But there is a third possibility that might seem to offer more hope. This is the possibility of gradual brain replacement. Under this scenario a person might gradually have his regular human neurons (the cells in his brain) replaced with electronic units, perhaps some kind of artificial neuron. This process would avoid the sudden and abrupt transition that might come from an “all at once” mind uploading.
For example, every week during twenty consecutive weeks, a person might have one twentieth of his neurons replaced with electronic units. Since the electronic units might take up less space, there might at the end of this process be enough room in the skull to allow the person to eventually have an entirely electronic brain with a number of artificial neurons twice as great (or perhaps even ten times as great) as the number of neurons in the average human brain.
After the process was finished, the person might be much smarter. Another advantage is that he might then have a brain capable of lasting for centuries. The next steps might be replacing the other vital organs with electronic substitutes. The person might then gradually transition from a mortal body of flesh and blood to a potentially immortal body of silicon, plastic, and steel.
Those who imagine such a scenario suppose that as a person's brain was gradually replaced, the new electronic parts would be seamlessly integrated with the old parts of the brain, the parts made of flesh and blood. But getting the two parts to mesh together seamlessly might be enormously difficult.
There is a horrible possibility that few have considered. It might be that when you had some of your brain replaced with electronic parts, those parts would tend not to link with the old flesh and blood parts of your brain, but would instead tend to link together to form a second consciousness or personality in your brain. Gradual brain replacement might be a ticket to a split personality.
In such a case we can imagine a person with basically two brains in his skull – the old brain consisting of flesh and blood neurons, and the new brain consisting of electronic components. The two brains might vie for control over the muscles and limbs below the neck.
So with gradual brain replacement there would therefore be a chance for a new type of Jekyll and Hyde scenario. I can imagine future legal defenses like this: I didn't kill my wife; the electronic part of my brain did it.
Another terrifying possibility is that as you underwent gradual brain replacement, rather than feeling that your brain was getting smarter, you might feel that your brain was getting weaker, and that you were losing control over your body, as some foreign electronic consciousness in your skull took control of your body. This is exactly what could happen if more and more of your natural neurons were replaced with artificial neurons, and those neurons failed to seamlessly integrate with the rest of your neurons, forming instead a second consciousness or personality inside your skull. It would be like you were Personality X, and the new electronic neurons were forming Personality Y. As Personality Y got stronger and stronger, and smarter and smarter, your personality (Personality X) might get weaker and weaker and stupider and stupider.
An analogy is that when immigrants from very different lands are introduced into our society, we hope they will assimilate gracefully, becoming like the existing inhabitants and working well with them. But sometimes immigrants fail to do that, and instead form their own society with its own agenda (for example, La Cosa Nostra). Something like that could happen in your brain if you replaced part of your neurons with artificial units.
Someone might argue that things could not get too out of hand, because in a scenario I have imagined you could always alert the doctors that something had gone wrong. But maybe by then you wouldn't be in the driver's seat of your body – maybe your dwindling consciousness would be like someone stuffed in the back trunk (with the electronic part of your brain in the driver's seat).
Perhaps the best way to illustrate such a danger is through a science fiction story. Below is a tale of a man who underwent gradual brain replacement, and lived to regret it.
Gradual Brain Replacement: A Science Fiction Story
So here I am, unable to see anything, unable to hear anything, unable to smell anything, unable to move a muscle, and unable to feel anything. I have only a week left to live – I mean the real me, not that electronic thing that took over my brain – so I might as well review (in what's left of my mind) the whole horrible story.
In the year 2051 when people started doing that new thing called mind uploading, I knew it wasn't for me. Mind uploading was that deal where they destructively scan your brain, and supposedly transfer all your memories to the computer inside a robot body. Sure there were cases where a person had his mind uploaded into a robot body, and then the robot came to life and starting saying, “I'm the same John Smith who used to have a flesh and blood body, so bury the ruined protoplasmic body of the old John Smith.” But how can you be sure that in those cases John Smith didn't really die, just to be replaced by a new electronic person, who got some of John's memories? You can't. So I wanted to try something different: gradual brain replacement. I figured that was safer, that it would preserve the real me.
Gradual brain replacement works like this: bit by bit, over a period of a few months, they gradually replace all the neurons in your brain with electronic artificial neurons. The 3D TV commercials promise that this preserves the real you, and that nothing can go wrong, because if you notice something wrong at some point in the gradual process, you can just tell the doctors to stop doing anything more.
When I went into the doctor's office, he told me I had made a smart decision, and that everything would go fine.
“Gradual brain replacement is the way to go,” said Dr. Preston. “You'll be able to think a lot faster once the operations are done, and you'll be able to remember a lot more. Plus there's the fact that it's basically the first step to immortality. Once you don't have to worry about your brain wearing out, you can later get your other organs replaced, and plan on living for hundreds of years.”
So I told Dr. Preston to get started with the first operation. When I woke up after the operation, my mind seemed pretty much like it was before. Dr. Preston told me it would be a while before I noticed anything different. Then I left the hospital.
When I was walking into the parking lot, I noticed something very strange. The fingers on my right hand seemed to be moving all by themselves, even though I wasn't willing them to move.
The next day I opened the door to the refrigerator, and started reaching for an apple with my left hand. Then all of a sudden my right hand started reaching for a juice bottle. But I hadn't willed for my hand to reach for that juice bottle. It had somehow happened all by itself.
Then later while talking to my wife, I started saying words that came out of nowhere. I hadn't willed my lips to say the words. It was as if my lips were speaking all by themselves.
I sat down to think about what was happening. There was only one explanation. The new electronic neurons they had put in my head were somehow acting as an independent mind. The new electronic neurons hadn't integrated with the old biological neurons in my brain. Instead of there being a single enhanced mind inside my brain, there were now two minds inside my brain: my old mind, and a new electronic mind. And the two of them were in conflict. They weren't on the same page. I had no idea what the new electronic mind was thinking.
I tried to call Dr. Preston to tell him about the problem. But every time I picked up the phone and tried to dial with my left hand, my right hand grabbed the phone and threw it to the floor. So I simply decided that I would wait for my upcoming appointment with Dr. Preston at the hospital, and I would tell him the whole story at that time.
Over the next few days I found myself hearing my lips saying more and more things I hadn't told my lips to say. I also felt my hands doing more and more things I hadn't willed them to do. These were the actions of my new electronic neurons that had formed their own independent mind. I had no idea what that mind was thinking.
Finally the day of my appointment arrived. I waited in Dr. Preston's office. He came in and asked me: “So do you want us to proceed with the next operation, the next phase in the gradual brain replacement?”
I willed myself with all my might to say: “No.” But the words that came out of my lips were: “Yes.” The new electronic mind inside my brain had got the upper hand, and was becoming more and more dominant.
There was still one thing I could do. I still had control of my left hand. So I made my fingers into a “Thumbs down” gesture, trying to say “No” in the only way I could.
But Dr. Preston didn't notice. He took me over to a room in the hospital where they started to prepare me for the next operation. I tried to scream as hard as I could, but my lips were no longer in my control. They put me under anesthesia. The operation was going to replace even more of my biological neurons with new electronic neurons.
When I woke up, I found I no longer had any control over my lips or my eyes or my hands or my feet. It wasn't like I was paralyzed. I moved around and talked. But it wasn't me controlling the movements and controlling what my lips said. It was the new electronic mind in my brain. That mind was now completely in charge of all of my speech and movements. It was like I had been shoved to the back seat of my body, and the new electronic mind was in the driver's seat. All I could do was enjoy the ride.
Dr. Preston thought the operation had gone flawlessly. He saw me moving around okay, and speaking intelligently. But it wasn't me speaking and moving – it was that damned new electronic mind.
For two weeks I lived a life of passive observation. I could still see my body moving around and talking and meeting people. I just had not one bit of control over what my body did. It was just like passively watching television.
Then my body arrived back at the hospital, for one more operation in the gradual brain replacement operation. I was put under anesthesia. When I awoke, I was horrified. I could no longer see anything. I could no longer feel anything. I could no longer hear anything. I could no longer smell anything.
All I could do was make a deduction. The latest operation must have given exclusive use of my senses to the new electronic mind in my brain, which must now be using up a larger fraction of my brain. That's why I can no longer see or hear or smell or feel.
I also find my memory fading. I can no longer remember where I was born, or what land I live in, or what planet I live on, or who my parents or children are. The new electronic mind must be using up more and more of my memory.
Almost the only thing I can remember is that the final operation in the gradual brain replacement process will take place next week. By then my skull will contain an entirely electronic brain. The only problem is, it won't be my mind. It will be the mind of some weird new electronic thing. The real me will die as soon as my last biological neuron is replaced.
Why did I ever sign up for that gradual brain replacement?