You know more than your past self knew. Your future self will have more experiences than your current self. Is that enough to make them different people?
Occasionally, it can be helpful to consider your future self a different person from your present self.
“That’s not my problem,” you might think to yourself. “That’s my future self’s problem.”
Similarly, if there is one person you can be sure that you are smarter than, it is you from the past. You have all the knowledge and experience that that person had, plus whatever you have learned or experienced since then.
But is that enough to define a different person?
Obviously, your past self, present self, and future self have some commonalities. The decisions that your past self made led to the current you, and what you do now will set the stage for who you will become.
In addition, you all share the same DNA, have the same parents, went to the same high school, and so on. You share a temporal existence.
However, your body, and everything around you, is constantly in flux. Each breath you take is slightly different in composition, the food you eat from meal to meal varies, your microbiome is always changing, and so on.
As the saying goes, you can never step in the same river twice — all the water changes from moment to moment, as it rushes downstream and is replaced with the water coming after.
Is it the same with your body? As cells live, divide, and die, to be replaced by new cells, are you the same when most, or all, of your cells are replaced?
When you think about the person you used to be, or the person you will become, do you consider that a different person? Or are they all just you, with some minor tweaks and changes?
Related questions: What advice would you give your past self? Past, present, or future? How much does your past determine your future? What do we owe the future? How do you plan for the future?
I agree with the line in this question: You can never step into the same river twice. While I share experiences with the person I was before, I am markedly different, with incredibly changed life choices ahead of me. The following are a couple of examples to illustrate this.
First, I grew up poor. Even though I was a tween and teen during this period, I felt the stressors of the daily struggles my parents had to deal with to keep making ends meet or live with the consequences when that was not possible. Because of my economic situation (and not having any family members who had pursued higher education), I had only learned that college was possible when my high school guidance counselor demanded I apply to several colleges/universities I would like to attend — I had come to her with job goals she knew I could exceed. Because my guidance counselor pushed me, I now live a financially secure life (knock on wood). The options I have are much more expansive than what was possible during my teen years.
Second, I had a profound experience that happened to me nearly twenty years ago that I’ll keep to myself. After experiencing it, it felt like a switch had been flipped, and my motivation for living life had changed from being angry at what I knew was wrong with the world to aspiring for the hopes I had and knew were possible. In fact, I worried that I might be unable to continue advocating for social change because I was a different person. Luckily, I found ways to bring my joy for what was possible to my vocation.
I live a different life than when I was younger. I suspect the same for my future. I am and will be a different person.