R. D. Laing says in one sentence what has taken me thousands of words:
“our relatedness to others is an essential part of our being … but any particular person is not a necessary part of our being” (Laing 2010: 26)
This is what the (confusing?) diagram from my PhD is intended to illustrate. Any person’s biography is intertwined, at many points, with the biographies of others. I’ve always liked symbolic interactionism* because it so insightfully analyses the T2-T3. Whereas I want to understand the whole process:
- Our relatedness is essential to our being: ‘I’ am always in some relation to ‘We’.
- But the ‘I’ and ‘We’ change: no particular person is an essential part of our being.
If you accept the underlying premise (many wouldn’t) then the problem you’re left with is fascinating.
Mark Carrigan 
I think what Christian Smith (2010, p.338) writes is relevant here: “Since fundamental life meanings are rarely fixed and indubitable, our “ontological security” – that is, our basic sense of mental stability and trust that the natural and social worlds, including self and identity, exhibit continuity and are what they appear to be – remains vulnerable to the threats of destabilization and disintegration…So every person’s ontological security is susceptible to undoing. And that sustains a particular precariousness in the human existential condition”.