The Mind-Bending Paradox You Haven’t Heard Of

What actually makes you you? Today I’m going to present to you a mindbending thought experiment about what it means to be you that I promise you’ve never heard before because I created it. I call it the brain of thesis. It builds on ideas from 17th century philosopher Thomas Hobbes as well as the modern philosopher of mind David Chomers. The answer to this puzzle says a lot about what it means to be a separate person. Imagine that it’s the far future and

That surgical technology, 3D printing of electronics, and our understanding of the brain are far more advanced than they are today. You volunteered for a very unusual experiment. Each evening, you’re put under anesthesia by a surgeon. The surgeon then one scans a tiny piece of your brain. two, uses an advanced 3D printer to create an extremely accurate electronic replica of that tiny piece of your brain designed to perform exactly the same function. And three, carries out a surgery to

Replace that original tiny piece of your brain with the electronic replica, carefully preserving the original piece of the brain on the side. You’re then woken up since only a tiny piece of your brain was removed. And because it was swapped with an electronic piece designed to perform exactly the same function, you notice nothing different about yourself. You still have the same personality, same memories, and the same behaviors. All that happened was a tiny bit of your brain was removed and

Swapped with a functionally identical piece of electronics, but you’re still obviously you. The next evening, the entire process is repeated again. Another tiny piece of your brain that had not yet been replaced is scanned. An electronic replica is made. And that tiny piece of your brain is swapped for the electronic replica. You wake up again, and again, you have the same memories, personality, and behaviors. The whole process repeats night after night, swapping just one single piece of

Your brain each night for an electronic equivalent until 50% of your brain has been replaced. Before I reveal the twist to this thought experiment, take a moment now to consider, is that person in your body still you at that point once 50% of the brain has been swapped, remember even though 50% of your brain has been swapped, you still have the same personality. And furthermore, each bit was swapped a tiny piece at a time. After no swap, did you feel like a

Different person? Many people would say that the person in that body is still you. Well, now it’s time for the twist. It turns out that surgeon was actually lying to you about what was happening. What you thought was that each evening the surgeon was scanning a tiny portion of your brain, then using a high-tech 3D printer to print an electronic version of that portion of your brain that does the same thing. But the actual truth was

That on the very first evening, the surgeon scanned your entire brain and made an electronic replica of the whole thing. And he kept this electronic version running in his lab. This electronic replica, though it didn’t have a body, was just like your real brain. When it runs each day, it is all of your memories and personality. It even remembers going to sleep on the first night of the surgery, just like you do. However, every day when the

Electronic replica runs in the surgeon’s lab, it’s simply a brain in a vat with no body. So, it has the thoughts that you would have if you found yourself as a brain in a vat. Okay. But what was the surgeon doing during the surgeries after the first night? Well, the surgeon really did swap out a tiny portion of your brain with an electronic equivalent part, just like you’ve been told. But it turns out he wasn’t creating a new tiny

Electronic replica of each corresponding portion of your brain. Instead, he was simply swapping that tiny portion of your real brain with the equivalent portion from the replica. Just as your real brain was having a small electronic part swapped into it each evening, the replica brain was having a small flesh part from your original brain swapped into it. So, your real brain was becoming increasingly electronic night after night, while the electronic replica was becoming increasingly flesh night after night. Now that we know what

The surgeon was really doing, let’s revisit the question that we asked before. What happens after 50% of your brain has been replaced with electronic parts? Before we said that the brain in the original body has still got to be you because each night only a small part of the brain is swapped and after each swap you’re still effectively the same. But now we know in fact that a full replica of your brain had existed all along. So the situation is more

Complicated. Yes, your original brain only changed a tiny bit each night, eventually ending up 50% electronic and 50% flesh. But that also means that your electronic brain was becoming a tiny bit more flesh each night. Once 50% of the brain in your body has been swapped for mechanical parts, are you still convinced that the brain in your body is you? Or could it be that the actual you is the brain in the vat? Before I reveal

The final twist, take a moment now to consider which of the two brains is really you at this point. Once 50% of the brain in your body has been swapped for mechanical parts, are you still convinced that the brain in your body is you? Or could it be that the actual you is the brain in the vat? Time for the final twist. The surgeon isn’t satisfied once he’s replaced 50% of your original brain. He continues with the procedure

Night after night, doing the same thing as before. Every evening, he continues to swap a tiny remaining flesh bit of your original brain with an equivalent electronic part of the brain in the vat. After many evenings, the procedure is finally complete. The brain in your original body is now 100% electronic. But that also means that the brain in the vat is now 100% flesh. Not only that, but the brain the vat simply just is your original brain. If we just focus

On what happened each night, we recall that a small part of your original flesh brain got swapped with a small part of the replica. But if we take a bird’s eye view of what happened overall, all that occurred is that your original flesh brain was taken out of your body piece by piece and completely reassembled into an essentially identical flesh brain sitting in a vat. Meanwhile, the electronic replica of your brain was also taken apart piece by piece and

Completely reassembled into your original body. So that leaves us with a very challenging question at the end of this entire process. Which one is you? Are you the flesh brain that is sitting in the vat at the end or are you the electronic brain that’s inside the head of the original body? It can be hard to make sense of the question, which one is really you? So I’ll give you a different, more concrete way to think

About this question. Suppose you knew all of the details about how the procedure was going to be carried out. Furthermore, the surgeon, who at this point we can safely say is completely insane, gave you a choice. He says that after the entire process is complete, he’s going to torture one of the two brains. But he’s going to let you, prior to procedures taking place, decide which of the two brains get tortured. The question then is, if you’re acting

Purely selfishly, which brain do you choose to have tortured? Do you choose to have him torture the fully fleshed brain that ends up in the vat at the very end? Or do you choose to have him torture the fully electronic brain that ends up in the head of your original body at the end? If you thought you’d end up as the flesh brain in the vat, you choose to have him torture the electronic brain at the end. On the

Other hand, if you thought you’d end up as the electronic brain, you choose to have him torture the flesh brain that ends up in the vat. Let’s consider some possible solutions to this problem. After that, I’ll tell you what answer the famous philosopher David Chomers told me he believes is correct. Possibility one, we could say that the brain and the body started out as you and then at some discreet point things flipped so that you end up in the VAD

Instead. But what seems to make no sense about that is where to draw the line on that flip. For this to be true, then one tiny part of your original brain being moved from your head to the vat would have had to change which one is really you. Possibility two, we could say that at the end, neither of the two brains is you anymore. This seems pretty weird, though, since after each small surgery, it seems nearly certain that the brain

In your body is you in a meaningful sense. Each surgery changes the brain only a tiny amount and preserves your personality behaviors. How could you still be fully you after each small surgery and yet at the end neither brain ends up being you? Possibility three, we could say that both brains are equally much you. That is, there are actually two U’s at the end of the experiment. This also seems weird, however, because it’s unclear at which point you started

Splitting to two. This also seems weird because the brain and the vat ends up being made of all of your brain material. So, how is it possible that we moved all of your brain material into the brain the vat and yet you ended up split between the two? Possibility four, we could say that this thought experiment is physically impossible. That is, it’s somehow prevented by the laws of physics. While it’s true that no technology like this exists today, and

It’s also likely true that no perfect electronic replica of the brain could be created, it isn’t clear what law of physics would prevent something very similar from the scenario from actually happening. Possibility five, you’re still the brain in the body. Even though that brain is electronic, you stay in the body fully and determinately with every small exchange. So, you stay in the body after the full exchange process is completed. Possibility six, we are so deeply confused about identity that when

We say it is or isn’t you, we don’t realize that what we are saying is actually not a sensible or meaningful question. Possibility seven, we could say that you started out in the body, but then for a while you were mingled with this other electronic copy, but by the end you separated out again with you ending up in the vat. After all, if someone cut up your brain and then used advanced technology to reassemble it just the way it was, wouldn’t the

Reassembled copy still just be you? Take a moment to think about which of these seven possibilities you think is the answer. Or could the answer be another possibility beyond those that I listed? If you’re curious, philosopher David Chomers believes the answer is possibility five. That is that the real you at the end is the electronic brain that ends up in your body. Let me know what explanation you think is correct in the comments below. And if you found

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