I was reading an article by J Mark Bishop "The danger of artificial stupidity" on ScientaSalon, where he quotes his own research, John Searle and Hilary Putnam, among others, as proof of the impossibility of strong AI. I've always felt that strong AI deniers were closeted substance-dualists. People who believed in souls, but were unwilling to come clean about their religious/metaphysical beliefs for fear of being ridiculed. So instead they come up with all sorts of pragmatic arguments against strong AI like qualia or computers lack of insight, which don't really hold.

My reasoning for why denying the possibility of strong AI implies substance dualism is the following:

  1. Any finite sized physical phenomena can be reproduced given sufficient technological means and a sufficient understanding of the underlying physical processes.

  2. Denying the possibility of strong AI means that no matter how advanced our technology and how comprehensive our knowledge of neuroscience and psychology will become, we will never be able to reproduce the functionality of the human mind.

  3. Per 1) The only reason we would not be able to reproduce the mind's functionality is if there is something non-physical about how the mind works.

  4. Saying there is something non-physical about how the mind works is the same as substance dualism.

My question is the following: Is this indeed the case, that denying the possibility of strong AI implies substance dualism?

  • what's "AI"? Artificial Intelligence? if so, "AI" in some different terms than what Computer Scientists mean (like "Expert Systems" or "Machine Cognition" or similar)? or "AI" in some deeper metaphysical sense? and what is "strong AI"? (or "weak AI"?) Mar 12, 2015 at 1:43
  • I mean strong Artificial Intelligence. Mar 12, 2015 at 2:31
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    By strong AI, I mean whatever combination f expert systems, machines learning algorithms, fuzzy logic, genetic algorithms, support vector machines,...you name it, necessary to simulate all of the functions of a normal educated adult mind. Mar 12, 2015 at 4:00
  • okay, so "AI" means "Artificial Intelligence". dunno if it's the "AI" like computer geeks think about it or if it's more of a Ray Kurzwiel thing about one's sense of consciousness existing among silicon-based technology rather than carbon based. and then i still dunno what is meant by "strong Artificial Intelligence". what's with the "strong"? Mar 12, 2015 at 4:01
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    @virmaior I changed the question according to your suggestion. I am conflating souls and substance dualism, but not out of if ignorance. That is the exact gist of my question: The way I see it, a property dualist account of the soul is perfectly compatible with strong AI, since a property dualist (hylomorphic or other) soul is to the brain what software to a silicone based computer. Am I missing any other possibilities? (oh and thanks for the condescension - classy) Mar 12, 2015 at 4:51

9 Answers 9


I think that people who claim strong AI is impossible do tend (often unwittingly) to commit themselves to some manner of dualism. But there is an argument to be made that the process is inscrutable:

We have no general theory for approximating arbitrary recurrent functions. Indeed, there are all sorts of recurrent functions with profoundly frustrating processes such as chaotic functions where long-term values cannot be predicted without infinitely accurate measurements of current states even when you know the form of the function.

Furthermore, our brains are heavily activity-dependent (synaptic plasticity, adaptation, etc. etc.). Therefore it plausibly could make a difference to the qualitative operation of the system what the long-term chaotic behavior is. (It is not guaranteed that it will, but it might.)

Thus, it is at least somewhat plausible that although our brains are in a universe which is nominally computable, in practice there is no way to find the computation that needs to be done. At every reduced level you run into exponentially hard problems (computational chemistry is too hard, protein folding is too hard, etc.), and at the highest level of abstraction there is no way to discover or verify the algorithm (and algorithmic space is enormous; you can't brute force the search).

This would, nonetheless, allow us to monitor and replay the entire activity of someone's brain (given almost unimaginable heroics of instrumentation and genetic engineering), but that is not strong AI. (It is very weird, especially from a philosophical standpoint: here you have a consciousness-over-time arrayed as patterns in space instead.)

Personally, I don't think this type of inscrutability is very likely, but the reasons for thinking so are more of a vague hunch about the evolvability of systems that rely upon details of chaotic behavior of self-recurrent systems than anything truly sound.

  • For neither your answer nor the OP do I grasp what you mean by "dualism". I can conceive of it as either a trivial proof where dualism is synonymous with the denial of reductionism OR the imputation that to deny mind-brain reductivism is to commit yourself to a Cartesian res mensa / res extensa dichotomy...
    – virmaior
    Mar 12, 2015 at 9:22
  • @virmaior - I was assuming that the OP meant the latter (and that the denial is a denial that even in principle it is impossible, not merely that you couldn't be sure, couldn't do it practically, etc.).
    – Rex Kerr
    Mar 12, 2015 at 9:39
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    I'm not seeing the butterfly effect as a serious constraint. Strong AI does not require that the AI can reproduce the exact mental state of any particular individual over arbitrary time intervals. It is just that the AI is effectively the same as a human intelligence. The fact that the AI's "mental trajectory" will diverge from the mind on which it's initial state was based (assuming that's how it's constructed), is no different from the fact that the trajectory of your mind is (almost certainly) radically different from mine.
    – Dave
    Mar 12, 2015 at 12:20
  • @Dave - I don't think your comment takes my third paragraph into account.
    – Rex Kerr
    Mar 12, 2015 at 12:26
  • WRT your third paragraph and @Dave s post, consider the state of someone's brain at this point in time. If it is so exquisitely sensitive to its initial state and/or its 'long term chaotic behavior' (if that is something different than the former) to the point that it cannot be successfully modeled, then it is extremely unlikely to continue working for any appreciable time, yet brains are routinely created in large numbers and work for extended periods. Therefore, the idea that there is some unobserved dependency on chaos here seems to be the sort of postulate that Occam's razor rejects.
    – sdenham
    Apr 6, 2018 at 14:33

I can think of a few alternatives:

  • One could argue for a case where a human mind grade AI is theoretically producible, but the universe lacks sufficient resources to do so. This would be a practicality argument, not a theoretical possibility argument.
  • Idealism can claim strong-AI is impossible, without being dualistic.
  • Not all finite sized physical phenomena can be reproduced. You have to be able to measure it first, and there may be unmeasurable values in the universe (QM has shown presumably unmeasurable values exist).

There is also the cheating argument, to claim that "strong AI" is not defined sufficiently to allow us to accomplish it, but I don't believe that is what you are looking for.

  • I have thought of each of those. In reverse order: 1) I don't buy the brain as a quantum computer. The mind is a macroscopic phenomena and quantum decoherence indicates a strong likely hood that the brain operates on a classical (non quantum level). Plus that would contradict the Church–Turing–Deutsch principle. Mar 12, 2015 at 3:46
  • 2) Idealism is logically possible, but I will follow previous examples and refute it by kicking my foot against a rock. I should have added that as a caveat in my original question, [disregarding idealism],...and would idealism produce a mirror symmetry of materialism, where the mind and the body would still follow the same set of rules, meaning strong AI is possible. Mar 12, 2015 at 3:52
  • 3) The mind as so complex that accurately simulating it is intractable is the most interesting retort all 3. I guess wouldn't dismiss it entirely, but I have to note that it puts serious strains on the holographic principle. That is the principle that the amount of information in a system is upper bound by the surface of the volume containing it. Maybe the mind is too complicated to be simulated by a laptop or 10 laptops. But is it truly so complex, that a machine with the equivalent power - say of the all of Google's hardware - can't simulate it? That would be far fetched, Mar 12, 2015 at 3:57
  • @AlexanderSKing in your order: 1) QM is one source of unmeasurable, it is simply the most accessible. Look into simulated automata and the idea of nonquiescent entities for a less accessible but less handwavey unmeasurable, also look into gardens of eden, which are not exactly in the direction you are looking, but are related enough to be of interest. 2) There is no guarantee that the idealistic form of materialism will choose(freewill) to free itself from whatever limitations material provided. However, I am fine to accept the caveat. I just wanted to point out that the decision is not binary
    – Cort Ammon
    Mar 12, 2015 at 15:36
  • As for 3, it depends on how high of fidelity you have to model the human brain. If it turns out it can be broken down into components (ALU, memory, cache, etc...) then it may be trivial to model. If the tiniest quirks have to be modeled for it to actually function, then this gets harder. As for the computing power, consider protein folding. Consider that proteins fold over a time on the order of a millisecond or less, and the body is constantly folding literally millions of proteins at any time. One protein fold on Folding@Home took 10million hour of CPU time.
    – Cort Ammon
    Mar 12, 2015 at 15:43

To complete Cort Amon's answer, I would say that there is a difference between reproducing physical phenomena and computing them.

Even if all physical systems can be reproduced using some physical material (say you reproduce the structure of a living cell from similar molecular components), that doesn't mean you can compute them. You only make physical copies of physical systems. Imagine that the only way to reproduce consciousness is creating a physical brain made out of similar organic components (neurons, ...) rather than implementing a software on a turing machine. Then strong AI would be impossible: computers are made out of transistors, not neurons, and you won't ever get the same result on a silicon computer, or any turing machine, even though dualism is false.

Note that contemporary physics is not computable, or only using strong approximations (and even then you only get probabilities). Also note that cloning a physical system is physically impossible (cf. the no cloning theorem) so even reproduction could be impossible...

Edit: here are some reasons why contemporary physics is not computable:

  • space-time is continuous, not discrete and you'd need infinite ressources for a bounded system. The idea that ultimate physics would be discrete is speculative.
  • physical quantities are irrational, not rational numbers and again you'd need infinite ressources
  • natural constants and measured quantities too, but we have finite measurement precision
  • a small imprecision can expand exponentially if the system is chaotic
  • in standard quantum mechanics, there are infinite series that we can only approximate through perturbation theory. In general, there is no analytic solution to the equations of the theory. Physicist often use classical approximations for interactions with external systems.
  • an open system might not be separable from its environment. We need idealisation even before we talk of "a system" (reduced density matrix).
  • in quantum field theories, we need further idealisations because of infinite divergence (renormalisation). (Although this could be solved by a future theory of quantum gravity, so if you consider an ideal physical theory in your argument this one is not necessarily an issue).
  • even when all these problems are addressed, computation time of quantum mechanics is exponential. Say it takes 1ms to compute 1ms, it could take 10ms to compute the next 1ms, 3 hours to compute the next 6ms, and 12 days to compute only 10ms in total...
  • as mentionned before, at this point you only get the probabilities...

Contemporary physicists cannot calculate the structure of complex molecules (up to a few atoms), even with huge computational capacities: they ask chemists to do this.

In sum, the conjecture today is that ultimate physics will be computable and it's an unlikely conjecture. Actual physics is not computable for many foundational reasons.

You could argue that it's not necessary to have all physical information: the substrate does not matter, only the "software" (the higher level) matters... But this is question begging. Why wouldn't the substrate matter for consciousness? Only when strong AI will be a success we'd know that it's the case.

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    "Note that contemporary physics is not computable": I would disagree with this statement, or at least say that it is a conjecture, not a fact. The Church–Turing–Deutsch principle (Deutsch, 1985) states the opposite. It an essentially physical extension of the Church-Turing thesis, stating that any physical process can be simulated (computed) by a Turing machine. Additionally, there are examples in nature of processes that follow intractable (NP-complete) computations - namely spin-glasses and protein folding - which end up in non optimal configurations exactly for that reason. Mar 12, 2015 at 3:40
  • (continued) - meaning nature is bound by the same limits that Turing machines are bound by. Moreover, if nature had physical processes that were non computable, we would simply turn that principle on its head and use those processes to solve undecidable/intractable problems. Mar 12, 2015 at 3:43
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    I edited my answer. I don't understand how we could turn the principle on its head... Perhaps look for ressources on the relation between quantum computing and NP hard problems-although it's tempting at first sight to think that quantum computers could solve NP hard problems (one reason the field is being developed), there are physical limitations that prevent it practically I think (it's a complex issue and I'm not an expert). Mar 12, 2015 at 10:01
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    A nit: people do alot more than "a few atoms" nowadays: wiki.simtk.org/openmm/BenchmarkOpenMMDHFR.
    – Dave
    Mar 12, 2015 at 11:58
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    Is this a reasonable summary of your first point: "Given that we don't really understand the relation between mind and brain, it is possible that the following is true: The presence of human-like-qualia requires that the mind exist in the context of biological neurons. A silicon brain would (necessarily) result in a mind with significantly different qualia."
    – Dave
    Mar 12, 2015 at 12:02

There are other alternatives; for example:

Spinozas system which encompasses mental and physical phenomena as modes of an absolute self-subsisting simple substance.

ln Leibnizs Monadology; there are many kinds of monads; a soul is a monad, as is God; they don't interact; each reflects in itself all the others; and harmonised independently.

In Epicurus's system all is atoms; and the soul is made of soul atoms; as such they can affect material atoms.

In Hegel; the world is the progression of the world-Geist from non-being and being; which in a sense are the same; thus human beings are an expression of the Geist.

Kant identifies a noumenal world behind the phenomenal world; one could take this inexpressible and indescrible dimension where mental and physical phenomena are 'one'; though he quiet on how the noumenal world causes the phenomenal world.

Schopenhauer identifies the noumena of an impersonal will; and it is the force of this will that causes the phenomenal world.

I would hazard a guess, that it was the admixture of Greek and Christian Philosophy that identified the absolute substance as God; and although Descartes is usually counted as the originator of the dual substance thesis; in fact, he's not, being too careful and cautious a thinker; one supposes it was the outcome of later cogitations by Descartians - but this removal of the metaphysical scaffolding left these hanging in the void, and unable to interact with each other by definition; as substances are causally closed.

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    I would argue that Leibniz and Epicurus are describing defacto substance dualism: Saying there are special soul monads or soul atoms - or soul superstrings or soul quarks for that matter) - amounts to saying that the soul has a type of substance different from the rest material objects. Mar 12, 2015 at 15:05
  • @king: good point - but substances are causally closed; atoms aren't; monads are - but Leibniz uses the notion of a prearranged harmony to mimic interaction or cause. Mar 12, 2015 at 15:11
  • Epicurus uses the existence of the will for example to deduce that atoms must display a certain 'willfulness' - ur the clinamen. Mar 12, 2015 at 15:13
  • I think the list of notions in this answer is fascinating. Starting with Spinoza's "absolute self-subsisting simple substance", what are some of the scientific experiments that imply that it exists, or experiments that show it doesn't exist? Also the "soul atoms" sound as something that must surely have interested experimenters, yes? May 24, 2015 at 5:58
  • @Cheersandhth.-Alf: can you show me an experiment that gives me an actual number - that I can hold in my hand? I mean your agenda appears to be to reduce everything to an experiment - if I can test for it, it must exist; in which case why not hang out in physics.SE; this is after all a site devoted to philosophy; and the empirical angle is just one small fragment of the edifice; plus it has a history - which is in part what I'm referring to. May 24, 2015 at 12:34

I think the ability to clearly define the 'strong' in 'strong AI' is equivalent to dualism.

If you do not think there is some inscrutable aspect of the human mind, then all AI is continuous with the behavior of young or impaired humans, and there is not some magical point where it becomes 'strong AI', equivalent to humans. In some aspects it is already superior, and in others it could compensate given adequate power or time.

If you consider genetic recombination as a form of computation, it has the power to create human intelligence, having done so. Given a different environment, it could create a different form. We also see it solve problems that we cannot solve, and we have to simply steal its solutions until we understand them. So that is an equally strong or better problem-solving system than human intelligence. Is it 'artificial' enough? It appears to be digital, and we think of it as quite mechanical -- the kind of thing we can emulate in machines.

If you do think there is this inscrutable aspect, only then can you really state any definition of 'strong AI' with meaning that truly separates it from 'a whole lot of weak AI'.

So the question ends up being baseless or circular. If you accept a functional (performative, Turing-esque) definition of strong AI, you do so only because you are not a dualist, and if you resist, you do so only because you are one.

  • Modulo the vagueness of the notion of substance dualism (the OP's choice of classification) this sounds pretty clear and convincing; upvoted. May 24, 2015 at 6:02

There are two reasons why it might be impossible to create an Artificial Intelligence with a mind equal to or better than that of a human: One reason could be that the building blocks of the brain are in some way superior to silicon chips or anything else that humans could create as the substrate for intelligence. The other reason could be that creating Artificial Intelligence is just very difficult, and human scientists and software developers are not clever enough to do it.

Substance dualism would be a subcategory of the first reason. But you could argue that the brain has about 10 to the eleventh power neurons, with each having on average 7,000 connections, and that is just a big number that beats current computer hardware. (On the other hand, the computer hardware runs a lot faster than the human brain's hardware). It is an argument for human-grade AI not being possible today, but not for the impossibility in the future. Substance dualism would be an argument for "impossible in principle".

The other argument that creating an AI is just very difficult is also one that doesn't speak for "impossible in principle". It might be that creating a computer which spends 18 years learning like a human is needed to create an AI. That would mean "not impossible". (Note that once such a computer had learned for 18 years, it could easily be duplicated, unlike humans).

So if there are claims that AI is in principle not possible, then attributing some mysterious quality to the human brain that humans can't reproduce would be one argument for such a claim.

Just a note: It is well-known that there are certain mathematical problems that computers cannot solve. But humans can't solve them either. Humans can choose to ignore such problems. An artificial intelligence would necessarily need the ability to ignore such problems as well.

  • You keep implying there should be other reasons... But can you give any? If not, the OP is correct.
    – user9166
    Mar 24, 2015 at 21:58
  • Why would I need to give other reasons? Someone who claims AI is impossible may have other reasons. He may be right or wrong, it doesn't matter; he can have other reasons. Therefore claiming that AI is impossible doesn't imply belief in substance dualism.
    – gnasher729
    Mar 24, 2015 at 23:41
  • That fails to be an argument, so this fails to be an answer to the question. You have given no evidence that he is right or wrong. Anyone might have a reason to doubt any fact. But that does not mean that every fact is equally open to question.
    – user9166
    Mar 25, 2015 at 3:10

With regard to your points 1 through 4, you have to be a bit more careful. Sure we could probably artificially produce something modelling a human thinking brain, substituting biological tissue by something else. I doubt any scientist would deny this possibility. But this is likely not what you, or anyone really understands by hard AI. Really we want a computational model of intelligence, a Turing machine running a very complicated program. It is difficult to "disprove" possibility of this, but there is very good reason to doubt possibility because of Godel's incompleteness theorem, and Turing's halting problem. It is bizare that this is not mentioned above. It would be difficult to give these things justice here, but some people have thought long and hard about the question, see for instance the books of Roger Penrose.

  • The Church-Turing-Deutsch , an extension of the original Chruch-Turing thesis published in the 80s, states that any physical process can be simulated by a Turing machine. Presumably, unless you're a substance dualist, you consider the brain to be a physical process. Also keep in mind that and Godel's and Turing's results were originally about computations performed by humans - based in the idea that an algorithm is any calculation that can performed in a finite number of steps. It is only later that they came to be interpreted as mainly being about artificial machines. May 22, 2015 at 13:27
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    Maybe you should read up: en.wikipedia.org/wiki/Church%E2%80%93Turing_thesis. The point is if the brain is falling back on a physical process, formalized by say a function A to B, such that this function is not algorithmically computable then we are not a Turing machine, end of story. What could be the process? That is very interesting once again I refer to Penrose for some nice speculations.
    – Yasha
    May 22, 2015 at 13:38
  • I am aware of Penrose's arguments and I disagree with them, see comments above. Again, please refer to the Church-Turing-Deutsch thesis en.wikipedia.org/wiki/… May 22, 2015 at 13:48
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    First of all, If you are aware of Penrose's arguments then I don't understand your original question. Certainly the views of Penrose have nothing to do with dualism. He is following concrete mathematical and physical ideas to arrive at his conclusions. Unless you are claiming that anyone who has doubts on computability of physical processes is somehow a dualist. Second please don' Church and Turing next to Deutsch
    – Yasha
    May 22, 2015 at 16:12
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    It is a radical departure/generalization from the essence of Church and Turing, and I somehow doubt they would approve. But let's not get sidetracked. In mathematics/science one never uses A-B-C for authors unless all authors asserted essentially the same statements.
    – Yasha
    May 22, 2015 at 16:57

The scientific consensus is almost overwhelming that strong AI is possible and substance dualism is inconsistent (unless you add a bunch of qualifiers to "impossible", which goes against Searle's original argument against Strong AI). Once we get that out of the way, in response to OP's actual question: Two incorrect beliefs do not have to imply each other. You have identified a set of assumptions that would equate the incorrect beliefs, but that does not mean a belief in one statement implies a belief in the other, as it is entirely possible that the "believer" has not taken into consideration the comprehensive implications of his belief. If this were to be the case all the time, we wouldn't need philosophical debates at all.

If your goal is to demonstrate that these statements are wrong, then you can simply attack each statement individually, since the equivalence you're drawing about beliefs in these statements adds no epistemological value to your argument.


No, not necessarily.

Consider Searle, known for his criticisms of AI research (or perhaps more accurately, of the claims staked already quite early on, with little to show for it).

Yet Searle says he is a physicalist (and by implication, a non-dualist). That is to say, he says that there are physical systems that think (e.g. our brains) and there is no reason to suppose that there could not be machines that think - since whatever physical principles are at work in our brains could presumably be replicated in a suitable sort of machine.

However, Searle also feels that the course set by computer science (and their associated philosopher friends) will not lead to a suitable sort of machine.

If I have understood him correctly, he maintains that we cannot be sure that we have understood all the physics that underpins mental processes (which I guess is true, strictly speaking) and I think he also claims that computers and software categorically lack that piece of missing physics.

The latter is problematic, as it hinges on precise definitions of what we mean by computer and software (CS 101, I know, but nonetheless tricky to apply to this question) and on characterising this bit of physics of which the nature remains undetermined.

The latest spate of kind-of-OK AI-generated imagery, prose, and translations may impress some, but will suggest to others that, as Searle would have it, an essential ingredient is likely to remain lacking for some time to come. But I am not sure whether the missing ingredient really is a bit of yet-to-be-determined physics.

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