MINDS, MACHINES AND TURING: THE INDISTINGUISHABILITY OF INDISTINGUISHABLES Harnad, S. (2001) Minds, Machines and Turing: The Indistinguishability of Indistinguishables. Journal of Logic Language, and Information (special issue on "Alan Turing and Artificial Intelligence")

1. Intended Interpretation (the intentional fallacy)

2. The Standard Interpretation of Turing (1950) Turing is usually taken to be making a point about "thinking". Using the example of a party game in which one must guess which of two out-of-sight candidates is male and which is female on the basis of written messages alone (today we would say on the basis of -interaction alone), Turing asks what would happen if the two candidates were instead a man and a machine (let us say a digital computer, for the time being) and we could not tell them apart. For then it would follow that we could have no grounds for holding that one of them was thinking and the other was not. Hence either the question "What is thinking?" is meaningless, or it is provisionally answered by whatever proves successful in passing such a test.

3. Misinterpretations of Turing (1950) "Turing Test" would just be a trick: Turing "proved" that any candidate passing the TT must be thinking/intelligent.

4. Equivocation About Thinking and Machines "thinking" "real" "artificial" "natural" man-made "synthetic" "machine"

5. Functional Capacity: Mindful vs. Mindless 6. Turing Indistinguishability and the Other- Minds Problem 7. Out of Sight, Out of Mind: Dissociating Structure and Function 8. The Expressive Power of Natural Language and Formal Computation

9. The Turing Hierarchy: Level t1 (Toy Models) subtotal fragments of our functional capacity 10. Level T5 (Grand Unified Theories of Everything [GUTEs]) degrees of freedom of parts vs. wholes: scaling up

11. Utopian Differences That Make No Difference unobservable "quarks" or superstrings 12. Empirical Underdetermination and Turing Testing normal scientific underdetermination 13. Basic Science Vs. Engineering: Forward and Reverse

14. Level T2: The Pen-Pal Turing Test (Symbols- in/Symbols-out) Misunderstandings: Life-Long Symbolic/Nonsymbolic Man-Made Mindful Conscious Empirical/Intuitive

15. Searle's Chinese Room Argument (1) The mind is a computer program (computationalism) (2) The brain is irrelevant (implementation-independence) (3) The Turing Test is decisive (T2) T2 in Chinese, implemented by Searle.

Searle too makes a simple appeal to our intuitions, just as Turing did in appealing to the power of indistinguishability (i.e., if you can't tell them apart, you can't affirm of one what you deny of the other): Searle notes that, as the implementation is irrelevant, there is no reason he himself should not implement the code. So we are to suppose that Searle himself is executing all the computations on the input symbols in the Chinese messages -- all the algorithms and symbol manipulations -- that successfully generate the output symbols of the pen-pal's replies (the ones that are indistinguishable from those of real life-long pen-pals to real life- long pen-pals). Searle then simply points out to us that he would not be understanding the Chinese messages he was receiving and generating under these conditions (any more a student mindlessly going through the motions of executing some formal algorithm whose meaning he did not understand). Hence there is no reason to believe that the computer, implementing exactly the same code -- or indeed that anyimplementation of that code, merely in virtue of implementing that code -- would be understanding either.

16. Penetrating the Other-Minds Barrier Through Implementation-Independence 17. Multiple Minds? The Searlean Test [ST] "Searlean Test" (ST), be the candidate, execute the code oneself, and fail to experience the mental state (understanding) that is being attributed to the pen-pal. As one has no intuitive inclination whatsoever to impute extra mental states to oneself in the face of clear 1st-person evidence that one lacks them, the ST should, by the transitivity of implementation-independence, rule out all purely computational T2-passers. A purely computational T2-passer, in other words, is Turing- distinguishable from a candidate with a mind, and the way to make the distinction is to be the candidate, via the ST.

18. Grounding Symbols in Their Objects Rather than in the Mind of an External Interpreter 19. Level T3: The Robotic Turing Test 20. Level T4: Internal Microfunctional Indistinguishability

21. Grand Tournament of T-Levels: T3 vs. T4 vs. T5

Suppose that at the end of the day, when mind-modelling attains its Utopia, there are nine successful candidates. All nine are T3-indistinguishable from us, but three of them fail T4 (cut them open and they are clearly distinguishable in their internal microfunctions from us and our own real neural functions). Of the remaining six, three pass T4, but fail T5: their internal neural activities are functionally indistinguishable -- transplants can be swapped between us and them, at any biocomponential scale -- buttheirs are still crafted out of synthetic materials; they are T4- indistinguishable, but T5-distinguishable; only the last three are engineered out of real biological molecules, physically identical to our own, hence T5-indistinguishable from ourselves in every physical respect. The only remaining difference among these last three is that they were designed in collaboration with three different physicists, and each of the physicists happens to subscribe to a different GUTE -- of which there also happen to be three left at the end of the day.

So there we have our nine candidates: three T3's, three T4's and three T5's. All nine can correspond with you as a pen-pal for a lifetime; all nine can interact robotically with the people, objects, events and states in the world indistinguishably from you and me for a lifetime. All nine cry when you hurt them (whether physically or verbally), although three of them fail to bleed, and three of them bleed the wrong kind of blood. For the sake of argument, you have known all nine all your life (and consider them all close friends), and this state of affairs (that all nine are man-made) has only just been revealed to you today. You had never suspected it (across -- let us say, to calibrate our intuitions years of friendship and shared life experiences!). You are now being consulted as to which of the nine you feel can safely be deprived of their civil rights as a result of this new revelation. Which ones should it be, and why? [and T2?]

22. Level T3 Is Decisive 23. 1st-Person and 3rd-Person Facts 24. Quarks, Qualia, and Causality

25. Mind-Blindness, the Blind Watchmaker, and Mind over Matter telekinetic dualism Blind Watchmaker who forward-engineered us all (Darwinian Evolution) was a strict functionalist too, and likewise no mind- reader. Natural Selection is as incapable of distinguishing the Turing- indistinguishable as any of the rest of us.

26. Turing's Text and Turing's Mind This completes our exegesis of Turing (1950). Was this really the author's intended meaning? Perhaps not, but if not, then perhaps it ought to have been! His text is certainly systematically interpretable as meaning and implying all of this. But if Turing did not actually have it all in mind, then we are making a wrong pen-pal inference in imputing it to him -- and it should instead be attributed only to the inert code he generated in the form of his celebrated paper.

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