RWDevCon Inspiration Talk – Identity by Alexis Gallagher

Alexis shares his thoughts on identity, taking ideas from moral philosopy and programming and examining them through the lens of his own experiences. By Alexis Gallagher.

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Note from Ray: At our recent RWDevCon tutorial conference, in addition to hands-on tutorials, we also had a number of “inspiration talks” – non-technical talks with the goal of giving you a new idea, some battle-won advice, and leaving you excited and energized.

We recorded these talks so that you can enjoy them, even if you didn’t get to attend the conference. Here’s our next talk – Identity by Alexis Gallagher – I hope you enjoy!


“I enter the teletransporter. I’ve been to Mars before, but only by the old method: a spaceship journey taking several weeks. This machine will send me at the speed of light. I merely need to push the green button.”


“Like others, I’m nervous. Will it work? I remind myself what I have been told to expect. When I push the button, the scanner here on Earth will destroy my brain and body while exactly recording the state of all my cells. It will transmit this information by radio.”

“Traveling at the speed of light, the message will take about an hour to reach Mars where the replicator will create out of new matter, a brain and body exactly like mine. It’s in this body that I will awake.”

“I believe this is what will happen, but still I hesitate, but then I remember my wife grinning this morning when I confessed to her my hesitation about it. She reminded me she has often been teletransported, and there is nothing wrong with her.”

“I press the green button. As predicted, I lose consciousness and seem a moment later to regain consciousness, but in a different cubicle. Examining my body, I can find no change at all. Even the cut on my upper lip where I was shaving this morning is still the same.” (Taken from Reasons and Persons by Derek Parfit.)

Hi, I’m Alexis. I haven’t actually been to a teletransporter, but I think it’s a really interesting to discuss a parallel that I noticed. In this talk, I want to tell you about that parallel, and then I also wanted to offer what’s really a personal reflection on it.

Some of this is a bit philosophical. Some of it is a bit personal. I hope some part of it speaks to you.

Derek Parfit Defines The Transporter Problem

Derek Parfit wrote the passage I just read, which begins a discussion of the transporter problem. He wrote this in a book called Reasons and Persons in a chapter called “What We Believe Ourselves To Be.”



Parfit worked on that book for 15 years, and when it came out, everyone loved it. Philosophers have said that it’s the most significant work in moral philosophy since 1837.

I first heard Parfit lecturing about 20 years ago, and in-person he has exactly the sort of unworldly air you would expect from a legendary moral philosopher. He has dramatic white hair. You could say he’s sort of an alpha nerd in the world of moral philosophy.

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The transporter problem is intended to clarify ideas about personal identity. Remember, the transporter consists of a scanner and a replicator. The scanner destroys your brain and body, turning it all into information. Basically, it’s like NSCoding, but for your body.

The question is, how do you feel about NSCoding for your body? When you walk into the transporter, do you hesitate before you push the green button, or is that something you are happy to do?

Do you feel like the transporter is killing you and creating a new person, or do you feel a transporter is just moving you by moving your body? Is it the same you coming out of the transporter?

Defining Terms To Help Us Understand The Problem

That comes down to what makes two persons the same person. To consider this, Parfit distinguishes between two ways that any two things can be the same.

One way things can be the same is if they are qualitatively identical. This is a piece of jargon from analytical philosophy. This just means that things are exactly alike. They are alike in their observable qualities.

  • One example would be mass production. If I have a factory making ping pong balls, and two ping pong balls come out, they are going to be qualitatively identical.
  • Another example is identical twins. If two identical twins are atom for atom or cell for cell identical with each other, you could say they are qualitatively identical, but that doesn’t make them the same person. Fred Weasley is not the same person as George Weasley, even if they look exactly the same, even if they are physically the same.

There’s a sense in which they are identical, qualitatively identical, but there’s another sense in which they are not. That other sense is called numerically identical. We say two things are numerically identical if they are actually one and the same thing.

  • Imagine your factory with mass production of ping pong balls. It’s spitting out 100 a minute. If you looked at one of them and just followed it with your finger to keep track of it, you always know that one is the same as itself.
  • Another example, thinking again of twins, you are always the same as yourself through time. One thing is always the same as itself. Fred Weasley at 10 is the same as Fred Weasley at 20. It’s the same entity.

This idea, with this distinction in-hand, we can restate the transporter problem. Remember, by definition, the transporter preserves the exact state of all your cells. By definition, the person leaving the transporter is qualitatively identical to you. That’s what the transporter does.

That leaves the big question. The big question is, is it the same person walking out? Is that person numerically identical to you?

Am I The Same Me?

That’s really a question about what kind of thing a person is. From inside, I feel like it’s the same me through time.

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I feel like it’s the same me who is trying to pick up the pumpkin. It’s the same me who was in college with an umbrella indoors for some reason. I feel like it’s the same me as the me right now, that all of these are the same entity.

That’s the feeling, but what makes that feeling true? Is it just about physical continuity through time, like the same criterion that you would apply to a rock, or is it continuity of my memories? This is what John Locke believed, that what makes us the same person through time is you can form a chain of memories going back all the way to as soon as you started having memories.

Parfit considers many theories. I’m not going to review them all here. I just want to get to showing you the parallel that I promised.