I think about this one often. The best comment is here:
You replace a single neuron in your brain with one that functions thousands of times faster than its biological counterpart.
Are you still you? You’d probably argue that you are, and even a significant speed bump in a single neuron is likely to go largely unnoticed by your conscious mind.
Now, you replace a second neuron. Are you still you? Again, yes. You still feel like yourself. You still have the continuity of experience that typically defines individuality. You probably still don’t notice a thing, and indeed, with only a couple of overachieving neurons, there wouldn’t be much to notice.
So, let’s ramp it up. You replace a million neurons in your brain with these new, speedy versions, gradually over the course of several months. Sounds like a bunch, right? Not really; you’ve still only replaced 0.001% of your brain’s natural neurons by most estimates. Are you still you? You may find you’re reading books a teensy bit faster now, and comprehending them more easily. An abstract math concept (say, the Monty Hall problem) that once confused you now begins to make some sense. You’re still very much human, though. You stubbed your toe this morning due to poor reflexes, resulting from a lack of sleep. You briefly felt lonely for a moment. That cute cashier turned you on as much as ever.
But why stop there? You’re feeling pretty good. You embark on a neurological enhancement regimen of two billion fancy new neurons every month for a year. After this time, you’ve got on the order of 24 billion artificial neurons in your head, or about a quarter of your brain. Are you still you? Your feelings and emotions are still intact, as the new neurons don’t somehow erase them; they just process them faster. Or they don’t, depending upon your preference. About half-way through this year, you began noticing profound perceptual changes. You’ve developed a partially eidetic memory. Your head is awash in curiosity and wonder about the world, and you devour Wikipedia articles at a rapid clip. Within weeks you’ve attained a PhD-level knowledge of twenty subjects, effortlessly. You have a newfound appreciation for music- not just classical, but all genres. All art becomes not just a moving experience, but an experience embedded in a transcendental web of associations with other, far-removed concepts. Synesthesia doesn’t begin to cover what you’re experiencing. But here’s the thing; it’s not overwhelming, not to your enhanced, composite brain and supercharged mind. Maybe you’ve subjected yourself to dimethyltriptamine or psilocybin before, and experienced a fraction of this type of perception. But this is very different. It feels so very soft and natural, like sobering up after a long night out.
You reason (extraordinarily quickly at this point, I might add), that since you don’t seem to have lost any of your internal experience, you should go whole hog, and replace the rest of it. After all, at this point, everyone else is, too. It’s getting harder to find work for someone who’s only a quarter upgraded. Over the next three years you continually add new digital neurons as your biological ones naturally die out. Are you still you? Following this, you are a genius by all traditional measures. Only the most advanced frontiers of mathematics and philosophy give you pause. Everything you’ve ever experienced, every thought that was ever recorded in your brain (biological or otherwise) is available for easy access in an instant. You became proficient in every musical instrument, just for the hell of it. Oh sure, you still had to practice; approximately ten minutes for each instrument. You’re still a social creature, though, and as such, you still experience sadness, love, nostalgia, and all other human emotions. But as with a note played on a Stradivarius violin as opposed to a simple electronic function generator, your emotions now have such depth, so many overtones. Your previous, unenhanced self could not have comprehended them. You are a god, but with the curiosity of a child. Though never religious, the phrase “born again” comes to your dizzyingly fast and complex mind.
Years pass. The same medical technology that allowed your neurons to be seamlessly replaced, aided and accelerated by a planetful of supersavants, has replaced much of your biological body as well. You’re virtually immortal. Only virtually, of course, because speeding toward Earth at a ludicrous velocity is a comet the size of Greenland. There is general displeasure that the earth will be destroyed (and just after we got smart and finally cleaned her up!), but there’s a distinct lack of existential terror. Everyone will be safe, because they are leaving. How does a civilization, even a very clever one, evacuate billions of people from a planet in the space of years? It builds some very large machines that circle the sun, and it uploads everyone to these machines. Uploads? People? Why sure, by now everyone has 100% electronic minds. If you’ve ever worked with a virtualized computer, or played a video game ROM from a long-defunct console on your new PC, you understand the concept already. These minds are simply software; in fact, they always were. Only now, they’re imminently accessible, and more importantly, duplicable.
Billions of bits of minds of people are beamed across the solar system to where the computers and their enormous solar panels float, awaiting their guests. Of course, just as with your neuronal replacements all those years ago, this is a gradual process. As neurons are transferred, their counterparts in your skull are disabled. The only difference you feel is a significant lag, sometimes on the order of minutes, due to the millions of miles of distance between one half of your consciousness and the other. Eventually, the transfer is complete, and you wake up in a place looking very familiar. Virtual worlds, mimicking the earth to nanometer resolutions, have already been prepared. In the real world, gargantuan fleets of robots, both nano- and megascopic, are ready to continue building new computers, and spacecraft, and new robots, as humankind prepares to seed the cosmos with intelligence. We haven’t achieved faster-than-light travel, but our immortal minds and limitless virtual realities make space and time irrelevant.
Are you still you?
Only one way to find out.
And the best reply:
“The ship wherein Theseus and the youth of Athens returned had thirty oars, and was preserved by the Athenians down even to the time of Demetrius Phalereus, for they took away the old planks as they decayed, putting in new and stronger timber in their place, insomuch that this ship became a standing example among the philosophers, for the logical question of things that grow; one side holding that the ship remained the same, and the other contending that it was not the same.”
A problem we’ve been considering since at least 350BC
Ah, but is it moral?