To paraphrase Chonsky (link below), the legacy of Descartes' observations for "mechanical philosophy" is profound: substance-dualism became untenable because no coherent idea of material can be formulated. Newton exorcised the machine (material), leaving the ghost intact to be curious about itself.
Today we study the organism called the body without need of a philosophical grounding in any reality. "mechanical philosophy" ended with Newton's work obviating any coherent notion of an "intelligible world". Faced with unreconcilable confusion about what constitutes reality, science quietly abandoned the idea and moved ahead with "intelligible theories about the world", which Chomsky regards as one of most significant shifts in science.
https://m.youtube.com/watch?v=bWDJ2zFe4Pc
In various speeches and lectures on the history of science and linguistics, Chomsky comments on artificial intelligence, by referring to Alan Turing's seminal paper, in which Turing proposed the so-called "test." Chomsky refers to the paper's first paragraph where Turing concedes that the meaning of the word "intelligence" is so indistinct as to be left to be determined by Gallop. Turing punts on the entire question of the meaning of intelligence by suggesting an "imitation game."
Today's state of the art of machine intelligence has not advanced past Turing's proposal. Chomsky wonders if we may have to resign ourselves to the limit that it never will, in which light of reason we might embark on further study of ourselves, rather than contrive facsimiles and endure all the attendant hazards.
I think it's an incoherent concept. If the 'soul' is anything, there is some difference in the brain that would allow it. You can't have two people with identical brains and claim that one has a soul, unless you believe in magic.
To maintain that belief you have to either believe there is a physical source of consciousness, or that consciousness doesn't exist, neither of which most people can accept, yet LLMs are forcing people to confront.
The problem is that subjective experiences don't fit well with objective explanations. Nagal laid this out in his paper, "What it's like to be a bat", and other philosophers like Chalmers expanded on it with p-zombies and blind color scientists.
The only reason "avoid dangerous things like snakes so I continue to live" is a goal is emotions.
Emotions do not only exist in the not actually a real thing system 1. People who take damage to the emotional centers of their brains become passive and apathetic not hyper intelligent system 2 Vulcans.
Something that predicts no observable differences is unfalsifiable aka bullshit.
From there I think "we don't know how" is in part down to needing advances in neuroscience, and in part down to "consciousness" being a hazy term with disagreement over definition. But for frameworks that accept the above (physicalism, interactionist dualism, ...) I do think it's in theory testable whether something is conscious for any given pinned-down definition (e.g, "are the neurons constituting internal train of thought firing"), and I would be inclined to say the frameworks that don't accept the above are indeed the more "bullshit" ones.
I don't mean it necessarily has to be scientifically analyzable with current technology, but it must have some impact on the physical world (even if indirect) - else it cannot be what we're referring to.