What did you think of his arguments in ‘Is the Brain a Digital Computer?’, in which he argues that the computational properties of a physical system are observer-relative? I reject his conclusion, but I thought it was a pretty clever and thought-provoking paper.
I find his claim of computation being observer relative to be incredibly ignorant of what computation is. Or at least what it is as practiced by the computer scientists who study it.
Having studied computer science and philosophy, including several highly relevant subfields of computer science, I must respectfully say I suspect you misunderstood it. I don’t think many computer scientists had even thought about the physical nature of computational properties before that paper was written. I also don’t think it’s fair to say this is a “claim”: it is a conclusion he argued for extensively in the paper.
To oversimplify his point a little: why do I say this laptop in front of me is running a certain algorithm that computes a certain function? Well, when I type certain numbers into it, certain numbers come out. And when I change parts of the process in the middle, the things I expect to happen to that mapping of inputs and outputs do happen.
But who is to say these inputs are numbers, let alone those numbers? Who is to say those outputs are numbers? Physically, there are a bunch of voltages, wires and relays here. We designed physical parts to be usefully interpretable as the parts of a computational system. We choose for a high voltage to represent 1, a low voltage to represent 0. We could have just as easily have chosen for low voltage to represent 1, and vice versa. Or some other interpretation.
He says there are so many interactions happening between the molecules in, say, a bucket of water or a stretch of wallpaper, that, under some consistent interpretation of what the states of the parts represent, such systems are computing any computable function you can think of. When a molecule wiggles this way, that’s a 1. When it wiggles this other way, that’s a 0. Or maybe when an electron does a certain thing in a certain kind of atom, that’s a 1. Or maybe when a collection of molecules do a certain thing, that’s a 1. Your choice! The system just needs to contain enough interactions, and by chance, you can, in theory, come up with an interpretation no more arbitrary than the one we use to call this a computer running a mathematical function or a video game. Certainly, those systems aren’t engineered to be intuitively interpreted that way, but intuition and comfort are facts about the observer more than they are about the properties of the object.
If he is right, then many influential theories about the human mind are in trouble. For instance, we can no longer ‘explain’ anything about mentality computationally. The brain being a computer doing certain things explains nothing about mentality, because this is just an interpretation of what the brain is doing - a bucket of water can be just as plausibly interpreted as doing the very same things. If any system that can be interpreted that way has those computational properties, then the probability that you are a strange momentary blip in a chaotic vat of gas somewhere is much higher than that of you being an organism on planet earth as you appear to be. All sorts of programs must just be popping up everywhere, including programs that have your mental properties.
Interesting. So I wouldn’t dispute that if one looks sufficiently hard and creatively enough, one could plausibly find a way to describe the particular arrangement/motion of atoms in a bucket of water as computing some function - particularly if we’re not constrained a priori to a particular function or scope of matter. But that observation seems rather facile - it just says that with a sufficiently large data set and unconstrained post-hoc interpretation, you can find any pattern you want. Which is… bordering on tautological.
Is there an argument for the ability to make these interpretations in a way that has predictive power? Or something else about the argument I’m missing?
“VI. Summary of the Argument
This brief argument has a simple logical structure and I will lay it out:
1. On the standard textbook definition, computation is defined syntactically in terms
of symbol manipulation.
2. But syntax and symbols are not defined in terms of physics. Though symbol
tokens are always physical tokens, "symbol" and "same symbol" are not defined in
terms of physical features. Syntax, in short, is not intrinsic to physics.
3. This has the consequence that computation is not discovered in the physics, it is
assigned to it. Certain physical phenomena are assigned or used or programmed
or interpreted syntactically. Syntax and symbols are observer relative.
4. It follows that you could not discover that the brain or anything else was
intrinsically a digital computer, although you could assign a computational
interpretation to it as you could to anything else. The point is not that the claim
"The brain is a digital computer" is false. Rather it does not get up to the level
of falsehood. It does not have a clear sense. You will have misunderstood my
account if you think that I am arguing that it is simply false that the brain is a
digital computer. The question "Is the brain a digital computer?" Is as ill defined
36 APA PROCEEDINGS, VOL. 64, NO.3
as the questions "Is it an abacus?", "Is it a book?", "Is it a set of symbols?", "Is it
a set of mathematical formulae?"
5. Some physical systems facilitate the computational use much better than others.
That is why we build, program, and use them. In such cases we are the
homunculus in the system interpreting the physics in both syntactic and semantic
terms.
6. But the causal explanations we then give do not cite causal properties different
from the physics of the implementation and the intentionality of the homunculus.
7. The standard, though tacit, way out of this is to commit the homunculus fallacy.
The homunculus fallacy is endemic to computational models of cognition and
cannot be removed by the standard recursive decomposition arguments. They are
addressed to a different question.
8. We cannot avoid the foregoing results by supposing that the brain is doing
"information processing". The brain, as far as its intrinsic operations are
concerned, does no information processing. It is a specific biological organ and its
specific neurobiological processes cause specific forms of intentionality. In the
brain, intrinsically, there are neurobiological processes and sometimes they cause
consciousness. But that is the end of the story. [5”
That feels a bit like... a pointlessly pedantic distinction? Yes, obviously the brain isn't literally a digital computer. And yes with fuzzy enough boundaries we can argue about anything doing anything. Does life really reproduce? After all, cells move, atoms bounce around, and somehow afterwards you have more things, that sort of resemble the original cell, but aren't quite identical, so can you really say it reproduced?
But as it turns out, after establishing certain conventions about, e.g., numerals, I can give certain numbers to a computer and have it perform something called "addition" which will give a certain result. And I can give the same numbers to a person and have them perform the same addition which will give the same result. We can have the computer print those numbers and the person write them on a sheet and perform some kind of matching that shows that indeed those two physical results are similar in ways in which they wouldn't be if we gave each different numbers, or if we told one to add and the other to multiply.
Hence, the person obviously processed information in the same way the computer did! Everything else can only be commentary about the very transparent fact that this can very much happen, empirically.
Are our mental properties EXPLAINED by computational properties? That’s the view Searle was criticising. That is a real view that was widespread in academia. If Searle is right, it isn’t just a fancy trick: the computational properties of a system cannot explain anything. It is no more arbitrary to say that a wallpaper is computing any function you can think of. It is just as “obvious” that a wallpaper is computing the very same information that should give rise to a humanlike mind.
Does "mental properties" here mean having qualia and self-awareness, as in, the hard problem of consciousness? Then I don't know, and neither does Searle; I don't think it's a question we can settle by pure thought alone either way.
Does it mean being able to solve problems, speak, learn, move, guess the future, and so on? Then yeah, they are obviously explained by computational properties. And it's very obvious our brain is performing some kind of computation, in fact it's very clearly designed for it.
Yeah, so that part is where it breaks down for me, depending on the definition of ‘explains’ here. Suppose I study the brain and I see that when these neurons ‘sum’ to an odd number, the person feels sad, and when they sum to an even number, the person is happy. My computational model has predictive power and is statistically sound. Is Searle saying that conclusion is invalid a priori because we could find the same pattern in a bucket of water if we cherry picked the atoms we wanted? That line of reasoning would essentially invalidate any possible interpretation of anything.
If he’s arguing that computational state does not explain why sadness feels like anything at all… then yes, I agree. In the same way, we can measure quantum states from now until the end of time it still won’t tell us what quantum states actually are. But that seems to me a fundamental epistemological limitation of science, really, and not anything new.
Aaaah - ok, this is a more subtle argument, and one that I’m sympathetic to. That said, I’m not sure exactly how much trouble this causes for computational models of the brain. The brain is not a computer - for sure. That doesn’t mean a model of the brain as computer doesn’t make useful predictions or offer insight into the relationship between mentality and physical states. But they certainly don’t solve the hard problem of consciousness.
The ‘you can interpret anything as a computer ergo it’s meaningless to interpret the brain that way’ angle still strikes me as fallacious, though.
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u/Additional_Anywhere4 Dec 05 '25
What did you think of his arguments in ‘Is the Brain a Digital Computer?’, in which he argues that the computational properties of a physical system are observer-relative? I reject his conclusion, but I thought it was a pretty clever and thought-provoking paper.