epistemological and metaphysical framework is (e.g. how much we apply Occam’s razor, like the simplicity prior in UDASSA), it seems like our probability of being a freak observer should be nonzero.[1][2]We can’t definitively rule it out. But freak observers can’t just happen in our universe - they can happen in many possible universes. The condition for it is probably that the universe has a lot of “stuff” / moving components in it so that we, from our perspective, can’t rule out there being some subcomputation with sufficient structure[3] to manifest our experience. So this rules out tiny pocket universes[4] or large but extremely simple ones, but leaves almost all others possible. So for each of these universes, our probability of it being the “true reality”, and us actually being a freak observer in it is nonzero. And this can never be otherwise - it will always seem at least possible to us that we just arose spontaneously in one of these freak-observer-compatible universes, and that the world we think is real actually isn’t. So insofar as we think we can have some effect on these universes even as freak observers (e.g. if we use evidential and/or logical counterfactuals), we will take them into account in our decisionmaking. So, in practice, we will always act as if these universes are real (to some nonzero extent). Therefore, we de facto believe that they exist. Tegmark 3.5 This argument works on some pretty basic assumptions: Caring about the universes in which you are a freak observer. I do think you do - there’s universes in there where all your loved ones are hanging by a thread over a canyon and your action right now just happens to determine whether they fall to their deaths or not. In fact, it seems like you should care a nonzero amount about almost every freak-observer-compatible universe - since, unless it’s extremely small, there will be some chance of other freak observers than you in there, including versions of yourself and all your loved ones. All of this is also what makes this argument still apply if you prefer deriving probabilities from preferences in the first place - a “caring measure” approach, the main alternative to a simplicity prior (like Wei Dai here, the ADT paper, the insight here that you can interchange probability and utility, discussion here, and David Matolcsi’s OSAC). Being okay with blurring the epistemic/ontic distinction. I’m obviously using a somewhat deflationary, pragmatic notion of existence. If we always act to affect these universes, no matter what, it seems to me like they are real to us, for all intents and purposes. What else would existence even mean? (But if you don’t like this, you can leave everything purely epistemic and still reach the takeaway in the addendum.) This is then also a slightly “softer”, more “permissive” notion of existence - e.g. it includes universes that would be logically incoherent or impossible from an omniscient perspective, but which we can’t rule out from our limited, completely a priori perspective.[5] Generally, I think a useful analogy for this kind of “extreme a priori” philosophy (à la Kant or Descartes) are the extreme hot conditions right after the Big Bang, when the four fundamental forces may still have been stuck together as one, and discrete protons and neutrons had not yet constituted themselves out of the quark-gluon plasma soup. Similarly, in the fitful, grasping ignorance of a priori philosophy, the epistemic, ontic, and axiological blur into each other. (see, for example, Wei Dai’s very clarifying What Are Probabilities, Anyway?)[6] (Some weight on) Computationalism about consciousness. I’m not very familiar with non-computationalist/functionalist views of consciousness, but I think something like this argument should actually also go through for a lot of them? Just substitute whatever you think is needed for consciousness for computations, and this will still be able to arise coincidentally in a lot of radically different universes. (Some weight on) Evidential and/or logical counterfactuals, i.e. some acausal reasoning. If you cooperate on the prisoner’s dilemma with a twin, you are doing this. (For the rest of this post, I’m implicitly going to be using evidential counterfactuals since I prefer them, and Abram Demski agrees and says it probably works out to the same thing.) So this se