I think that there might be some questioning of terms here. I don't see Vito Corelone possessing "multiple personalities." Rather, I think that he is multi- faceted, in strong control of his emotions to the point where he knows what emotion is needed in which situation. Don Corelone is shown to be a very astute judge of character. While he is a mobster and is capable of intense violence, he also understands how to motivate people and how to "read" them to a point where they will be indebted to him. Part of what makes Santino, Fredo, and even Michael, incapable of being able to do what Don Corleone can do is because of their inability to control emotions as their father is able to do. Don Corelone can show great tenderness, for example in defense of his family, and can simultaneously show great intensity in anger and emotion, as in when he must act in their defense. Vito Corelone is shown to have experienced success in America because of the opportunities made available to him, but also because of his ability to understand people and understand how to work emotional attachment from them to his favor and to be in his debt. In analyzing this, I think that one is not really examining his "multiple personalities." I don't think Don Corleone is a type of schizophrenic who exhibits different personas without control. Rather, he is in full control of his emotional range and understands which emotion is appropriate in which situation, ensuring that all that he has worked for and towards will not be jeopardized by an emotional miscalculation.