Ray Kurzweil - How to Create a Mind - The Secret of Human Thought Revealed

Our conclusion? You 2 is conscious but is a different person than you—You 2 has a different identity. S/he is extremely similar, much more so than a mere genetic clone, because s/he also shares all of your neocortical patterns and connections. Or I should say s/he shared those patterns at the moment s/he was created. At that point, the two of you started to go your own ways, neocortically speaking. You are still around. You are not having the same experiences as You 2. Bottom line: You 2 is not you.

Okay, so far so good. Now consider another thought experiment—one that is, I believe, more realistic in terms of what the future will bring. You undergo a procedure to replace a very small part of your brain with a nonbiological unit. You’re convinced that it’s safe, and there are reports of various benefits.

This is not so far-fetched, as it is done routinely for people with neurological and sensory impairments, such as the neural implant for Parkinson’s disease and cochlear implants for the deaf. In these cases the computerized device is placed inside the body but outside the brain yet connected into the brain (or in the case of the cochlear implants, to the auditory nerve). In my view the fact that the actual computer is physically placed outside the actual brain is not philosophically significant: We are effectively augmenting the brain and replacing with a computerized device those of its functions that no longer work properly. In the 2030s, when intelligent computerized devices will be the size of blood cells (and keep in mind that white blood cells are sufficiently intelligent to recognize and combat pathogens), we will introduce them noninvasively, no surgery required.

Returning to our future scenario, you have the procedure, and as promised, it works just fine—certain of your capabilities have improved. (You have better memory, perhaps.) So are you still you? Your friends certainly think so. You think so. There is no good argument that you’re suddenly a different person. Obviously, you underwent the procedure in order to effect a change in something, but you are still the same you. Your identity hasn’t changed. Someone else’s consciousness didn’t suddenly take over your body.

Okay, so, encouraged by these results, you now decide to have another procedure, this time involving a different region of the brain. The result is the same: You experience some improvement in capability, but you’re still you.

It should be apparent where I am going with this. You keep opting for additional procedures, your confidence in the process only increasing, until eventually you’ve changed every part of your brain. Each time the procedure was carefully done to preserve all of your neocortical patterns and connections so that you have not lost any of your personality, skills, or memories. There was never a you and a You 2; there was only you. No one, including you, ever notices you ceasing to exist. Indeed—there you are.

Our conclusion: You still exist. There’s no dilemma here. Everything is fine.

Except for this: You, after the gradual replacement process, are entirely equivalent to You 2 in the prior thought experiment (which I will call the scan-and-instantiate scenario). You, after the gradual replacement scenario, have all of the neocortical patterns and connections that you had originally, only in a nonbiological substrate, which is also true of You 2 in the scan-and-instantiate scenario. You, after the gradual replacement scenario, have some additional capabilities and greater durability than you did before the process, but this is likewise true of You 2 in the scan-and-instantiate process.

But we concluded that You 2 is not you. And if you, after the gradual replacement process, are entirely equivalent to You 2 after the scan-and-instantiate process, then you after the gradual replacement process must also not be you.

That, however, contradicts our earlier conclusion. The gradual replacement process consists of multiple steps. Each of those steps appeared to preserve identity, just as we conclude today that a Parkinson’s patient has the same identity after having had a neural implant installed. 22

It is just this sort of philosophical dilemma that leads some people to conclude that these replacement scenarios will never happen (even though they are already taking place). But consider this: We naturally undergo a gradual replacement process throughout our lives. Most of our cells in our body are continuously being replaced. (You just replaced 100 million of them in the course of reading the last sentence.) Cells in the inner lining of the small intestine turn over in about a week, as does the stomach’s protective lining. The life span of white blood cells ranges from a few days to a few months, depending on the type. Platelets last about nine days.

Neurons persist, but their organelles and their constituent molecules turn over within a month. 23 The half-life of a neuron microtubule is about ten minutes; the actin filaments in the dendrites last about forty seconds; the proteins that provide energy to the synapses are replaced every hour; the NMDA receptors in synapses are relatively long-lived at five days.

So you are completely replaced in a matter of months, which is comparable to the gradual replacement scenario I describe above. Are you the same person you were a few months ago? Certainly there are some differences. Perhaps you learned a few things. But you assume that your identity persists, that you are not continually destroyed and re-created.

Consider a river, like the one that flows past my office. As I look out now at what people call the Charles River, is it the same river that I saw yesterday? Let’s first reflect on what a river is. The dictionary defines it is “a large natural stream of flowing water.” By that definition, the river I’m looking at is a completely different one than it was yesterday. Every one of its water molecules has changed, a process that happens very quickly. Greek philosopher Diogenes Laertius wrote in the third century AD that “you cannot step into the same river twice.”

But that is not how we generally regard rivers. People like to look at them because they are symbols of continuity and stability. By the common view, the Charles River that I looked at yesterday is the same river I see today. Our lives are much the same. Fundamentally we are not the stuff that makes up our bodies and brains. These particles essentially flow through us in the same way that water molecules flow through a river. We are a pattern that changes slowly but has stability and continuity, even though the stuff constituting the pattern changes quickly.

The gradual introduction of nonbiological systems into our bodies and brains will be just another example of the continual turnover of parts that compose us. It will not alter the continuity of our identity any more than the natural replacement of our biological cells does. We have already largely outsourced our historical, intellectual, social, and personal memories to our devices and the cloud. The devices we interact with to access these memories may not yet be inside our bodies and brains, but as they become smaller and smaller (and we are shrinking technology at a rate of about a hundred in 3-D volume per decade), they will make their way there. In any event, it will be a useful place to put them—we won’t lose them that way. If people do opt out of placing microscopic devices inside their bodies, that will be fine, as there will be other ways to access the pervasive cloud intelligence.

But we come back to the dilemma I introduced earlier. You, after a period of gradual replacement, are equivalent to You 2 in the scan-and-instantiate scenario, but we decided that You 2 in that scenario does not have the same identity as you. So where does that leave us?