Who am I, exactly? Who are you, exactly?

Times change, and so must I… we all change. When you think about it, we are all different people, all through our lives. And that’s okay, that’s good! You’ve gotta keep moving, so long as you remember all the people that you used to be.

-The 11th Doctor
The Time of The Doctor – Copyright 2013 BBC

Did you get misty-eyed watching that scene? I did, and I am not ashamed to admit it…

doctor 11 speech

Credit: BBC

Wonderful quote. I still get goosebumps every single time I re-watch the episode. It speaks to me at so many different levels!

Dr. Who is one of my favorite sci-fi shows ever, even though at a certain level, the “-fi” part of the show usually means that it invariably includes aliens and there is not a lot of “sci-” part either, because the putative science shown is usually so advanced that we would not even know how to begin to analyze and explain it in terms of plausibility. It is like how a typical 15th century person would see a cell phone: a rectangular “board” or thin “brick” made of a metal-like material, no more no less, yet capable of doing wonderful, “magical” things. Just like us and the technology portrayed in Dr. Who; a typical person in our time would not even know how to begin to analyze and explain it in terms of plausibility. Think about a sonic screwdriver for instance. To us, a sonic screwdriver looks just like a metal “stick” that is capable of doing really cool, quite “magical” things, yet we have not the **foggiest** idea of how it works…

I, of course, like the show of course in great part because of its “sciency” character, but it is so much more: Adventure, stories, and oftentimes poignant commentaries on the human condition.

Did you know that you and I are as old as The Doctor? This is absolutely true, at least in a strict physical sense. Some parts of us are older than others, though. The hydrogen atoms that we all have, and maybe some helium atoms that we just happened to inhale, are roughly 14 billion years old! As for the other heavier elements, they are not that old, but not by much; they are at least 4.6 billion years old, the approximate age of the solar system and most likely older. It is a well-established fact that several generations of stars need to happen to make elements heavier that H and He.

Of course, as I said, we are **really** “old” only in a purely physical sense. Your identity, what makes you, well, “YOU”, is a different thing. As far as we know, personal identity is a particular, rather special arrangement of atoms in time and space, especially the consciousness that emerges from this arrangement of atoms in a brain.

There is a problem, though.

This “particular arrangement of atoms in time and space” is anything but fixed, and this is true of Every.Single.Human.Being. And we are nothing special in this sense; this is also true of every other organism that shares the planet with us.

You see, life is anything but a static phenomenon. One of the best characterizations of the phenomenon of “life” that I have seen is found in the wonderful book “Weird Life”, by David Toomey. I really liked this book and I think you will like it too!

Anyway, Toomey compares the chemical processes of life to a juggler. Bear with me. If a juggler is **too** stable, as in frozen, there is no juggling at all. On the other hand, if a juggler is **too** unstable, things will fall apart really fast and there will be no juggling either. For a juggling act to be successful, it needs to be at a proper speed, not too slow, not too fast.

A similar thing must occur in a biological system. Molecules must be free to move, but no so free that this freedom would cause the system to decay, or in chemical parlance, reach “equilibrium”. As far as life is concerned, chemical equilibrium equals death.

Going back to the juggler analogy, imagine that every now and then, the oranges that the juggler is playing with are substituted by other oranges. It is the same juggler, it is the same process, but the actual, literal entities being juggled change over time.

This happens to us as well, our brains included.

It is “common knowledge” that every year, some 98 % of all the atoms in a human body are replaced. This was originally stated in a 1953 lecture on radioisotopes, as part as the Faraday Lecture Series by Dr. P.C. Aebersol (I am trying to trace earlier sources with hard data). This makes sense in light of what we discussed above, and it is part of the normal processes in metabolism and repair.

This means that in a completely real sense, the physical substrate of our brains, and by implication, what is most likely the physical substrate of our sense of “self”, changes over time. The baby, the boy, the teenager, the -several- adults that I have been over the years are literally no more…

This applies to you too… (:-/

Yet I feel like myself all the time and I hope that you do too. Nonetheless, I have changed over the years and just as The Doctor, I have been different people over time, with different ideas, different points of view, different priorities; but I have always been me, Oné.

This fact is like the apparent paradox that appears when you have a favorite car, which you never want to let go, but over the years, as parts decay you have other parts installed. Potentially, every single part can be replaced. When that happens, is it the same car?

I did not come up with that idea by myself. It is an ancient one posited by philosophers of old (Sorry NDT, but philosophy **is** useful!). One of the earliest written examples of this apparent problem was Plutarch’s “Ship of Theseus Paradox“, written in the first century, but it is almost certain that this is an older idea.

So, in an ‘oh-but-so-real’ sense, the bottom line is that we are essentially, information.

I, for one, even though I am a scientist, I am a rather cowardly one, as I feel thankful that we do not yet have the technological know-how to really test this idea.

For example:

**If and when we are able to download your consciousness into a computer: Who is the “real” you? (a similar concept is explored in the new Battlestar Galactica TV series when the Cylons download their consciousness into brand-new bodies…).

**If and when we are able to transport entities “Star Trek” style: If an accident occurs and two of you materialize, who is the “real” you? (Star Trek explored this possibility in the episode “Second Chances“).

**If and when we are able to time travel: What would you say to a 20 year younger version of yourself? (I would emphatically advise diet and exercise just to start with!).

See what I mean? I am sure that these ideas have been explored in more depth in hard science fiction stories…

The world of the mind is wonderful.

I think weird thoughts.


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  1. I had heard our cells are replaced, but did not know about our atoms. How does this work?
    If I could go back in time, I’d tell my 19 year old self to have more faith in her abilities. But then again if I did go back, and she accepted my advice, I wouldn’t be the “me” I am today. Not sure if this is a good or bad thing.


      1. Thanks for the link.
        As for your book, I think your writing style is great. Love your voice, but honesty, the worms creeped me out. I don’t wan to judge your book based on my aversion to flatworms. 🙂

        Liked by 1 person

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