You asked, “How does the self learn to relate to the world?” But actually the self starts by dividing itself off from the world. Some parts, some sources, of stimulation are always here, others are not. That difference is one basis or beginning of selfhood. Then we elaborate it more, adding a social identity and relationships, and other things.
— Roy Baumeister, Quid pro quo: the ecology of the self
Why in fact is there just one of you instead of a probability smear across a hive mind of some kind? The understanding of personal identity has been a puzzle for centuries. To grasp all that identity means now, we need to know what personal identity is at its core. Identity has continuity, cohesion and uniqueness, but each of these qualities can be somewhat hard to pin down.
All the evidence is that our minds consist of many interacting pieces, many of which are not even conscious. Nevertheless, the vast majority of us feel like, and present as, a single cohesive person, continuing over a lifetime. Much scientific and philosophical effort has been spent of late on the nature of the self and its conscious mind. It turns out that there is no single explanation for what holds you together. Instead, it is a coordinated meshing of multiple levels of reality: physical, personal, and social.
The physical level starts with DNA, but it’s really about how biological processes create encompassing boundaries within which are built the foundations of our uniqueness: a cellular structure, a nervous system and an immune system. We think that the physical body continues through our lifetime. In fact our component matter and structure changes continually, so that there is not really any specific physical thing we can claim to be us throughout life. Furthermore, quantum theory doesn’t even allow that any one of your atoms is the same from time to time. There essentially is no “same” to an atom. The prevailing theory, then, is that what persists physically is a pattern, not specific matter.
But there’s another level. Using our physical framework we develop a mental one. This is the reality interpreter called the Self. Thereby, we know things. The peculiar aspect of the human Self is that we self reflect. We know that we know. That Self intuitively believes in its own continuity over time but, like in the physical case, change is continual in the mind. This leads to interruptions and paradoxes that belie the continuity that we imagine ourselves to have.
What’s left to (finally!) hold us together? It’s our social environment. It’s our roles, our relationships, our tribes and institutions. We are the same person as last month because others who know us say that we are. We are the same person as an infant decades ago because our family knows it to be true. Our culture gives us an identity even before we are born, and it preserves it in some important ways even after death.
Throughout life these three levels of reality mesh to hold us together. The result is not only continuity, but uniqueness among our fellow humans. That uniqueness, as opposed to our place within family and society, is becoming more and more a focus of our conscious Selves. In the second decade of the 21st century, our “true self” has devolved into a personal brand, an attention-seeking marketing missile aimed at other people. It’s getting a little frenetic.