Put it this way: we are not clear really on what the difference is between ‘experiencing qualia’ and ‘receiving and responding to external stimuli’
Like, you might be convinced you possess ‘qualia’, and you might believe the same applies to me, or a dog, or a mouse… or a fish… but what about an ant? A plant? A bacterium? A neuron? A piece of semiconductor?
Somewhere along that continuum you probably say ‘yeah, there, that thing is experiencing qualia’. But why there? Why anywhere?
Some people think that whether something experiences qualia depends on it having the right kind of complexity. For those people, looking along that continuum, they might just say that ALL those things experience qualia, but that the richness of that experience varies according to the appropriate complexity.
For some of us, though, whether or not a thing experiences qualia depends primarily on whether there is a mental substance involved. A computer has no mind (we suspect), and so even if its complexity (of the alleged 'right sort') exceeds that of the human, there is still no experiences.
The main point I'm making here is that trying to draw attention to this continuum is only going to be a persuasive argument to those who already think (or are inclined to think) that the ability to have experiences of qualia comes about merely from having the right kind of complexity (e.g., 'receiving and responding to external stimuli').
I am inclined to think that other humans and other non-human animals have experiences, but I don't think that's merely because they're complex enough systems (of the right sort of complexity).
Each view of the world has things it explains well, and things it struggles to explain. Some views do a better job overall than others.
In terms of idealist and dualist views of reality, the claims that there's fundamentally just minds, or fundamentally both minds and physical stuff, are very likely to entail that there is some kind of ensoulment that happens. Perhaps it's required for these views.
While I lean towards a type of idealist view myself, and I think overall it does a better job of explaining various matters than a physicalist view, how exactly ensoulment works is one of the places where these views are at their weakest. I don't think there's any contradiction here or problem for a view like mine, I just think that the physicalist account does a nicer job of explaining things in this specific corner. But that point in physicalism's favour here isn't enough to balance out the places it doesn't do so well (e.g., its complete inability to even begin to explain qualia).
The core point of my post though was that pointing to the continuum of complexity is an argument that would only have weight with people who already have a particular belief in common with you -- that is, that physical complexity of the right sort is somehow relevant to the question of whether something has experiences.
The whole point of introducing the (icky) "qualia" concept is that it's not the same thing as appearing alive to external observers.
As I understand things, we have no way of knowing the answer. So there's no point in assuming in either direction (unless that makes you feel more comfortable).
Personally I avoid being confident in something in the almost provable absence of any evidence. Feels more hygienic to reply "don't know" to this whole problem than to waste time trying to find an answer (as I'm hopelessly outmatched by the cursed nature of the problem).
Like, you might be convinced you possess ‘qualia’, and you might believe the same applies to me, or a dog, or a mouse… or a fish… but what about an ant? A plant? A bacterium? A neuron? A piece of semiconductor?
Somewhere along that continuum you probably say ‘yeah, there, that thing is experiencing qualia’. But why there? Why anywhere?