"Why would I trust what you say, either?" he calmly retorts. It's not like Roxas calling something a soul has more merit than someone else's definition, if he doesn't know either side to be a trusted source. "You call something a soul, and they call something different a soul. Obviously, I'm going to need more details than that."

Memories, emotions, possibly personality traits? All of that information would be stored inside a human's brain, so it seems a bit redundant to him to give it a different name.

"Simulated emotions can be programmed, and memories are something that's acquired, so unless you have no long-term memory to speak of I wouldn't say it's impossible for you." Even if he's still not fully convinced Roxas is what he says he is, considering the circumstances... "Do you believe that there's a required level of emotional response for something to have a valid soul? If so, how would something like that be determined? Your responses are a bit stiff, but the other one seemed to react normally to emotional stimuli."

Add would know, since he's an expert at pushing people's buttons. An emotionless entity wouldn't get annoyed or upset so easily.