Are you the same person today that you were yesterday? Or last week? Or last year? What about ten years ago? Let’s look at it in two ways: physically and mentally.
Physically, our bodies are constantly performing maintenance. Waste is being flushed away and the food that we eat is constantly being transformed into tissue, or used for energy. Over a few years (the exact number depends on who you ask) all of the atoms in your body (with the exception of some of your bone structure) are replaced. In other words, physically, you aren’t the person you were ten years ago. You may resemble that person from ten years ago. You may have many of the same memories. (Although probably not as many as you intuitively believe.) But all of the key physical parts have been replaced.
So what persists? What connects you to the you of ten years ago? (That is, aside from part of your bone structure.) The arrangement, the patterns, that make up you. We are information. Information that is at any one time are made up of the current matter in our bodies, but that, as the matter is cycled through, retains most of its structure. Most, but not all. For we are always aging. In youth, the pattern is still forming from the DNA, the blueprint in our cells, but as we age, the patterns loses more and more of its fidelity.
Ok, so what about mentally? Mentally (whatever we mean by that exactly), we’re the same person as ten years ago, right? Well, every experience we have alters us just a bit. (Of course, some experiences can alter us a lot.) Every new memory adds to our experience. We certainly are born with certain innate tendencies that are unique to us, but our experiences, our environment, also have a tremendous impact. If you are an adult, you are not the same person as the child you once were. An interesting exercise is to contemplate how the child you once were would react to the adult that you are today.
We are information, a wave of patterns that holds its shape despite matter constantly coming in and out. You could say that we are patterns of cells, and that would be accurate. Those cells are patterns of molecules, which are patterns of atoms. The atoms are patterns of subatomic particles such as electrons, protons, and neutrons. Protons and neutrons are combinations of quarks. According to the Standard Model of particle physics, we are patterns of elementary particles. According to string theory, we are patterns of one dimensional strings of energy. According to quantum field theory, we are patterns of waves or excitations of fields. The universe may be nothing but structure, patterns, all the ways down.
And we patterns have become aware, not only of our own existence, but of each other, the universe and nature, and our place in it, maybe.