Re: Platonic Computation and OMs

From: Lee Corbin (
Date: Sun Apr 06 2008 - 10:24:51 MDT

Nick writes

> On Thu, Apr 3, 2008 at 2:22 AM, Lee Corbin <> wrote:
>> This has always seemed to me the weak spot in Putnam's
>> argument. Others too have commented that it is "unnatural"
>> to force any one thing to "isomorphically" line up with
>> another---it is as though the structure is being *added*
>> by whatever or whoever is "finding" such a relation, i.e.,
>> the isomorphism relation is not inherent in the structure
>> at the outset.
> What is "natural"? Why do you think your idea of "naturalness"
> corresponds to the laws of metaphysics?

It was, I admit, a poor choice of words; I put it in quotes
to try to diminish the extent to which I appeared to be
depending on it.

But is my main point clear? That is, I contend that some structures
exhibit actual isomorphism to other structures. (Such an assumption
is actually by definition in mathematics.) For one example, two "G2"
type stars really do have objectively more similarity to each other
than they do to a typical Volkswagen. Likewise, two Volkswagens
(of the same year and same make, especially) have intrinsically and
objectively more similarity of structure than either does with any
redwood. (It's possible that this claim separates the realists from
the nominalists, or from those of other philosophic schools, I really
don't know.)

Anyway, it would be possible, as Putnam has done (or so I understand)
to nonetheless *force* an isomorphism between a small rock and
any other possible computation. If we were to take a specific example,
then any given pebble in your garden can---under an isomorphism he
has detailed how to arrive at---be seen as performing the same
computation that an computer which has uploaded you is performing.
(Needless to say, this calls not only into question the very utility of
uploading, but even the utility of you preventing your body from
a deadly encounter with a truck tomorrow morning.)

In short, I think that you were correct to call into question any
(even intuitive) notion of "naturalness". I only wonder if the main
point which I was trying to make is nonetheless agreeable to


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