Many times in real life, four words of a person are placed together.
Heart, Mind, Body and Soul.
Now, three of these four things have already been used. The Heartless are the heart, and the Nobodys are the Body and Soul. Which leaves the Mind left behind. And knowing Nomura, he doesn't leave one thing unexplained.
If you think about it, the mind controls every other part of the body, and that remains constant even in a video game. Even in Kigndom hearts, it's the mind that plays the main part in keeping someone alive (Though, if the Heart is removed, then they are automatically gone.) Look at the case with Lingering Sentiment (LS). Terra's armor was simply nothing when MX took over. However, Terra became LS. And, you need a mind to work a body. Hence, the LS had to have some kind of mind to be able to fight, move, speak, or anything such as that.
With Vanitas Sentiment, Vanitas was defeated and returned to Ven. However, Ven then went into a comatose state, and placed in the Room of Awakening. From there, his heart went back to Sora, where they connected. With Vanitas still in Ven's heart, those moments would have given him a chance to escape, back to where he was defeated. However, being that he no longer possessed all four things that create a person, he could not be whole. He had a mind, and he had a heart. However, his body and soul no longer existed. Being that the Mind and Heart are both connected to someone's memories, that could be why Vanitas appears as he does, and no longer with his mask removed. He isn't what he was when he was defeated, only the memory of one.
Therefor, the Sentiments are simply memories of the old self. LS is a memory of Terra himself fighting in it, and Vanitas is a memory of the being he once was. The memories allowed them to have minds, and thus, allowed them to be a half being, in a way
Heart, Mind, Body and Soul.
Now, three of these four things have already been used. The Heartless are the heart, and the Nobodys are the Body and Soul. Which leaves the Mind left behind. And knowing Nomura, he doesn't leave one thing unexplained.
If you think about it, the mind controls every other part of the body, and that remains constant even in a video game. Even in Kigndom hearts, it's the mind that plays the main part in keeping someone alive (Though, if the Heart is removed, then they are automatically gone.) Look at the case with Lingering Sentiment (LS). Terra's armor was simply nothing when MX took over. However, Terra became LS. And, you need a mind to work a body. Hence, the LS had to have some kind of mind to be able to fight, move, speak, or anything such as that.
With Vanitas Sentiment, Vanitas was defeated and returned to Ven. However, Ven then went into a comatose state, and placed in the Room of Awakening. From there, his heart went back to Sora, where they connected. With Vanitas still in Ven's heart, those moments would have given him a chance to escape, back to where he was defeated. However, being that he no longer possessed all four things that create a person, he could not be whole. He had a mind, and he had a heart. However, his body and soul no longer existed. Being that the Mind and Heart are both connected to someone's memories, that could be why Vanitas appears as he does, and no longer with his mask removed. He isn't what he was when he was defeated, only the memory of one.
Therefor, the Sentiments are simply memories of the old self. LS is a memory of Terra himself fighting in it, and Vanitas is a memory of the being he once was. The memories allowed them to have minds, and thus, allowed them to be a half being, in a way