Your definition of the soul doesn’t encompass its most common spiritual aspect, that being a “spark of life” which can exist independent of the physical body, and potentially transfer to a new body. Personally I don’t find your definition all that useful because we already have a word for that, sentience; and at a higher degree, sapience; which doesn’t come with the additional spiritual connotations of the soul. Asking “do animals have souls?” has a VERY different connotation from asking “are animals sentient?”; one is a spiritual question that has no right answer, the other is a scientific question whose answer is very much “no fucking shit” with the caveat that sentience is a sliding scale with no clear beginning point.
Are bacteria sentient? Almost certainly not. What about simple multicellular life like planarians? Small insects like ants? Large insects like rhinoceros beetles? Simple vertebrates like small lizards? Higher vertebrates like dogs, pigs, and dolphins? We can come up with subjective judgments in each of these cases but there isn’t really a clear line.
Personally, I believe that the “collective consciousness” is the thing that most resembles the classical spiritual definition of a “soul” - a form of higher-order emergent intelligence that arises from the interactions of lesser organisms, which is not bound to any one physical body in the same way that our own sapience is not bound to any individual cell in our brain. The classic example is the slime mold or the ant-hill or the bee hive: a super-organism comprised of many small component organisms that exhibits a kind of collective intelligence far beyond the capabilities of its individual components. I think that any kind of group or society will develop this collective consciousness once it reaches a sufficient scale or complexity, in an analogous manner to how individual organisms will gain sentience and then sapience as their complexity (or, rather, the complexity of their brains) grows.
So, is there in an immortal soul, more like. I disagree that experiencing qualia is the same as sentience, because you can't rule out the existence of a philosophical zombie (behaves exactly like a sentient creature but does not have subjective experience), I just don't think they would exist because there's no reason to assume that they would.
I feel like - and this is an idea that I sort of had as a revelation, but have been unable to formulate in a logical way - anything that experiences qualia has to have an immortal soul because qualia can only be experienced as a flow, and if that flow terminates at some point that ceases to be a flow. When I had general anesthesia for my wisdom teeth removal, it felt to me as close to nonexistence as I think any living person will ever achieve, because unlike the sensation of sleep or a coma, there was literally no experience of the passage of time, just an instantaneous jump from the last moment of lucidity to me coming back, and without any awareness before or after that it was ready to kick in. What I've read is that anesthesia like that operates by suppressing memory formation. The brain continues to experience everything it usually does, it is just as alive, but the memories don't form, so each sensation is just an instant in time, discrete, like a frame of video or a pixel in a screen. During that time I was definitely still alive and sentient, but while I may have in some physical sense been there, for any practical purpose I wasn't. There is something to that experience of memory, the flow of event into event, that makes life life. For it to stop would package it into a discrete event, disrupt the flow, invalidate the experience. I have a similar notion that the existence of multiple souls at the same time would require there to be some connection between them, sort of an implication of there being a single original soul off of which new souls emerge like branches off a tree, so there is a continuous stream of consciousness from the beginning of creation to the end, but these streams can still have gaps in them, the stream forks, and it only flows one way.
Your thoughts on collective consciousness pretty much meets mine. I believe that something like an ant - a thing that clearly goes about its world interacting with it intelligently - experiences some sort of internal life, yet the ants add up to form a single unit which demonstrates the properties of life (reproducing, structure, self-regulation, etc.) to the point where we call it a superorganism, acknowledge that it is for all purposes an organism unto itself, just one capable of dividing itself up physically. I think that human society demonstrates all of the properties of life and so is the direct equivalent of a clonal organism and (may) have its own crude sort of sentience. Similarly, given that I believe both individual ants and the anthill could have sentience, I don't see why individual cells of the body couldn't have their own internal life too. They resemble organisms inside and I assume (don't actually know anything about the evolution here) that multicellular organisms started out as unicellular superorganisms that just became incredibly complex.
