Can't tackle the whole explanation right now, but to clarify a point:
Not really. He makes it sound like a completely different, separate part from the body, states that it can't be solidly defined, and calls it a soul once.
Also, I never said it was exactly like a soul, just that it was starting to sound like one. And souls...bug me. They're the cheap way out of this kind of discussion.
I thought he was saying the point in which it stops being a part of the mother and starts being an individual entity cannot be solidly defined.
Yes. That specific line is the single most important part of this whole thing.
It's not that it "cannot be defined", it's that it "isn't defined". There's a subtle difference, because this transitory period has similar implications to... that darn boat I still can't remember the name of. What happens is a gradual transition from an "organ" to an "entity", and you can only say with certainty that it stops being an "organ" once it stops being connected - up until that point, the physical connection ensures that the mother's chemistry still affects the baby. There is no one specific point - even organs have their own basic reactions to stimuli, and produce their own patterns, even if their energy levels are weak. Without a certain defined threshold, there is no way to tell when it stops being one and becomes the other until it stops qualifying for one of those things altogether.
For instance, take wind. At which point does a "breeze" become a "wind"? At which point does a mere wind become a gale? Without specific numeric definitions for wind speed, you wouldn't be able to tell, except by using your own judgement. But you can probably agree that no matter the speed of the wind, once it starts forming a vortex, it's some form of a "twister" - because the defining trait of a twister is the vortex, and until it loses that vortex, it remains some form of a twister - call it a tornado, a "smerch", anything. Wind going in a straight line is some kind of wind. Wind deciding to breakdance is a twister. Same with being an "organ" and a "baby" during birth - and you're welcome for the mental image of someone breaking wind in such a way that it forms a twister. The bottom line is that the transition point
isn't defined - it can be debated back and forth, it can be set arbitrary cutoff limits for, say, pattern randomness and intensity (good luck doing that to things that can't currently be meaningfully measured), but ultimately it's a smooth transition from one to another with only a definite startpoint and endpoint to the process, and no defined point inbetween where one definitely becomes another.
Linking that back to "souls" - an "imprint" in my definition encompasses the same things that are normally filed under "soul", but it's not limited to that. It's something of a mechanical explanation of the concept of a soul, of consciousness and identity - "mutually interfering systems" is a good way to put it. The identity - the mind - is changed over time as it responds to stimuli, which it receives through the body via the many ways the body works and interacts with the world. The "imprint" is... uh, crap. Hit the barrier again. It's... basically a "wake" left by the energy patterns of the body, but not a "disturbed" kind of wake, and it's not an "imprint" like you'd expect from the term - it's... back to cellular automata again, imagine a cellular automata pattern that... leaves order in its wake when going through chaotic inputs. Like you have a typical screenful of dots just roiling around quasi-randomly, and then you add in a pattern that acts like ice-nine, expanding through the chaos from a single point and leaving stable patterns in its wake. That's kind of like what I'm talking about. And this "imprint" is permanent and unique to the person, thanks to unique stimuli that the person experiences, however it's not necessarily unique to the person
entirely. Two people in similar states of mind walking down the same empty street at the same time of day experience very similar stimuli, and form very similar patterns in their "imprint". It doesn't cause them to hear each other's thoughts, not unless they're
very similar people with similar histories and mindsets, but just that part that overlaps may influence them. Unknowingly, a person may "walk into" another person's "wake" and inadvertently respond to stimuli that the other person was experiencing.
And that adds another layer to the mutually interfering systems, as different people with similar patterns influence each other. A mother teaching her child gives the child knowledge, but she acts through the body - she provides stimuli, be it visual or aural, and it's the child's body that reacts to those stimuli, and its "mind" reacts to the changes in electric impulses of the brain, changing gradually. But the mother's "love" is another thing - it's a complex interaction that forms a feedback loop with the child, as the child's patterns are constantly linked to the mother's, not least because a lot of them are shared due to the interactions during pregnancy. This feedback loop affects the child and the mother both, and changes in the "imprint" of one can induce changes in the "imprint" of the other. They are still different "people", but they share some parts - returning to the OS analogy, it's similar to cloud storage and computing - different OS instances can be using the same files, and even some of the same CPU cycles to run, yet they are still fundamentally different instances run by different users. Cases of split personality then are like multi-user setups on a single machine... the analogy can go on.
It's very hard trying to explain things like this without proper vocabulary. I keep suppressing urges to refer to the Matrix and quantum mechanics, among other things, because while they would help see the picture better, they would not at all add verisimilitude to my explanations, and verisimilitude is pretty much the only thing this explanation runs on, lacking any other means to verify and support it.