Feser's arguments against Computational Theories of Mind

Popper contra computationalism

The context makes it evident that Popper intends to make both a narrow point against any attempt to explain human rationality specifically on the model of the modern digital computer, and a more general but related point against any materialist attempt to explain rationality in causal terms.  It is with respect to the former point that we find a clear parallel with Searle.  In the passage quoted, Popper says that “practically all relevant properties of a computer qua computer… are not physical properties.”  This may seem odd given that he also allows that “the property of… a computer mechanism which makes it work according to the standards of logic is… in some sense connected with, or based upon, physical properties.”  But Popper also points out that the reason a computer operates according to logical principles is that it “has been designed by us – by human minds – to work like this” (p. 76).  Its operations mirror the semantic features of linguistic symbols and their logical relationships, just as the words written in ink on a piece of paper do; but the semantics and the logical relationships are no more inherent to the physical properties in the case of the computer than they are in the case of the ink marks.  In both cases they are imparted to the physical phenomena by us – by programmers and users in the case of computers, and by writers and readers in the case of written words – rather than derived from the physical phenomena.  Hence they can hardly provide a model of how rational thought processes might be explained in purely physical terms.

Searle’s version of this line of argument emphasizes that the key notions of the modern theory of computation – “symbol manipulation,” “syntactical rules,” “information processing,” and the like – are not definable in terms of the properties attributed to material systems by physical science, but are observer-relative, existing in a physical system only insofar as some interpreting mind attributes computational properties to it.  Hence the very idea that the mind might be explained in terms of computation is incoherent.  The argument can be summarized as follows:

1. Computation involves symbol manipulation according to syntactical rules.

2. But syntax and symbols are not definable in terms of the physics of a system.

3. So computation is not intrinsic to the physics of a system, but assigned to it by an observer.

4. So the brain cannot coherently be said to be intrinsically a digital computer.

(Searle develops this argument in his paper “Is the Brain a Digital Computer?” and in chapter 9 of his book The Rediscovery of the Mind.  Note that this argument is different from Searle’s better known “Chinese Room” argument.)

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Kripke contra computationalism 

In any actual machine, gears get stuck, components melt, and in myriad other ways the machine fails perfectly to instantiate the program we say it is running.  But there is nothing in the physical features or operations of the machine themselves that tells us that it has failed perfectly to instantiate its idealized program.  For relative to an eccentric program, even a machine with a stuck gear or melted component could be doing exactly what it is supposed to be doing, and a gear that doesn’t stick or a component that doesn’t melt could count as malfunctioning.  Hence there is nothing in the behavior of a computer, considered by itself, that can tell us whether its giving “125” in response to “What is 68 + 57?” counts as an instance of its following an idealized program for addition, or instead as a malfunction in a machine that is supposed to be carrying out an idealized program for quaddition.  And there is nothing in the behavior of a computer, considered by itself, that could tell us whether giving “5” in response to “What is 68 + 57?” counts as a malfunction in a machine that is supposed to be carrying out an idealized program for addition, or instead as an instance of properly following an idealized program for quaddition.

As Buechner points out, it is no good to appeal to counterfactuals to try to get around the problem -- to claim, for example, that what the machine would have done had it not malfunctioned is answer “125” rather than “5.”  For such a counterfactual presupposes that the idealized program the machine is instantiating is addition rather than quaddition, which is precisely what is in question. 

Naturally, we could always ask the programmer of the machine what he had in mind.  But that simply reinforces the point that there is nothing in the physical properties of the machine itself that can tell us.  But if there is nothing intrinsic to computers in general that determines what programs they are running, neither is there anything intrinsic to the human brain specifically, considered as a kind of computer, that determines what program it is running (if it is running one in the first place).  Hence there can be no question of explaining the human mind in terms of programs running in the brain.

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Accept no imitations

So, why might Turing or anyone else think that his proposed test casts any light on the question about whether machines can think?  There are at least three possible answers, and none of them is any good.  I’ll call them the Scholastic answer, the verificationist answer, and the scientistic answer.  Let’s consider each in turn.

Artificial intelligence and magical thinking

In an electronic computer, the inputs and outputs of a logic gate will take the form of electric currents, but in other sorts of machine they can take other forms, such as the positions of valves in a hydraulic computer, or the positions of sticks in a computer constructed out of Tinkertoy pieces.  There is nothing essentially electronic about a computer in the modern sense.  It’s just that an electronic computer is going to be vastly speedier and more efficient than a computer constructed out of materials of these other kinds.  In any case, all the complex activity that takes place in a computer of any sort will be an aggregate of the activities of basic elements such as logic gates.

It is easier to see the fallacy here if you think of a Tinkertoy computer or a hydraulic computer instead of an electronic computer.  It is obvious that the movements of sticks count as the implementation of logical functions, information processing, etc. only insofar as the designer has assigned such interpretations to the movements, and that apart from this interpretation they would be nothing more than meaningless movements.  No one is doing anything like that with the brain.  No one is saying “Let’s count this kind of neural process as an and-gate, that one as an or-gate, etc.” the way they are with the Tinkertoy sticks.  The reason people fall for the fallacy in the case of electronic computers is that they see an analogy between the computer’s electrical activity and the brain’s electrochemical activity and think it lends plausibility to the idea that the brain is a computer.  In reality the similarity is no more relevant than the fact that you can make a computer that weighs about as much as the brain, or one that is the same color as a brain.

I'm not convinced this particular argument, that electrical activity is equivalent to color/weight, is correct...also not sure an Idealist or Platonist can reject the idea of programs being conscious somehow...OTOH Feser is neither of those things...

Anyway here's the further reading he suggests:

Further reading:

Gödel and the mechanization of thought

Accept no imitations [on the Turing test]

Kripke contra computationalism

Do machines compute functions?

Can machines beg the question?

From Aristotle to John Searle and Back Again: Formal Causes, Teleology, and Computation in Nature [a 2016 article from the journal Nova et Vetera]

Kripke, Ross, and the Immaterial Aspects of Thought [a 2013 American Catholic Philosophical Quarterly article, reprinted in Neo-Scholastic Essays]

Kurzweil’s phantasms [a 2013 book review from First Things]