A person lives in as many worlds as important relations, and takes in each of them a specific identity. There is a private audience that makes us feel like home. With the recognition of oneself through the dynamic organization of shared reality. So, we are as many as significant and different "existences" we "act" on the realities we share.
Will Kant revolve on his coffin? Or will the majority of people simply say: "is this what you have to say? Give me a break! I know that since the first time I recognized my existence on the eyes of another."
Hum...True. Science comes always late. It's actions are always meta analysis, in a way that creates a discourse that explains plausibly what people are afraid or inhibited of saying.
So, what keeps us apart of a fragmented self? Simple: the coherent organization of difference and complexity.