I am struggling to understand the meaning of some of the terminology John Searle uses in "Mind, brains, and programs." For example, right before "IV. The combination reply," he writes that

The problem with the brain simulator is that it is simulating the wrong things about the brain. As long as it simulates only the formal structure of the sequence of neuron firings at the synapses, it won't have simulated what matters about the brain, namely its causal properties, its ability to produce intentional states.

What does "causal properties" really mean? I don't think it has to do with causation in the traditional sense (or if it does, I can't exactly see what he's going for here).

  • 2
    Intentional states are those mental states such as beliefs, desires, and thoughts which have some sort of representational content - that is, they are about, directed at, mean, or represent something. So here, Searle is expressing the view that the simple formal simulating of a bunch of neurons firing cannot cause intentional mental states to be simulated. He is using causal in the traditional sense.
    – nwr
    Dec 14, 2021 at 1:37
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    "Causal properties" are those that allow the brain to interact with its environment, and hence establish connections between its structures ("intentional states") and what they are about (what's "intended"). Formal properties, on the other hand, are causally indifferent (which is why they can be detached and abstractly represented), and hence irrelevant to establishing intentional connections.
    – Conifold
    Dec 14, 2021 at 4:08
  • @Conifold So when I see a tree and associate it with the word "tree," is that what the causal property is? What differentiates from semantics?
    – Vasting
    Dec 14, 2021 at 4:14
  • The association mechanism involves causal properties (of the brain and body). "Semantics" is a very ambiguous word, formal semantics is of a kind with formal syntax, at best, it "relates" one abstraction to another, not to anything real.
    – Conifold
    Dec 14, 2021 at 4:55
  • Suggested tags.
    – J D
    Dec 14, 2021 at 11:31

3 Answers 3


Short Answer

John Searle accepts the human brain is a computer of sorts, but rejects that it is like current digital computers. He believes there's something inherently different between the biological causality of the brain with the universe and that of the digital computer with the universe, and so while both brains and computers have similarities, only brains can manifest "aboutness" (intentionality) about the state of affairs, he believes that physical causality is larger and different than the digital models, read Turing machines, we build of it. That difference is best understood as consciousness. He believes computers only dissimulate consciousness, which is the default position of many philosophers and can be traced back to Descartes and his views on the exceptional nature of the human mind. One particular view is that only humans have a soul, and not even animals truly reason. (See "Quotations from Descartes on Animals as Automata" (PhilSE).) Philosophical debate of Cartesian dualism is fundamental to an understanding of contemporary philosophy of mind.

Long Answer

Alan Turing once proposed his Turing Test and a timeline to show computers would quickly mimic the capacities of the brain. He would be profoundly disappointed that Hubert Dreyfus convincingly argued in his What Computers Can't Do: The Limits of Artificial Intelligence published in '72 that Turing was wrong. Searle is a relatively orthodox philosophical thinker who is skeptical that digital computers can ever fully represent the human brain and manifest consciousness, taken to be a necessary condition of intentionality. He is famous for his philosophical problem, the Chinese Room to advance his skepticism.

In his book The Mystery of Consciousness he says on 294:

[T]he essence of consciousness is that it consists in inner qualitative, subjective mental processes. You don't guarantee the duplication of those processes by duplicating the observable external behavioral effects of those processes.

This notion of computers possessing intentionality has even more challenge to it than overcoming radical solipsism where philosophers like David Chalmers have come up with philosophical ideas like philosophical zombies and the hard problem of consciousness to continue the tradition of the Ancient Greeks of making the fallibilism of knowledge evident through skeptical argumentation.

On the other end of the spectrum are more progressive thinkers like Alan Turing who believed in broad notions of artificial intelligence that might qualify him as a believer in artificial general intelligence which is a body of thinking that computers can be every bit as sentient and possess intentionality as people, broadly in the spirit of functionalism in the philosophy of mind. (Warning, my biases are with the AGI crowd: see See my response to Computers, Artificial Intelligence, and Epistemology). It's a matter of fact that a small but active community of cognitive scientists and philosophers are trying to advance a philosophical thesis to prove Searle wrong about how consciousness can be simulated.

As such, John Searle is largely in line with the orthodoxy in the broader analytic philosophical community expressing skepticism of the possibility that digital computers have or will ever have intentionality. Some interesting proposals have been advanced by thinkers who agree with Searle to come up with the missing part, Roger Penrose and his The Emperor's New Mind being an excellent example. In his thesis, there are quantum properties to neurons that are not represented by deterministic state machines that merely manifest computability.

Part of whether one believes Searle is wrong or not has to do with metaphysical presuppositions and first principles that are involved in the philosophy one does. Since computers are essentially composed of microprocessors ALU-CU-MMUs that compute formal systems, one's philosophy of mathematics can be used as a bellwether of sorts. For instance:

The association mechanism involves causal properties (of the brain and body). "Semantics" is a very ambiguous word, formal semantics is of a kind with formal syntax, at best, it "relates" one abstraction to another, not to anything real. - Conifold

It is arguable that formal semantics doesn't somehow relate to "real things", as every model-theoretic construction using the formalism of truth-conditional semantics is can be thought of as an abstract mathematical object used in the spirit of applied mathematics to model something real in the physical universe. Philosophically, mathematical constructivists see all formal systems including formal semantical models as rooted in the psychological experiences of the mind.

Whether or not it is possible to simulate a human brain is controversial in artificial intelligence, with one crowd believing that AI will never consist of anything more than symbolic systems and machine learning that will twiddle bits, and the AGI crowd believing that as soon as cognitive science provides insights that will allow machines to approach, attain, or even pass human intelligence, it will come to pass. The last position was made most famous by a futurist and computer scientist Ray Kurzweil who in transhumanism and the singularity as argued for in his The Singularity Is Near.

  • "As such, John Searle is largely in line with the orthodoxy in the broader analytic philosophical community expressing skepticism of the possibility that digital computers have or will ever have intentionality" What's the basis for saying this is position is the orthodox one? The SEP article on the Chinese Room lists many analytic philosophers who advocate the systems reply which says there would be consciousness/intentionality in the system as a whole, among them David Chalmers who is very influential in analytic philosophy of mind.
    – Hypnosifl
    Dec 14, 2021 at 19:54
  • @Hypnosfil Well, the question is an empirical one, so the anecdote of a list doesn't in anyway imply anything about a measure of central tendency pro and con.I certainly concede within the philosophy of mind, there's strong support that Searle's experiment is a failure. I have a while book devoted to replies of which my favorite is Haugeland's. I still if you take a broad cross-section of all self-described analytical philosophers, the predominant support for the physicalist paradigm prejuduces skepticism against, I suspect. But I concede my claim is speculative and anecdotal...
    – J D
    Dec 14, 2021 at 20:10
  • Of course Im open to any evidence to support a claim definitively one way or another. I live in a world of cyberpunk dreams and science fiction generally, but I don't know that the sort of optimism espoused by Ben Goetzel is supported by academia generally.
    – J D
    Dec 14, 2021 at 20:13
  • I suppose I should do my homework on the question.
    – J D
    Dec 14, 2021 at 20:13
  • the predominant support for the physicalist paradigm prejuduces skepticism against, I suspect By physicalist paradigm do you mean eliminative materialism about consciousness/intentionality (in which case the point would be somewhat trivial since these philosophers wouldn't believe either computer programs or human brains have the type of special 'intentionality' advocated by non eliminative materialists, i.e. they wouldn't say AI must lack something we have like Searle does), or something weaker like belief in the causal closure of the physical world (which Chalmers advocates as well)?
    – Hypnosifl
    Dec 14, 2021 at 20:51

I think that with causal properties Searle is referring to the brain's ability to cause physical actions by the muscles. Producing intentional states means configuring the motor cortex neurons in such way that they will send the intended control signals to the muscles.

This actually is something that a simulation cannot do. Simulations have no intentions, they don't intend to do anything. They only do what they are programmed to do, they only follow the programmer's intentions.

A computer program with intentions would no longer be a simulation. It would be a digital life-form.

  • +1 True indeed! (Except in the case of embodied simulations, like robots.)
    – J D
    Dec 14, 2021 at 14:42
  • What's the chain of causation here? Intentional states=> neurons => muscles. But what causes the intentional states in the first place? Dec 14, 2021 at 15:05
  • Intentional states are not caused. They are the first causes starting new causal chains of events. Dec 15, 2021 at 8:23

He is using “causal” in a conventional way, and “intentional” to refer to intentionality (https://plato.stanford.edu/entries/intentionality). He’s claiming that our primary interest in mental activity is not on the level of the brain’s formal structure or the behavior of its neurons and synapses, and that simulating these things doesn’t teach us anything about the brain’s ability to produce (i.e., cause) intentional states.

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