Speaking as a devout Platonist I see nothing much to contemplate in Deutsch's statement! Whether the Universe is computable, as he states without argument, or the computable subrealm of the mathematical world coincides with the physical, which he believes for unstated reasons, is of no concern to me or any self-respecting Platonist. The Realm of Forms is entirely separate from the physical universe which is nothing but an inept and corrupt model of it. Our physical theories, and Deutsh's speculations are even crappier versions of that model which capture nothing but mere glimpses of the Platonic World and thus are destined to be surpassed.

Computation may be indeed a fairly acceptable measure of our ineptitude to see into Platonia: that is a plausible hypothesis. But the fact that we know of the realm of the uncomputable and that we can access its truths irrespective of our finite computational capabilities is an entirely more profound statement than any of Deutsch dubious speculations... -Joao Leao Lennart Nilsson wrote: > ----- Original Message ----- > From: "Lennart Nilsson" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Sunday, June 15, 2003 9:14 AM > Subject: Something for Platonists > > > Here is something from David Deutsch for Platonists to contemplate...I > think > > > > LN > > > > > > > > "We see around us a computable universe; that is to say, of all > > > > possible mathematical objects and relationships, only an in.nitesimal > > proportion > > > > are ever instantiated in the relationships of physical objects and > physical > > > > processes. (These are essentially the computable functions.) Now it might > > > > seem that one approach to explaining that amazing fact, is to say "the > > reason > > > > why physical processes conform to this very small part of mathematics, > > > > 'computable mathematics,' is that physical processes really are > computations > > > > running on a computer external to what we think of as physical reality." > But > > > > that relies on the assumption that the set of computable functions - the > > > > Turing computable functions, or the set of quantum computable operations > > > > - is somehow inherently privileged within mathematics. So that even a > > computer > > > > implemented in unknown physics (the supposed computer that we're > > > > all simulations on) would be expected to conform to those same notions of > > > > computability, to use those same functions that mathematics designates as > > > > computable. But in fact, the only thing that privileges the set of all > > computational > > > > operations that we see in nature, is that they are instantiated by > > > > the laws of physics. It is only through our knowledge of the physical > world > > > > that we know of the difference between computable and not computable. So > > > > it's only through our laws of physics that the nature of computation can > be > > > > understood. It can never be vice versa." > > > > -- Joao Pedro Leao ::: [EMAIL PROTECTED] Harvard-Smithsonian Center for Astrophysics 1815 Massachussetts Av. , Cambridge MA 02140 Work Phone: (617)-496-7990 extension 124 VoIP Phone: (617)=384-6679 Cell-Phone: (617)-817-1800 ---------------------------------------------- "All generalizations are abusive (specially this one!)" -------------------------------------------------------