Did you ever revisit your childhood home and get hit by a smell you had forgotten, suddenly transported to a worldview from long ago?

Which version of you shows up at your high school class reunion?

Do you find a different side of yourself emerges each time you speak with your mother, father, or older sibling?

I think I am pointing at a well-established dynamic: we are not one solid person. We may appear to be so on the outside and may think we’re supposed to be on the inside, but just change our scenery and witness how a different side of ourselves emerges. With all these different selves appearing, we have to ask: what unifies them all?

When I work with people in my office, I keep a matryoshka doll, sometimes called a "Russian nesting doll," in my desk drawer. I’ll take it out and take it apart to illustrate what human development is really like. We don’t march in a straight, linear line from one version of ourselves to another, the latest version erasing the ones that came before. We’re more like these Russian nesting dolls, where later versions are larger and more complete versions of our earlier selves, and they incorporate those prior versions within them. But those younger versions, like the smaller nesting dolls, have their own separate life and can emerge whole if the outer circumstances open up enough to allow them out.

This is how I explain what happens when suddenly we act like much younger versions of ourselves, oftentimes to our own frustration or consternation. When you go to your high school reunion and you immediately become that insecure teen you were 25 or 40 years ago; when your 90-year-old father raises his eyebrow in a way he did when you were a child and you immediately snap into line; when you meet a former lover from decades ago and you suddenly feel young and alive again in a way you first did when you were with them—all of these are examples of your earlier selves, perhaps dormant within you, coming back to life and showing up in the outer world.

Walt Whitman, in his poem “Song of Myself,” said, “I contain multitudes.” So do all of us, and I think the more we can recognize and make space for the existence of these younger versions of ourselves, the more we can cooperate with their appearances in our lives. They are not something to be ashamed of or embarrassed by but rather important vestiges of our personal history we can meet and appreciate when they appear.

As for what unifies all these versions of our multitudes, to me, the answer is simple: it is the non-material truth of who we are, that version of ourselves that remains unchanging no matter our age or our external circumstances. You can call it whatever you like: atman, the Higher Self, psyche. I call it the soul.