I'm not certain this comment will be coherent, but I would like to compose it before I lose my train of thought. (I'm in an atypical mental state, so I easily could forget the pieces when feeling more normal.) The writing below sounds rather choppy and emphatic, but I'm actually feeling neutral and unconvinced. I wonder if anyone would be able to 'catch this train' and steer it somewhere else perhaps..?

It's an argument for dualism. Here is some background:

I've always been a monist: believing that everything should be coherent from within this reality. This is the idea that if things don't make sense, it is due to limited knowledge and a limited brain, not an incomplete universe. (Where the universe is the physical material world.)

While composing Less Wrong comments, I've often thought about what an incomplete universe would look like. (Since this is what dualists claim -- what do they mean by something existing differently or beyond material existence?)

I've written before that a simulation (a simulation is a reality S that is a subset of something larger) is just as good as (or the same as) "reality" if the simulation is complete within itself. That is, if an agent within the simulation would find that in principle everything within the simulation is coherent and can be understood from within the simulation. Importantly, there is no hint within the simulation of anything existing outside the simulation. (For example, in the multiple worlds theory, if the many worlds don't interact, each world is its own independent complete reality. The worlds are simulated within a larger entity of all the worlds.)

When physical materialists claim that the physical material world is our entire reality, they are claiming that the physical material world is a reality X, and you cannot deduce anything beyond X from within X. That is, there doesn't exist anything but X, as far as we're concerned. (We can speculate about many worlds, but unless the worlds interact, one world cannot deduce the others.) I've always found this to be obvious, because if you can deduce anything beyond X from within X, then what you've deduced is part of the physical material world (because you deduced it, through interaction) and it's part of X after all.

(end of background material)

It just occurred to me that we do have evidence that our physical material world X is incomplete. So I've stumbled on this argument for dualism. It's actually a very old one, but approached from a different angle. As I said, I stumbled upon it.

It's the problem of existence. Being a monist means believing that if things don't make sense, it is due to limited knowledge and a limited brain. But the problem of existence is such that no amount of knowledge will solve it: there's nothing we could ever learn (or even believe) within X that would solve this problem. Not a complete understanding of the physics of the beginning of the universe. Not even theism!

I cannot understand what the answer to the problem could possibly be, but I think that I can understand that there is no answer possible within X. So to the extent that I am correct that this problem is not in theory solvable in X means that X is incomplete.

I could be incorrect about whether this problem is in principle unsolvable in X. But I am relatively certain of it, on the same level as having confidence in logic. If I lose confidence in logic, I have nothing to reason with. So for now, I would find it more reasonable to guess that I'm in a simulation of some kind where this particular conundrum is embedded. X is a subset of a larger reality Y where existence is explained.

Given what we know about X, and the problem of existence, what can we deduce about the larger universe Y where existence is explained? Anything? What about deducing anything from the peculiar fact that X is missing information about existence?