The classic assumption of physics is that, at some level, things are simple. For a long time, that worked. From F=ma to Maxwell's equations, the basic rules were short, and most results corresponded to those rules. Engineering is based on those rules. Quantum mechanics had people upset for decades, but it was eventually understood reasonably well, and led to another generation of engineering that worked.
But basic physics has been somewhat stuck for decades now. There's still no unified field theory. Smolin is suggesting that maybe there are no underlying simple rules.
[1] https://arstechnica.com/science/2023/01/requiem-for-a-string...
Humans have an intuition for the existence of "material" because on our scale, we can reach out and touch something. But on the femto or atto scale, this does not happen, or when it does happen, we describe it with quantum collision math.
So why cling to this intuition?
I'm simply saying that an immaterial universe with the same properties such that it is isomorphic to the universe that most believe we live in is a better thought experiment to carry in your head. For one, you'll stop thinking "mind body problem, what is mind such that it is not body?" instead you'll say "well, body is not, so it must be the same substance as mind, it's not really that strange after all. It's VMs all the way down"
It's a terribly reductive process. And the foundation of biases is deep and invisible.
Moving in the opposite direction would reveal a lot.
I have to say I'm skeptical when anybody with a background solely in the monasteries of the "materialist interpretation" of the Matrix declares that even energy is a form of matter. There's even a guy in the Matrix who says that so many Matrices have been built within the Matrix experimentally, that with all probability he lives in one of those.
(I'm not just making a formulaic joke; I believe the informational/computational universe is a much better explanation of everything we see. I'm not saying digital computers, or quantum computers, not trying to shoehorn anything; the computer has the nature of our universe. But you know how when we shake hands, at a particle level we have to reinterpret to where our hands don't actually touch, our electrons repel each other, and perhaps some jump the gap? that is more informational than it is material; there is no need for the imagining of material quantum-bollards interacting; we do physics with math (abstract) not billiard balls (physical). Mind-body problem? there is no mind-body problem if the body is as abstract as the mind. Or rather, there still are some mind-body questions, but they doesn't seem as intractable.)