Hi Brent,

`----- Original Message -----`

`From: "Brent Meeker" <[EMAIL PROTECTED]>`

To: <everything-list@eskimo.com> Sent: Friday, July 22, 2005 8:31 PM Subject: Re: what relation do mathematical models have with reality?

On 22-Jul-05,Stephen P. King wrote:Hi Brent, Ok, I am rapidly loosing the connection that abstract models have with the physical world, at least in the case of computations. If there is no constraint on what we can conjecture, other than what is required by one's choice of logic and set theory, what relation do mathematical models have with reality? Is this not as obvious as it appears?[BM] Here's my $0.02. We can only base our knowledge on our experience and we don't experience *reality*, we just have certain experiences and we create a model that describes them and predicts them. Using this model to predict or describe usually involves some calculations and interpretation of the calculation in terms of the model. The relation of the model to reality, if it's a good one, is it gives us the right answer, i.e. it predicts accurately. Their are other criteria for a good model too, such as fitting in with other models we have; but prediction is the main standard. So in my view, mathematics and theorems about computer science are just models too, albeit more abstract ones. Persis Diaconsis says, "Statistics is just the physics of numbers." I have a similar view of all mathematics, e.g. arithmetic is just the physics of counting.

[SPK]

`Ok, I would agree completely with you if we are using Kant's definition`

`of *reality*- Dasein: existence in itself, but I was trying to be point out`

`that we must have some kind of connection between the abstract and the`

`concrete.`

`One thing that I hope we all can agree upon about *reality* is that what`

`ever it is, its properties are invariant with respect to transformations`

`from one point of view to any other. It is this trait that makes it`

`"independent", but the problems with realism seem to arise when we consider`

`whether or not this *reality* has some set of properties to the exclusion of`

`any others independent of some observational context.`

`QM demands that we not treat objects as having some sharp set of`

`properties independent of context and thus the main source of`

`counterintuitive aspects that make QM so difficult to deal with when we`

`approach the subject of Realism. OTOH, we have to come up with an`

`explanation of how it is that our individual experiences of a world seem to`

`be confined to sharp valuations and the appearance of property definiteness.`

`Everett and others gave us the solution to this conundrum with the MWI. Any`

`given object has eigenstates (?) that have eigenvalues (?) that are sharp`

`and definite relative to some other set of eigenstates, but as a whole a`

`state/wave function is a superposition of all possible.`

`So, what does this mean? We are to take the a priori and context`

`independent aspect of *reality* as not having any one set of sharp and`

`definite properties, it has a superposition of all possible. The trick is to`

`figure out a reason why we have one basis and not some other, one`

`partitioning of the eigenstates and not some other.`

`What does this have to do with mathematics and models? If we are going`

`to create/discover models of what we can all agree is sharp and definite-`

`our physical world, we must be sure that our models agree with each other.`

`This, of course, assumes that there is some connection between abstract and`

`concrete aspect of *reality*.`

Stephen