I suppose that’s fair to a point. It’s just disappointing.

The thing is this non material whatever can’t have properties. If it stores information, has state and has consistent behaviour then really it’s just a form of material (in the philosophical sense that it’s a part of the world), so it can’t have any of those. At which point, how does it even interact with the world at all? I mean if it influences the brain, then that mechanism of influence makes it part of the world, right? It makes it material.

That’s where I find the idea incoherent. I don’t see how it can be both immaterial but also have material effects. Doing so makes it material, I think by definition. It means it must be part of material reality in that sense. Or at least I’d like to hear an argument why it doesn’t.

What is the material evidence for numbers? What is the material evidence for logic? What is the material evidence for persistence of identity over time? What is the material evidence for math? What is the material evidence for categories? What is the material evidence for grammar? What is the material evidence for a mayor (not the mayor qua person, but the mayor qua office)? What is the material evidence for marriage? According to empirical evidence, which knife is the best knife? There is no "best" without purpose. And materialism has nothing to say about purposes. Empiricism can only work when an agent in the world has a specific purpose. There are vast swathes of human experience that don't fit tidily in the box of materialism or empiricism.

Those things are behaviours and information that can be encoded in matter. If the non material thing in dualism is just emergent behaviour, then it’s not adding anything beyond what we already have in materialism.

Numbers aren't emergent behavior. Numbers are a metaphysical category. Categories are metaphysical. There's no empirical evidence for order vs. randomness. The concept of "order" doesn't make sense empirically. There has to be a separate, metaphysical value structure that determines whether the data aligns to the value structure or not. Just because you haven't been clear in your thinking doesn't mean metaphysics aren't real or essential to dealing with the physical world.

I accept that. Metaphysics is real in a useful way, but I think that metaphysics itself is an emergent behaviour. Emergent behaviours are behaviours of mater, and matter is real, therefore emergent behaviours are real.

"Emergent behavior" is handwavium materialists use to avoid cognitive dissonance.

We observe them, categorise them, and engineer them all the time.

If the "non-material" is required to explain material phenomena, then it must be causally related to the "material"...but at that point what exactly makes it "non-material" at all?

"Non-material" just sounds like a bad label for material things we don't understand.

We don't understand how our cognition or consciousness works, but it seems silly to assume that because we don't understand we fundamentally can't understand.

People who push the mysterious interpretation of dualism are just trying to find a place for the divine that is separate from the material but in doing so they baselessly seek to circumscribe our capacity to understand.