Originally Posted by Tavrobel
What one could deem by literary license, is that a Heartless is whenever one is split into its respective halves -- if you have a Nobody, then you are the Heartless. One could think that "Sora" played at the end of KHI and most of KHII, is a Heartless, but in Human form. The justification is that Ansem Darkseeker was also a true Heartless, but had a human form, and that Roxas does not fully reunite until Memory Skyscraper, which means that Final Form is Sora, as a whole, and fully wielding the power of the Keyblade as its Master should be. Anti-Form could also be used to justify that Sora cannot keep up the Charade longer, and he falls to the Dark thoughts within his mind, and unleashes power, unholy, and not with aid of the Keyblade. He also doesn't use recharging Orbs.
Of course the argument against the theory, is the exception of Kairi. She lost her Heart, but no Heartless formed, and also because she has no Darkness inside of her. This is untrue of Sora, who DOES have Darkness in him; he is no Princess of Heart.