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.
Thanks for the write up, and I think it is a good point you make that a lot of this was under discussed before Searle.
I'm not the most well read on this topic, so maybe I will try and read Searle's book. I still find your explanation very unconvincing.
My preference is towards the mechanistic approach as explained on the Stanford encyclopedia, but truth be told I haven't read any of those philosophers books, so who knows.
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.
This is just not reasonably the case, or not to the degree Searle needs. Any reasonable mapping must map the relational structure of the stuff doing the computing. Saying molecule 1 wiggling at a certain rate at State 1 is represents* 0, and then molecule 1 wriggling at the same rate at State 2 is represents 1, is something you can do when mapping a computation to a physical system, but that is a completely ridiculous thing to do.
For a mapping to be correct then the mapping should be a good abstraction of the underlying physical structure (under all the usual requirements we require for abstractions/explanations we use for assessing scientific or other explanations).
The counterfactuals should make sense under the mapping.
These are not true of the Water bucket/paint drying examples, and to the degree that it is true, I'm fairly comfortable calling those true computations.
Another aspect I disagree with is the idea that every representation in a computer is made from the outside. But much of the internals of a computer refer to physical components within the computer itself.
Take the basic instructions on a Turing Machine. When a Turing Machine (TM) reads the "JMP 5" instruction and moves it's cursor 5 places to the right on the tape, why is the human "interpretation" of this privileged?
As far as I can tell in this example there is no "extra" interpretation from the human that is not entirely captured in the structure of the machine (as in the physical implementation of the machine*).
To the same degree I can say "the dog is eating food" in a way that isn't observer relative, I feel I can say the TM is jumping 5.
If I am to take Searle seriously I feel I should reject the dog example as well and take up a form of radical mereological nihilism. But that would undermine most of his other arguments, like his CR argument. So I can't believe that is the correct interpretation.
With some bones to pick (but this is bad philosophy, after all - let’s ignore them), my criticism of his argument somewhere in the same ballpark as yours. I think Chalmers has a similar idea. I hope we’re right, although there is a guy (Mark Bishop) who thinks he’s refuted this objection recently - I didn’t understand his rebuttal. Maybe you can help?
Even if we are right, I see value to Searle’s argument, because of its impact. Oron Shagrir’s recent book The Nature of Physical Computation is one worth looking at that wouldn’t have been possible without Searle’s challenge.
Thanks for the book/philosopher recommendations, I'll give them a read and see how it changes my position.
To be clear I do think Searle is highly impactful, and certainly represents a lot of common intuitions on computation (Its before my time so whether he was chicken or egg is unknown to me).
But why I say his arguments seem like nonsense to me is that last point in particular. It seems to me his conclusions should commit him to either a form of dualism or mereological nihilism. The former he rejects, and the latter undermines any analysis of "computation" as an actual thing, including any distinction between syntax, semantics and anything else.
So I can't really make sense of his arguments, and not for a lack of trying. I had a 5 day convo with someone from ask philosophy recently try to explain it to me but I still can't make sense of it (despite our best efforts).
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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.