Re: modern physics

[Howard Pattee <***>]

Tim,
To keep the postings shorter and to the main points, I will not repeat everything.

I said in effect that measurement is an act of the observer who chooses what aspect of 
world he is interested in. That is the basic reason why laws cannot usefully describe the 
process of measurement (and why we must make an epistemic cut). In Rosen?s terms, coding 
(measurement) is unentailed by either causal natural laws or the inferential models.

Tim replies: First, I would argue, that in Rosen's view, the last sentence is incorrect.

HP: I would need some evidence of this. Rosen says (LI p. 61): "We can already see some 
peculiar epistemological issues inherent in the diagram of figure 3H.2 that did not arise 
earlier. Specifically: what is the status of the encoding and decoding arrows in that 
diagram? We already saw in the exactly similar diagram of figure 3F.2 that the encoding 
and decoding arrows were themselves unentailed. But at least they could themselves be 
considered as formal objects, since at that point we were comparing syntactric 
entailments of two formalisms. But now, we are comparing syntactic entailment in a 
formalism with causal entailment in a natural system. The encoding and decoding arrows in 
this case are still unentailed, but it is no longer clear how they could be entailed, or 
from what."

I have stated Rosen's view much more briefly, but I do not see how you can reasonably 
call my statement incorrect.

Tim: In the Modeling Relation, encoding and decoding are unentailed *within the MR 
itself*. However, they are not therefore unentailed entirely. Modeling Relations do occur 
within the world in which we believe physical laws operate.

HP: This is your statement, not Rosen's. Of course you are correct, but the physical 
entailments on the observer's choice of what to measure is very weak and exceptionally 
difficult to pin down. Rosen agrees that in practice the laws we discover are largely the 
result of what we choose to observe. One ultimately then has to face the issue of free 
will in making such a choice.

Tim: It is therefore incumbent upon physics to determine the laws appropriate to describe 
that physical situation and those entailments, not to except them from such laws.

HP: Measurement processes are certainly not exempt from laws. In principle, there is a 
lawful description (model) of any measurement. What von Neumann and others have shown is 
that such a description of a [system-plus-its-measurement-device] would require 
additional measurements leading to a vacuous regress. This can be explained in many ways. 
Measurement is inherently a complex process by Rosen's definition because it has a 
function (creating a record) that cannot be described by state-determined dynamics. A 
complex system, again by Rosen's definition, requires more than one inequivalent models. 
Inequivalent here means that neither model is reducible to, or derivable from, the other. 
In physics jargon this is what complementarity means. Consequently, laws and measurement 
require complemtary models.

I agree with everything Rosen says about the necessity of relational models. These are 
timeless, or synchronic models like symmetry. We also need dynamical diachronic models. 
These are complementary models. You cannot reduce one to the other or derive one from the 
other. Diachronic models bifurcate into time-symmetric (reversible microscopic laws) and 
the complementary time-antisymmetric models (irreversible thermodynamics). And so on. 
There are many cases.

What Rosen says about the limits of state-determined dynamics is certainly true. My only 
disagreement with Rosen is his view that physics limits itself to state-determined 
dynamics. That is just not the case.

Howard