Sorry to hear you found my little theory complicated, Alley. Not to worry I think I can clarify it.
You ask me what my definition of mind and soul is. I have to answer it doesn't matter. I can only use explanations found in the Buffyverse, because that's what we're talking about.
You ask me how I know there is a difference between mind and soul in the Buffyverse, and if so how do I know what it is. Simple--they tell us.
Personally I thought I explained that clearly when I said
The mind can act independently of the soul. In the Buffyverse a vampire is mind and body, but no soul.
You seem to suggest more detail is required. No problem let's get into it.
Let's consider Angel and Angelus; two distinct personalities, both sharing the same body, knowledge and memories of experiences. What separates the two and makes them each a distinct personality? Angel has a soul. In the Buffyverse a soul is a noticeable physical entity. In the Angel 4 episode Opheus we see the soul glowing in the Muo-Ping (the jar). When willow breaks the jar, we see the soul physically escape. I don't know how much more proof you would need to convince you the soul exists as a separate entity in the Buffyverse.
So the soul exists, but what is it? What does Buffy mean when she says of Spike, "He's different. He has a soul now."? She means he has a conscience; a knowledge of right and wrong with an inborn preference to the latter, and guilt when that preference is ignored. Guilt is what forces Angel into the Alleys to live off the blood of rats, after he feeds from the dead soda-jerk in Orpheus. He feels guilty because he believes he did wrong. Angelus who tells us he experienced the exact same event has no guilt concerning it. Why not? He doesn't have a soul and therefore no conscience. In the Buffyverse the only thing we know about the nature of a soul is it is connected to conscience.
So how can we postulate the separate entity of a mind based on what the Buffyverse tells us? When Buffy comes back from the dead in Season 6, she comes back with all the knowledge she acquired in her life. She interacts with this knowledge in a manner that is distinctly Buffy. This knowledge and behaviour has existence in the Buffyverse. It requires a name. The Buffyverse does not choose to give it one, but if I choose to call it "the mind", I don't think it's too much of a stretch. I think I'm still playing within the rules. I've only given a name to something that exists within the Buffyverse.
Angel and Angelus share the same memories, but they interact upon them differently. They have two separate minds, this is why Angelus refers to Angel as "him", and not "me". They have different "minds".
At this point I'm going to suggest to you it's shown quite clearly the mind and the soul exist in the Buffyverse as separate entities. So let's get back to what we we're really talking about: This Year's Girl.
You tell me I say
It was the interaction of Buffy's enlightened soul with Faith's mind that rebooted the knowledge of right and wrong.
Actually I don't. I only say it's possible to make an arguement for that theory.
You're arguement against that theory is
If so, Buffy's mind should have been poisoned by Faith's soul
Why? Buffy's mind is stronger than Faith's. It has met and defeated the urge to evil before in When She Was Bad. Goodness is engrained in the mind of Buffy.
So in this years girl, the souls were switched.
No. Based on what the writer's give us, we can only conclude the mind's were switched. The soul's may also have been, but we are given no evidence to conclusively prove it.
Can we conclude from this that Faith (in Buffy's body) didn't have her own memory, she didn't know what she had been thinking in season 3, why she had done what she had done
Huh? Where did you get that idea? Faith remembers the mayor? The only Scooby she doesn't remember is Anya. She'd never met her. I don't understand what you're saying.
Strange, they never told us that!
Never told us what? I don't have a clue what you're talking about. I don't know. Maybe it's too complicated for me. Try to explain it again more clearly.