Re: Turing machines and tape lenth

[Howard Pattee <***>]

Judith,

My post was intended only as a response to Tim who wrote:

> Rosen's concern with the formal
> aspects of modeling pertain to determining
> the limits of what a given formalism is capable of modeling. If one
> is
> trying to answer the question "why life?" and the answer
> involves models
> with closed loops of entailment, then answering such a question lies
> outside
> the limits of computable models.

HP: The question is why formal limits of computation should necessarily
carry over to emprically testable computer models. My examples show that
in general they do not. In any case, I think whether they do or not is
itself an empirical question. Tim asked the same question: 

Tim: Another way to say it would be: when do the inherent limits of
_expression_ in
formal models (in your first sense) impinge on the capacity for them to
be formal models (in your second sense)?

I have the impression that Rosen and Tim feel that in the case of
"closed loops of entailment" there is an a priori necessary
limit to empirical models. This is where I am not clear. Is a closed loop
of entailment a formal concept or can it only be empirically
recognized?

Howard