[FOM] Putnam Replies

[Harvey Friedman]

Hilary Putnam has replied to my Replies to Putnam,  http://www.cs.nyu.edu/pipermail/fom/2009-June/013780.html

Hilary has given me permission to post his reply:

> Dear Harvey,
>    Thank you for the clarification, which I will save. It is very  
> nicely stated. Yes, we agree about the unjustified claims of some  
> category theorists. And your position is happily more nuanced than I  
> thought. I do think though that the realism-antirealism issue is one  
> of intrinsic intellectual interest. But even there we may not  
> disagree, because I think it does make a difference to systematic  
> knowledge in an indirect way. On that, I will forward a reply I gave  
> last year in Rome in a separate message.
>    Wonderful to see you and to meet your lovely wife and her nice  
> family.
>              Be well, and keep in touch,
>                    Hilary

Hilary sent me that "reply [he] gave last year in Rome", which I also  
present here with his permission:

I will reply to Hilary's reply to my reply to Hilary in a forthcoming  
posting to FOM.

> Reply to David Macarthur
>
> David Macarthur raises the question “Why do I want to keep the term  
> ‘metaphysics’?”. A general answer is that I am interested in  
> questions that are traditionally called “metaphysical questions”,  
> including a number that have arisen within science itself, and not  
> only within philosophy. I recognize that I have changed my position  
> since I wrote some of the statements that David quoted.) I think  
> that, for example,  the realism issue is important for science (I  
> argue this, for instance, in the paper “Science and Philosophy”— 
> forthcoming in a book of papers of mine edited by Mario De Caro and  
> David Macarthur).
>
> For example, whether one is a realist or an instrumentalist makes a  
> difference to the paradigm science of physics itself, and not only  
> to what philosophers say about physics. I think that when anti- 
> instrumentalism began to defeat logical positivism, and some  
> physicists—especially J.S. Bell—tried to understand physics  
> realistically, saying “We want to understand quantum mechanics not  
> just as a prediction tool, we want a picture of the world, we want  
> to make sense of a world in which this crazy tool works”, a great  
> many good things happened in physics that would not have happened  
> otherwise. Bell was interested in all the foundational approaches—he  
> was interested in Bohm’s interpretation, he was interested in GRW’s  
> (i.e. Ghirardi, Rimini and Weber’s) spontaneous collapse theory. I  
> don’t believe that the so-called “Many-Worlds interpretation” of  
> quantum mechanics works, but that  attempt did lead to the discovery  
> of the decoherence theorems which certainly are going to be part of  
> any explanation of why the macroscopic world we experience is as it  
> is, and that interpretation was proposed because its inventors, Hugh  
> Everett III, and  Cecil M. DeWitt were willing to take the question  
> as to what quantum mechancs actually says about reality seriously.  
> And the list goes on and on.
>
> Thus, if the question of realism and anti-realism is a metaphysical  
> question – and at least since Hume and Berkeley it has been a  
> metaphysical question (we did not have the modern kind of anti- 
> realism in the Greek time, but for sure that question has been with  
> us for three hundred years—there’s a straight line from Hume to  
> Mach, and  it entered physics itself with a vengeance)—then this  
> metaphysical question is one that cannot simply be dismissed as a  
> philosopher’s “confusions”, “misuse of language”, or whatever. And  
> if it isn’t a metaphysical question?—but I don’t know any other name  
> for that sort of question.
>
> In fact, the very philosophers who denounce metaphysics always get  
> entangled with it. Carnap had a metaphysical view of mathematics,  
> and it doesn’t work. (Here I disagree with my good friend, the late  
> Burton Dreben.) And I think that Wittgenstein himself was deeply in  
> the grip of a metaphysical picture—for example, when he claimed, as  
> he does, on my reading at least, that the only genuine kind of  
> necessity is linguistic necessity. I am afraid the great majority of  
> Wittgenstein’s unpublished remarks on the foundations of mathematics  
> are, frankly, junk,. (Not, however, the famous remark on Gödel  
> theorems – that’s been widely misunderstood.[i]) What finally led me  
> to this harsh verdict was studying his remarks about Dedekind cuts,  
> his remarks about Cantor’s proof of the non-denumerability of the  
> real numbers, and his remarks about what it means to say there are  
> infinitely many integers. When Wittgenstein says “I want to deprive  
> set theory of its charm”, one naturally thinks that what he wants to  
> give up is just Zermelo Fraenkel set theory. (Not that I would  
> agree, even if that were all he meant.)  In fact it turns out that  
> what he includes under “set theory” includes Dedekind cuts (hence  
> the intermediate value theorem of the calculus), includes the  
> standard treatment of the theory of real variables, includes the  
> heart of classical mathematics.
>
> How could a great philosopher, one who urged us constantly to be  
> sensitive to different “forms of life”, devote perhaps fifty percent  
> of his unpublished writing to mathematics, without ever seeking to  
> learn anything about what the mathematical form of life is? For  
> Wittgenstein Cantor’s Continuum Hypothesis is “metaphysics” in the  
> pejoritive sense! —But it seems to me that the metaphysical  
> questions; “What is going on in mathematics?”, “Is it really just  
> ‘’grammar?”, “Are we merely following certain linguistic rules and  
> engaging in certain linguistic practices?”, or “Is there an  
> objective truth in mathematics that goes outside of that?” (which is  
> my position), are important and rationally discussable. In my view,  
> whenever somebody sets out to be consistently “anti-metaphysical” he  
> ends up doing bad metaphysics. I believe this is true even of  
> Wittgenstein. This seems to be a very profound piece of evidence  
> that some metaphysical questions are inescapable.
>
> The realism question is one of those inescapable questions. And I  
> think also the question of fact and value is an inescapable  
> question. In America we think of Charles Stevenson as the one who  
> introduced the claim that value judgments can’t be rationally  
> decided, that they are out of the sphere of objective truth and  
> falsity, but it was raised earlier by the greatest of all European  
> sociologists, Max Weber. What is right and wrong about Weber’s fact- 
> value dichotomy is a question for all of the European cultures, and  
> ultimately for all of the world culture. Stevenson thought that the  
> question of fact and value could be simply disposed up, in the way  
> the logical positivists disposed of it. But he was wrong. Such   
> questions which are traditionally called “metaphysical” are  
> questions for which we have no other name. And they are going to  
> stay with us.
>
> To be sure, the way we cut up cultural space into separate fields  
> changes with time. It is well known that questions that were one  
> time considered to be philosophical questions later became  
> scientific questions. That doesn’t mean that all the questions we  
> presently call “philosophical” will eventually be swallowed up by  
> some special science. At least at present, that seems to me a  
> utopian fantasy. But the fact that it is no longer be tenable that  
> there exists a special field of metaphysics, doesn’t mean that  
> questions that were traditionally regarded as metaphysical don’t  
> continue to interest us. They interest us even when the  
> metaphysicians are wrong. For example, consider the premise of  
> Kant’s philosophy, the idea that the laws of geometry are a priori  
> and unrevisable and yet they refer to objective space, the space in  
> which we live and move and have our being, and not just to an “ideal  
> space”. I think he identified a real problem, but the fate of that  
> problem turned out to be very different then he anticipated.  
> Nevertheless, he asked the right questions. When I say there are  
> insights in traditional metaphysics, I mean precisely this.
>
> Hilary Putnam
>
> [i] See Juliet Floyd & Hilary Putnam (2000). ‘A Note on  
> Wittgenstein's "Notorious Paragraph" About the Gödel Theorem’.  
> Journal of Philosophy 97 (11), pp. 624-632.

Harvey Friedman