[FOM] The Lucas-Penrose Thesis

Muller F.A. F.A.Muller at phys.uu.nl
Wed Sep 27 02:01:22 EDT 2006

 Dear all,

 I have two brief questions, which I shall
 pose shortly, after the following introductory

 In 1961 the Oxford philosopher J.R. Lucas
 argued, roughly put (I know), that minds 
 cannot be (modelled as) machines due to Godel's
 Incompleteness Theorem. He repeated it,
 with some replies to criticisms, in his
 book *The Freedom of the Will* (1970).
 [Lucas has a personal website with more
 criticisms and responses, some of which
 are incontestably witty.]

 Among others, Hofstaedter discusses the
 'Lucas Thesis' in his celebrated *Godel,
 Esher, Bach* (1980).

 The thesis became famous when Roger Penrose
 propounded it in his best-seller *The
 Emperor's New Mind*. Hence the often used
 terminology `The Lucas-Penrose Thesis'.
 In a follow-up, *The Shadows of the Mind*,
 Penrose responds to critics. Rumour has it
 that he only responds to friendly criticisms,
 which leave the core of the cherished thesis 
 in tact, while he ignores devastating 
 criticisms, or only mentions them in order
 to ignore them. 

 I don't know. In Uppsala, Sweden, 1992
 (International Congress for Logic, Methodology
 and Philosoph of Science)
 I witnessed a discussion between Penrose 
 and D.C. Dennett on the Thesis; Dennett
 was critical but not really convincing. Penrose
 did not give an inch and seemed entirely
 undisturbed by anything critical that was
 brought up, by Dennett and others. I have heard
 (or read), on another occasion, Penrose making
 fun of the situation that everybody disagrees
 with him but the critics also disagree 
 among themselves about what is wrong with 
 the argument. 

 It doesn't seem that some simply
 fallacy is committed that once pointed
 out, ends the story.

 This reminds me of Einstein. The majority
 of the responses to his most cited paper,
 co-authored with Podolsky and Rosen on the
 (alleged) incompleteness of quantum mechanics
 (1935), was critical, but Einstein wrote in a 
 letter that all his critics disagree what exactly
 was wrong with his argument. There has been
 published a number of formalisations of the 
 EPR-argument, all transcending the bounds of
 1st-order classical logical, either by adding
 all sorts of ad hoc deduction-rules or by moving 
 to some modal logic. Some conclude that the EPR-
 argument is invalid, others that it is (or
 can be made) valid. Valid or not, it
 certainly is an interesting and influential

 Mutatis mutandis for the Lucas-Penrose
 Thesis? I am not saying that the situation with
 the Lucas-Penrose Thesis is wholly comparable.
 I only report this association to awake
 your interest. Here are my two brief questions.

 1. Is there any subscriber on the FOM-list
    who thinks the Lucas-Penrose Thesis is
    true or plausible or can be made true or

 I have the impression that most informed
 people think the thesis is false or 
 implausible or at least that its argument 
 is no good. Yet there a quite a few papers 
 published on the subject and they provide 
 different analyses.

 2. Can someone recommend a paper where it
    is established convincingly, once and 
    for all that the argument for the 
    Lucas-Penrose Thesis is no good, and
    sibling arguments also using Godel's
    Incompleteness Theorem to establish
    something similar are doomed?
 Much obliged,

 --> F.A. Muller

 Dr F.A. Muller
 Fac. Physics & Astronomy
 Utrecht University 
 f.a.muller at phys.uu.nl
 Fac. of Philosophy
 Erasmus University Rotterdam
 f.a.muller at fwb.eur.nl
 The Netherlands

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