Thank you so much for your questions! :) Some quick thoughts:
If the human brain operates according to the known laws of physics, then in principle we could simulate it on a modern computer, and it would behave identically to the real thing (i.e. would respond in the same way to the same stimuli, and claim to see a purple ball with grandmaâs face on it if given simulated LSD).
The brain operating according to the known laws of physics doesnât imply we can simulate it on a modern computer (assuming you mean a digital computer). A trivial example is certain quantum phenomena. Digital hardware doesnât cut it. And even if you do manage to simulate certain parts of the system, the only way to get it to behave identically to the real thing is to use the real thing as the substrate. For example, sure, you can crudely simulate the propagation of light on a digital computer, but in order for it to behave identically to the real thing, youâd have to ensure e.g. that all âobserversâ within your simulation measure its propagation speed to be c. I donât believe you can do that given the costs of embodiment of computers.
Would such a brain simulation have qualia according to your view? Yes, no, or you donât think the brain operates according to known laws of physics?
It would be trivial âqualia dust,â like most electromagnetic phenomena (which are not globally bound). (I do think that the brain operates according to the laws of physics.)
If (1) is answered no, what would happen if you gradually replaced a biological brain with a simulated brain bit by bit, replacing sections of the cells one at a time with a machine running a simulation of its counterpart? What would that feel like for the person? Their consciousness would slowly be disappearing but they would not outwardly behave any differently, which seems very odd.
I think âgradually replacing the biological brain with a simulated brain bit by bitâ begs the question. For example, what would it mean to replace a laser beam âbit by bitâ?
If (1) is answered yes, does that mean that whatever this strange property of the EM field is, it will necessarily be possessed by the inner workings of the computer as well, when this simulation is run?
Just to be clear, Iâm not claiming that the EM field has some additional strange property, but rather that the EM field as it is is conscious (cf. dual-aspect monism). Also consider: When you talk about âthe simulation being run,â where exactly is the simulation? In the chips? In sub-elements of the chips? On the computer screen? Simulations, algorithms, etc. donât have clearly-delineated boundaries, unlike our conscious experience. This is a problem.
If all the fields of physics are made of qualia, then everything is made of qualia, including the electron field, the quark fields, etc?
I believe that to be the most parsimonious and consistent view, yes.
The brain operating according to the known laws of physics doesnât imply we can simulate it on a modern computer (assuming you mean a digital computer). A trivial example is certain quantum phenomena. Digital hardware doesnât cut it.
Could you explain what you mean by this..? I wasnât aware that there were any quantum phenomena that could not be simulated on a digital computer? Where do the non-computable functions appear in quantum theory? (My background: I have a PhD in theoretical physics, which certainly doesnât make me an expert on this question, but Iâd be very surprised if this was true and Iâd never heard about it! And Iâd be a bit embarrassed if it was a fact considered âtrivialâ and I was unaware of it!)
There are quantum processes that canât be simulated efficiently on a digital computer, but that is a different question.
Thanks, and sorry, I could have been more precise there. I guess I was thinking of the fact that, for example, some quantum systems would take, I donât know, the age of the universe to compute on a digital computer. And as I hinted in my previous response, the runtime complexity matters. I illustrated this point in a previous post, using the example of an optical setup used to compute Fourier transforms at the speed of light, which you might find interesting. Curious if you have any thoughts!
Thanks for the link, Iâve just given your previous post a read. It is great! Extremely well written! Thanks for sharing!
I have a few thoughts on it I thought Iâd just share. Would be interested to read a reply but donât worry if it would be too time consuming.
I agree that your laser example is a good response to the âreplace one neuron at a timeâ argument, and that at least in the context of that argument, computational complexity does matter. You canât replace components of a brain with simulated parts if the simulated parts canât keep up with the rest. If neurons are not individually replaceable, or at least not individually replaceable with something that can match the speed of a real neuron, (and I accept this seems possible) then I agree that the âreplace one neuron at a timeâ thought experiment fails.
Computational complexity still seems pretty irrelevant for the other thought experiments: whether we can simulate a whole brain on a computer, and whether we can simulate a brain with a pencil and paper. Sure, itâs going to take a very long time to get results, but why does that matter? Itâs a thought experiment anyway.
I agree with you that the answer to the question âis this system conscious?â should be observer independent. But I didnât really follow why this belief is incompatible with functionalism?
I like the âreplace one neuron at a timeâ thought-experiment, but accept it has flaws. For me, itâs that we could in principle simulate a brain on a digital computer and have it behave identically, that convinces me of functionalism. I canât grok how some system could behave identically but its thoughts not âexistâ.
I really appreciate your feedback and your questions! đ
Iâd love to reply in detail but it would take me a while. đ But maybe two quick points:
On observer independence: The main challenge that computational functionalism faces (IMO) is that thereâs no principled way to say âTHIS is the (observer-independent) system I posit to be consciousâ because algorithms, simulations, etc. donât have clearly-defined boundaries. Itâs up to us (as conscious agents) to arbitrarily determine those boundaries, so anything goes! The section âIs simulation an intrinsic property?â in this post sums it up quite neatly, I think. Field topology, as well as, say, entanglement networks, do give us observer-independent boundaries.
On the simulation behaving identically to the brain: Here I think one could reasonably ask: What if, in order for the simulation to behave identically, we had to simulate the brain even at the smallest physical scale? Many people think this isnât necessary and that the âneuron as digital switchesâ abstraction is enough. But say we actually had to simulate EM field phenomena, quantum phenomena, etc. Then I think runtime complexity matters, since maybe some parts of the brain can be simulated easily and others take millions of years. Can one bootstrap a coherent simulation from that? Now imagine trying to simulate multiple brains interacting with each other, running physics experiments, etc. Can one set up the simulation such that e.g. they all measure the speed of light to be the same? Or otherwise always get the same experimental results? I kind of doubt so. But regardless, the previous point about observer dependence would still stand.
Thank you so much for your questions! :) Some quick thoughts:
The brain operating according to the known laws of physics doesnât imply we can simulate it on a modern computer (assuming you mean a digital computer). A trivial example is certain quantum phenomena. Digital hardware doesnât cut it. And even if you do manage to simulate certain parts of the system, the only way to get it to behave identically to the real thing is to use the real thing as the substrate. For example, sure, you can crudely simulate the propagation of light on a digital computer, but in order for it to behave identically to the real thing, youâd have to ensure e.g. that all âobserversâ within your simulation measure its propagation speed to be c. I donât believe you can do that given the costs of embodiment of computers.
It would be trivial âqualia dust,â like most electromagnetic phenomena (which are not globally bound). (I do think that the brain operates according to the laws of physics.)
I think âgradually replacing the biological brain with a simulated brain bit by bitâ begs the question. For example, what would it mean to replace a laser beam âbit by bitâ?
Just to be clear, Iâm not claiming that the EM field has some additional strange property, but rather that the EM field as it is is conscious (cf. dual-aspect monism). Also consider: When you talk about âthe simulation being run,â where exactly is the simulation? In the chips? In sub-elements of the chips? On the computer screen? Simulations, algorithms, etc. donât have clearly-delineated boundaries, unlike our conscious experience. This is a problem.
I believe that to be the most parsimonious and consistent view, yes.
Thanks for the reply, this definitely helps!
Could you explain what you mean by this..? I wasnât aware that there were any quantum phenomena that could not be simulated on a digital computer? Where do the non-computable functions appear in quantum theory? (My background: I have a PhD in theoretical physics, which certainly doesnât make me an expert on this question, but Iâd be very surprised if this was true and Iâd never heard about it! And Iâd be a bit embarrassed if it was a fact considered âtrivialâ and I was unaware of it!)
There are quantum processes that canât be simulated efficiently on a digital computer, but that is a different question.
Thanks, and sorry, I could have been more precise there. I guess I was thinking of the fact that, for example, some quantum systems would take, I donât know, the age of the universe to compute on a digital computer. And as I hinted in my previous response, the runtime complexity matters. I illustrated this point in a previous post, using the example of an optical setup used to compute Fourier transforms at the speed of light, which you might find interesting. Curious if you have any thoughts!
Thanks for the link, Iâve just given your previous post a read. It is great! Extremely well written! Thanks for sharing!
I have a few thoughts on it I thought Iâd just share. Would be interested to read a reply but donât worry if it would be too time consuming.
I agree that your laser example is a good response to the âreplace one neuron at a timeâ argument, and that at least in the context of that argument, computational complexity does matter. You canât replace components of a brain with simulated parts if the simulated parts canât keep up with the rest. If neurons are not individually replaceable, or at least not individually replaceable with something that can match the speed of a real neuron, (and I accept this seems possible) then I agree that the âreplace one neuron at a timeâ thought experiment fails.
Computational complexity still seems pretty irrelevant for the other thought experiments: whether we can simulate a whole brain on a computer, and whether we can simulate a brain with a pencil and paper. Sure, itâs going to take a very long time to get results, but why does that matter? Itâs a thought experiment anyway.
I agree with you that the answer to the question âis this system conscious?â should be observer independent. But I didnât really follow why this belief is incompatible with functionalism?
I like the âreplace one neuron at a timeâ thought-experiment, but accept it has flaws. For me, itâs that we could in principle simulate a brain on a digital computer and have it behave identically, that convinces me of functionalism. I canât grok how some system could behave identically but its thoughts not âexistâ.
I really appreciate your feedback and your questions! đ
Iâd love to reply in detail but it would take me a while. đ But maybe two quick points:
On observer independence: The main challenge that computational functionalism faces (IMO) is that thereâs no principled way to say âTHIS is the (observer-independent) system I posit to be consciousâ because algorithms, simulations, etc. donât have clearly-defined boundaries. Itâs up to us (as conscious agents) to arbitrarily determine those boundaries, so anything goes! The section âIs simulation an intrinsic property?â in this post sums it up quite neatly, I think. Field topology, as well as, say, entanglement networks, do give us observer-independent boundaries.
On the simulation behaving identically to the brain: Here I think one could reasonably ask: What if, in order for the simulation to behave identically, we had to simulate the brain even at the smallest physical scale? Many people think this isnât necessary and that the âneuron as digital switchesâ abstraction is enough. But say we actually had to simulate EM field phenomena, quantum phenomena, etc. Then I think runtime complexity matters, since maybe some parts of the brain can be simulated easily and others take millions of years. Can one bootstrap a coherent simulation from that? Now imagine trying to simulate multiple brains interacting with each other, running physics experiments, etc. Can one set up the simulation such that e.g. they all measure the speed of light to be the same? Or otherwise always get the same experimental results? I kind of doubt so. But regardless, the previous point about observer dependence would still stand.