The Impossibility of Mind Uploading


My most recent post, “Living in a Computer Simulation,” elicited some insightful comments from a reader skeptical of the possibility of mind uploading. Here is his argument with my own brief response to it below.

My comment concerns a reductive physicalist theory of the mind, which is the view that all mental states and properties of the mind will eventually be explained by scientific accounts of physiological processes and states … Basically, my argument is that for this view of the mind, mind uploading into a computer is completely impractical due to accumulation of errors.

In order to replicate the functioning of a “specific” human mind within a computer, one needs to replicate the functioning of all parts of that specific brain within the computer. [In fact, the whole human body needs to be represented because the mind is a product of all sensations of all parts of the body coalescing within the brain. But, for the sake of argument, let’s just consider replicating only the brain.] In order to represent a specific human brain in the computer, each neuron in the brain would need a digital or analog representation, instantiated in hardware, software or a combination of the two. Unless this representation is an exact biological copy (clone), it will have some inherent “error” associated with it. So, let’s do a sort of “error analysis” (admittedly non-rigorous).

Suppose that the initial conditions of the mind being uploaded are implanted in the computer with no errors (which is highly unlikely in its own right). When the computer executes its simulation, it starts with that initial condition and then “marches in time”. The action potential duration for a single firing of a neuron is on the order of one millisecond, which implies that the computer time step would need to be no larger than that (and probably much smaller or else additional computational errors are induced). So the computer would be recalculating the state of the brain at least 1,000 times per second as it marches in time (and probably more like 10,000 times per second).

Since the computer representation of the brain is not perfect, errors will accumulate. For example, suppose that the computer representation of one neuron was only 90% accurate. After that neuron “fired”, its interaction with connected neurons would have roughly a 10% error. Now consider that the human brain has roughly 86 billion neurons, each with multiple connections to other neurons. The computer does not know which of those 86 billion neurons are needed at each time step, so all would need to be included in each calculation. One can see that 10% errors in the functioning of individual neurons within the millisecond duration will quickly accumulate to produce a completely erroneous representation of the functioning of the brain a short time after the computer started its simulation. The resulting “mind” that gets created in that computer would probably bear no similarity to the original human mind (or to probably any “human” mind). It would probably be “fuzzy” and unable to function.

Would 99% accuracy in the representation of a neuron be any better? Not really. 99.9% accuracy? Still no good. 86 billion neurons is a large number (and remember, the computer is recalculating the entire brain state 1,000 to 10,000 times per second). In order for accumulated errors to not overwhelm the simulation of the brain in the computer, the accuracy in representing each neuron would need to be extremely high and the amount of information needing to be stored for each of the 86 billion neurons would be huge, leading to an impractical data storage and retrieval problem. The only practical “computer” would be a biological clone, which is not the topic here.

Consequently, if one believes in a reductive physicalist theory of the mind, then uploading the specific mind of an individual human into a computer is, for all intents and purposes, impossible.

My Response 

Let me say briefly that I wouldn’t call mind uploading impossible, as many experts (Ray Kurzweil, Marvin Minsky, Randal A. Koene, Nick Bostrom, Michio Kaku, and others) attest to its possibility. And even skeptics like Kenneth Miller don’t reject the idea in principle. My view is that, with enough time for future innovation, something like it is almost inevitable. Of course we may not have that time.

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5 thoughts on “The Impossibility of Mind Uploading

  1. I intended to comment on the original post, but was too lazy to get around to it. I recommend the book “Descartes Error” on this topic. The thrust of this book is that the brain is too tightly integrated with the body to be considered separate from it. The brain is influenced by every aspect of body chemistry: not just hormone levels, but such simple things as glucose concentrations and salt concentrations in the bloodstream. Exercise alters the chemistry of the blood in ways that affect brain function.

    Thus, if you want to upload the brain, and get a system that truly replicates brain function, you’re going to need to re-create the ENTIRE human body: blood, heart, lungs, bones, kidneys, liver, muscle, and so forth. If you want to replicate its function digitally you’ll need precise digital simulations of every single chemical reaction in the body, every response to external stimuli such as light, temperature, humidity, and so forth.

    Yes, this is conceivable in principle. But it’s immensely more complicated than most people recognize, and utterly beyond our capabilities for the foreseeable future.

  2. John, thank you. Your point about my misuse of the term “impossible” is well taken.

    I agree that the concept of mind uploading is both “logically” possible (meaning that there are no inherent contradictions) and “physically” possible (meaning that there are no violations of laws of physics). Meeting those two tests make the concept theoretically possible. Thus, in my final assessment, instead of saying “for all intents and purposes, impossible”, I should have said “from an engineering perspective, impractical”.

  3. I very much doubt that reading the complete and precise state of a given human mind at a given time will ever be possible. Perhaps a good approximation will be achievable, but I expect even this would involve destruction of the brain in the process. Even if an exact working copy were embodied in silicon, The result would be a different consciousness, with a different body, and therefore different wants and needs and abilities and disabilities, and for that reason not really the same person at all.

  4. So, how many bits are you guys? I mean if you put yourselves on sheets of paper, your entirety up until now, how many ones and zeroes would you estimate you need? Could you bound it by saying what number is just flattery and what number is too meager to be who you are?

  5. The real problem is that, even if the simulation was 100.00% perfect–in fact, even if a 100.00% perfect physical clone was brought into existence at the moment of the destruction of the original brain/body, the original person is still dead. It simply doesn’t matter how perfect the copy is.

    If there’s any doubt about this, consider that the original wouldn’t have to be destroyed, that both the original and the copy could exist at the same time.

    So the question is: What is it that would still be dead? If identity is just a matter of information patterns, or memories, or structure, or likely all of these and more, then why isn’t this a path to immortality? What, exactly, is the “I” that cannot be said to have survived through the copying process? And why, precisely, can’t it be said to have survived?

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