Okay – now, let us apply Piaget's insights about how knowledge develops in successive layers not to thinking maturity, but rather to social maturity, a topic rather dear to the hearts of most people visiting this website, I expect. The questions to ask now are:
Are there successive layers of social maturity (e.g., appreciation of the social world and of emotions and how to manage them) that people experience as they develop?
If so, what are those successive layers of social maturity?
What sorts of problems arise when you get stuck in a particular stage of social maturity and fail to mature further?
These first two questions are addressed in "The Evolving Self", while the third question is addressed in Kegan's follow-up book, "In Over Our Heads".
What Kegan has to say in "The Evolving Self" can be summarized (I think) in this manner:
Social maturity does evolve or develop in successive layers just as does cognitive maturity, progressing from the most simple understanding to more and more complex understandings of the social world.
More simple appreciations of the social world, and of human emotions are fundamentally inaccurate, and not a good fit for the actual complexity of the social world, but they nevertheless represent the best people can do at any given moment.
More complex appreciations of the social world evolve into existence as a person becomes able to appreciate stuff abstractly that they used to appreciate only in concrete (obvious, tangible) forms. This is to say (using Kegan's terms) that people are initially embedded in their own subjective perspective. They see things only from their own particular point of view and fundamentally cannot understandwhat it might be like to see themselves from another perspective other than their own. Being unable to understand what you look like to someone else is the essence and definition of what it means to be subjective about yourself, for example. Being able to appreciate things from many different perspectives is the essence of what it means to be relatively objective.
New layers of social/emotional development occurs as people become able to finally see themselves in increasingly larger and wider social perspective. For example, the moment I am able to understand for the first time what another person is thinking or feeling, I have made a sort of leap forwards out of subjectivity (me being trapped in my own perspective) and into a view of the world that is a little more objective. If I can understand what someone else is thinking and feeling, I can also imagine myself as I must look through their eyes and my self-understanding becomes that much more objective. This sort of expanded awareness represents an emergence from embeddedness in my own subjective perspective and the growth of my ability to see things from multiple perspectives at once.
This process of becoming progressively less subjective as you mature, and thus more able to appreciate the complexity of the social world, repeats itself multiple times in a given lifespan (assuming people do continue to mature as they age and don't simply get stuck!). Each new layer of awareness; each expansion of perspective that a person grows is simultaneously both more objective; offering a better, wider perspective on the social world than did the prior understanding), and also less objective then the understanding that logically follows next.
Where does this progression end? Theoretically, it ends in some kind of Buddha-like state of enlightenment, where everything that can be understood objectively is understood objectively and there is no more subjectivity to be embedded in anymore. More practically, it ends when we reach the level of social maturity that most of our peers achieve. Few people ever become more socially mature than the majority of their peers.