They are an illusion in precisely the same way your car or your day job are illusions: we don't admit any notion of qualia/cars/day jobs into our ontology of physics, and of qualia must ultimately be explained by appealing only to our ontology.

>the same way your car or your day job are illusions

But what work is calling these things illusions doing for you? That they're not fundamental units of the furniture of the universe doesn't mean they don't exist or play necessary causal or explanatory roles.

> But what work is calling these things illusions doing for you?

It serves to help distinguish that which is reducible to more fundamental ontological entities, from that which is irreducible and thus ontologically fundamental.

I agree that these concepts certainly fulfill useful causal and explanatory roles. Whether they are "necessary" has some room for debate.

How do we know when we have arrived at something that is irreducible?

In a similar manner in which we settle on the primitives of physics theories: parsimony in explaining the available data.

What about "parsimony in explaining the available data" indicates that it is irreducible though?

Every theory posits some axioms. These are irreducible by definition.

The challenge is choosing which axiomatic basis we ought to prefer given our incomplete information. This is answered by induction [1].

[1] https://en.wikipedia.org/wiki/Solomonoff%27s_theory_of_induc...

What you're describing is "the best way to do science, so we can make some progress". That's all well and good but what other people are talking about is the nature of reality which, in pursuit of, those crazy people, they are perfectly willing to doubt axioms.

As well they should and as is their right since a set of axioms are effectively ground facts which are selected to make logical reasoning across a domain possible, nothing more.

That doesn't make them true in the big sense of True, it makes them expedient, productive of theory, generative, a lot of wonderful things, maybe even strongly implied by all evidence, but not apriori true. They're dubitable.

> That's all well and good but what other people are talking about is the nature of reality which, in pursuit of, those crazy people, they are perfectly willing to doubt axioms.

Solomonoff induction does doubt and change axioms. It's a fundamental part of the whole process in fact.

> That doesn't make them true in the big sense of True, it makes them expedient, productive of theory, generative, a lot of wonderful things, maybe even strongly implied by all evidence, but not apriori true. They're dubitable.

Logic is used to make distinctions. Two theories with differing axiomatic bases will make different distinctions, but if they make the same predictions in all cases, then they are logically the same, ie. there is a fundamental isomorphism between them. In this case, it literally doesn't matter if one is "actually really true", and the other is a mathematical dual of some sort.

For instance, polar and Cartesian coordinates are completely equivalent. A theory cast in one might be easier for us to work with, but even if reality really used the other coordinate system, it quite literally doesn't matter.

In the case when the two theories do differ in their predictions, we should epistemically prefer one over the other, and Solomonoff Induction shows us how to do this rigourously.

Someone, a woman, I forget her name, a physicist has lately questioned the parsimonius assumption or more accurately the whole beauty assumption, meaning, roughly, the most beautiful or parsimonious theory is correct. Just a data point to this conversation, not an argument.

Re: Solomonoff, if you're chucking away unnecessaries, which is what I understand Solomonoff to be doing (I had to be reminded what his theory was truthfully) then that's all well and good, let's chuck. But you still are left with the problem of whether the axioms are true. That's a different thing entirely except to the extent we define true operationally, as having predictive power over the things we understand and know about in the way we understand them.

We moderns are all deeply enmeshed with Scientism which is an ism that says logic and reasoning and the scientific method etc. are the only valid tools for aquiring certain (indubitable) knowledge. What if it's just not true ? Then what ?

So, is this to say we approach the irreducible best with induction?

You can only really "experience" the model your brain makes of the world, not the world directly. You end up assuming the world exists and there's no Descartes' Demon.

Right... we are just colonies of cells which behave in programmed ways to generate predictable responses from other cells in other parts of the colony who have their own jobs to perform in maintaining the homeostasis of the colony. The illusion of self is useful because it ensures that the collection of cells entrusted with executive functions act in the interest of the entire colony by perceiving it as a unified whole.

Another way to put it: the experience is real, but it might be misleading.

A hallucination is an experience of something that doesn't exist, but the experience itself does.

Misleading in some respects, but overall helpful. Like a computer desktop.