Hi, I leafed through some of Rosen's stuff and the Kercel paper, I unfortunately do not have the time at the moment to work through it in detail, but some things which "disturb" me:
1) The assertion that the incomputable enters with "life". Rosen seems aware that he moves into the range of vitalism here, and tries to defend that he says it is not mechanism versus vitalism but simplicity versus complexity (=uncomputability in the Rosen sense) For my problems with his "uncomputability" see below. 2) Rosen repeatedly refers to Gödel's result and talks about how it shows how impoverished formalization are in regard to "real" mathematics. This of course leads to the question what "real" mathematics is. It seems that Rosen is Platonist (how else would he know what "real" mathematics is?), but this is an opinion one must not share. He also ignores that Gödel's results do not place limits on what one can formally model (in general), but only with regard to a formal system (finitely given, sufficient strenght etc). The question _if_ physics is completely formalizable/computable is indeed an interesting one, but why should this stage only start when life is concerned? (see below) Either it applies to the universe as a whole or it does not. 3) In the Kercel paper, we read: :START QUOTE: Given this, what does the (M,R)-system imply? In this model, the inferential entailments, the metabolism map f, the repair map F, and the replication map b represent the causal entailments in an organism, i.e., the efficient causes of metabolism, repair, and replication, respectively. If the (M,R)-system is actually in a modeling relation with the organism, then the same closed-loop hierarchical structure of containment of entailment must apply to the efficient causes. Just as map F contains map f contains in map b contains map F, ad infinitum, the efficient cause of repair contains the efficient cause of metabolism contains the efficient cause of replication contains the efficient cause of repair, ad infinitum. This is what it means to say that organisms contain the causal counterpart of impredicative loops. Rosen's expression "closed to efficient cause" now becomes clear. A real-world process is "closed to efficient cause" when it contains a closed-loop hierarchy of containment of efficient causes. Each efficient cause is contained by all the members of the loop that come before it, and contains all the members of the loop that come after it. :END QUOTE: What I fail to see that "life" embodies this "infinite" cycle as in his (M,R) system: after all, life started around 4 billion years ago - so I can _finitely_ list all cycles till some point where we are not interested anymore (depending on which theory of origin of life you prefer, rna first or metabolism first or whatever). 4) An ultrafinitistic view would generally rule out noncomputable models anyway (see for instance the nice essay by Doron Zeilberger: http://www.math.rutgers.edu/~zeilberg/mamarim/mamarimPDF/real.pdf) Or: http://en.wikipedia.org/wiki/Ultrafinitism So Rosen's model's also make some mathematical assumptions (which, admittedly, are widely shared - but may change, of course) 5) What I also find strange is the opposedness to computation: after all, with computers we are just beginning to find an "embarassment of riches"; fine to explore other avenues (Rosen), but I think it is much to early to dismiss the computational approach. So why his radical assertion that computational approaches to describe life must fail? 6) A point addressed in the Kercel paper: The ambiguity of language and the definiteness of computation: this is of import for the AI/Alife community, and it is indeed a problem, but is I think addressed if one can control the symbol grounding problem(Harnad, http://citeseer.ist.psu.edu/harnad90symbol.html). If one can let an AI/Alife really learn symbols (instead of programming them or assigning meaning to symbols by specification of the prog. language; the "learned" symbols would not make sense to us then, of course) they would inherently have the same ambiguity as our concepts have for us (because they would be learned in an ambiguous world). Conclusion: I think Rosen's ideas are valuable contributions in that they sensitivize us to certain problems, especially in modelling life. But the case against computatability is unconcinving. I would be very interested in thoughts of other FRIAMers, especially Glen who seems to have read a lot of Rosen's work - maybe you can clear up some things. Regards, Günther Glen E. P. Ropella wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Nicholas Thompson on 01/01/2008 10:59 PM: >> thus, to be a good formalism, a formalism has to be in >> some sense informal, right? > > This is a difficult question phrased in a misleadingly simple way. > > We now know that mathematics is _more_ than formal systems (thanks to > Goedel and those that have continued his work). I.e. we cannot > completely separate semantics from syntax. The semantic grounding of > any given formalism (regardless of how "obvious" the grounding is) > provides the hooks to the usage of the formalism. Hence, by the very > nature of math, any formalism can be traced back to the intentions for > the formalism (though the original intentions may be so densely > compressed or that uncompressing them may be hard or impossible). > > And in that sense, including your statement above, all formalisms will > then be good formalisms because they all have a semantic grounding. > > But just because all formalisms assume a semantic grounding doesn't mean > they're "informal". The hallmark of a formalism is that it encompasses > all the assumptions in axioms that are well-understood and clearly > stated up front. I.e. a good formalism won't let new axioms slip in > anytime during inference. So, that's what it now means to be "formal". > An informal inferential structure loosens that constraint and will > allow one to introduce new semantics as the inference chugs along. > > - -- > glen e. p. ropella, 971-219-3846, http://tempusdictum.com > It's too bad that stupidity isn't painful. -- Anton LaVey > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.6 (GNU/Linux) > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org > > iD8DBQFHe98oZeB+vOTnLkoRAjKfAJ0fFwhcKlZulDmkoXZaDKb3a/b76QCfXjC5 > WZaDT213cIPPOhP1bRH8rQE= > =cWA0 > -----END PGP SIGNATURE----- > > ============================================================ > FRIAM Applied Complexity Group listserv > Meets Fridays 9a-11:30 at cafe at St. John's College > lectures, archives, unsubscribe, maps at http://www.friam.org > -- Günther Greindl Department of Philosophy of Science University of Vienna [EMAIL PROTECTED] http://www.univie.ac.at/Wissenschaftstheorie/ Blog: http://dao.complexitystudies.org/ Site: http://www.complexitystudies.org ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org
