Well, first and foremost, he does.
It's right there. Terranort states that his mind resists.
If you disagree with my definition of the mind, that's totally fine. But whatever the "mind" is, LS has it.
I guess my problem is that something that seems an awful lot like Terra's mind is seen talking to Master Xehanort in their combined heart. =/
Besides, is there any reason to believe that he's speaking in technical terms rather than in looser conversational terms?
The idea that Xemnas has the same mind as Terra is a pretty big leap.
Namine does not have the same mind as Kairi, Roxas does not have the same mind as Sora, Xehanort's Heartless does not have the same mind as Xemnas.
These are all cases in which two entities come from one being and yet operate under two separate minds. So while nothing is necessarily "replicated," something comes in to existence to give these beings their own unique identity. And it's not memories, particularly knowing that in Roxas and Namine's cases, they maintained their own identity without memories.
I was proposing that, in the case of Xemnas, he does have his own mind, separate from Terra and MX, but, given the memories he has and the vessel which influences his identity, he operates with the same motives as Terra.
You know what, you're right.
What I should have said is that, if the mind is something that's contained in the soul, Xemnas
ought to have it, since he's composed of Terra's body and soul.
Thinking about it a bit more, I'm kind of skeptical that the mind (identity/consciousness?) is something that exists in KH in the same literal sense that the body/heart/soul do. It seems more like it would be something that arises from one or more of the others, with memories being at the very least a huge influence. (Does Organization Roxas have the same mind as Twilight Town Roxas? He's certainly a very different person) I don't know how it could exist separately from those other elements when it's so interconnected.
I mean, all of the cases of two entities that come from one being but have separate "minds" involve two entities with different memories. Namine is not Kairi, because she has had different experiences. Roxas is not Sora, because they have had different experiences. Xemnas is not Xehanort's Heartless because... well, in that case, it's because Xehanort's Heartless is a Heartless - Xemnas certainly seems to consider himself to have the same mind as Apprentice Xehanort, if his conversation with Ansem the Wise is anything to go by.
...none of which, I think, would really affect your theory all that much. It'd just explain where the "new mind" came from.