Solipsism is Underrated

Nice post. I tend to think that solipsism of the sort you describe (a form of "subjective idealism") ends up looking almost like regular materialism, just phrased in a different ontology. That's because you still have to predict all the things you observe, and in theory, you'd presumably converge on similar "physical laws" to describe how things you observe change as a materialist does. For example, you'll still have your own idealist form of quantum mechanics to explain the observations you make as a quantum physicist (if you are a quantum physicist). In practice you don't have the computing power to by yourself figure all these things out just based on your own observations, but presumably an AIXI version of you would be able to deduce the full laws of physics from just these solipsist observations.

So if the laws of physics are the same, the only difference seems to be that in the case of idealism, we call the ontological primitive "mental", and we say that external phenomena don't actually exist but instead we just model them as if they existed to predict experiences. I suppose this is a consistent view and isn't that different in complexity from regular materialism. I just don't see much motivation for it. It seems slightly more elegant to just assume that all the stuff we're modeling as if it existed actually does exist (whatever that means).

And I'm not sure how much difference it makes to postulate that the ontological primitive is "mental" (whatever that means). Whether the ontological primitive is mental or not, there are still mechanical processes in our brains that cause us to believe we're conscious and to ask why there's a hard problem of consciousness. Maybe that already explains all the data, and there's no need for us to actually be conscious (whatever that would mean).

Anyway, I find these questions to be some of the most difficult in philosophy, because it's so hard to know what we're even talking about. We have to explain the datum that we're conscious, but what exactly does that datum look like? It seems that how we interpret the datum depends on what ontology we're already assuming. A materialist interprets the datum as saying that we physically believe that we're conscious, and materialism can explain that just fine. A non-materialist insists that there's more to the datum than that.

Note that if someone assigns probabilities to these models, and conditional outcomes based on what they say publically, materialism is far more beneficial to express than solipsism, even if one finds solipsism more likely.

In the case where materialism and some form of causality is true, then you have some impact by publicly supporting it and pushing other people toward it. If instead, solipsism is true, and you push these hallucinations you call "other people" toward it, you get no benefit.

Much like other questions of free will and causality, as long as I assign some chance that it's real and I have choices that matter, I should behave as if that's certain. Even if I privately am not convinced, there's no benefit to acting that way.

I don't know whether you missed this or just didn't spell it out, but the reason that the likelihood ratio is so much in favor of materialism over solipsism is that if solipsism were true, you could experience literally anything, and apparently ordered universes consistent with simple physical laws are a vanishing subset of the possible experiences.

You'd need a solipsist theory that strongly predicts ordered universes without adding in too much complexity, just in order to be in the conversation with the likelihood of qualia being reducible to materialism.

"Qualia being irreducible" is, to be as charitable to you as possible, in the reference class of philosophical positions that some people have seen as unassailable and others have seen as flawed. You don't get to assign incredibly high probability within this reference class.

(To be uncharitable, it is an intuition for which you cannot provide even what looks like an airtight philosophical argument, just louder reiterations of your intuition.)

But using either interpretation, how puzzling is the view, that the activity of these little material things somehow is responsible for conscious qualia? This is where a lot of critical thinking has led many people to say things like “consciousness must be what an algorithm implemented on a physical machine feels like from the ‘inside.’” And this is a decent hypothesis, but not an explanatory one at all. The emergence of consciousness and qualia is just something that materialists need to accept as a spooky phenomenon. It's not a very satisfying solution to the hard problem of consciousness.

"lack of a satisfying explanatory solution" does not imply low likelihood if you think that the explanatory solution exists but is computationally hard to find (which in fact seems pretty reasonable).

Like, the same structure of argument could be used to argue that computers are extremely low likelihood -- how puzzling is the view, that the activity of electrons moving around somehow is responsible for proving mathematical theorems?

With laptops, we of course have a good explanation of how computation arises from electrons, but that's because we designed them -- it would probably be much harder if we had no knowledge of laptops or even electricity and then were handed a laptop and asked to explain how it could reliably produce true mathematical theorems. This seems pretty analogous to the situation we find ourselves in with consciousness.

You haven't addressed the "what's so special about you" objection.

Suppose that you update on the evidence that you experience conscious qualia

What exactly would it mean to perform a baysian update on you not experiencing qualia?

The only ontological primitive is my own mind.

The primitives of materialism are described in equations. Does a solipsist seek an equation to tell them how angry they will be next Tuesday? If not, what is the substance of a solipsistic model of the world?

This belief in some mysterious ability for the mental to supervene on the physical

I am not sure what you mean my that, I consider my mind to be just an arrangement of atoms. An arrangement governed by the same laws as the rest of the universe.

how puzzling is the view, that the activity of these little material things somehow is responsible for conscious qualia?

I am not sure where the instinct that consciousness can't be materialistic comes from, although I would suspect that it might come from a large amount of uncertainty, and an inability to imagine any specific answer that you would consider a good explanation. Wherever this instinct comes from, I don't think it is reliable.

You know that "if a tree falls in a forest, and there is no one there to hear it, does it make a sound? [? · GW]" thing. Even after all the factual questions, like if audio equipment would record something, have been answered, there is a feeling of a question remaining. I expect any explanation of qualia to look somewhat similar, a description of how mental imperfections produce a sensation of something.

Consider the limiting case of describing minds in terms of algorithms, you scan a philosophers brain, put the data into a computer, and predict exactly their discussion on qualia. Once you have a complete understanding of why the philosopher talks about qualia, if the philosopher has any info about qualia at all, the process by which they gained that info should be part of the model.

Pick something up, drop it, watch it fall. Can solipsism consider this observation to be more likely than some max entropy observation? How does a solipsist predict the experience of watching the object fall.