John M,
I agree. Re "part of [physicists'] philosophy is that if it can't be measured, it doesn't exist ":
There are things that can't be measured, but we can represent them either with words or symbols. E.g. I contend that physical reality is actually made out of not only things that can be measured, but things that can't be measured: the "+ - ÷ x" and the "=" found in law of nature mathematical equations represent non-measurable aspects of reality. These symbols can't just be swept under the carpet and ignored: if they don't live in a Platonic realm then they must represent a real part of THIS universe. (We might philosophise about what these symbols might imply about the nature of reality. I contend that they represent information relationship and information balance.)
Zeeya,
The non-measurable aspects of reality are the basis for a GENUINE alternative model of reality. There is nothing genuinely alternative about multiverses, living inside a computer game or loop quantum gravity etc. etc. because they are all just another set of equations with another set of interpretations of these equations: but they never examine what an equation actually is. Seemingly they all assume equations are given and non-decomposable; they turn a blind eye to the above mentioned non-measurable aspects of equations. Yet equations clearly consist of modular components, e.g. "+, -, ÷, x" and "=": so it is unlikely that what equations represent just arises whole and complete ex nihilo.
So I contend that unless a theory accounts for the "+ - ÷ x" and the "=" found in its equations, it is incomplete. It is a misrepresentation to propose e.g. a multiverse or a computer game universe: actually what is REALLY being hypothesised is a (multiverse PLUS platonic realm) or a (computer game universe PLUS platonic realm).
Cheers,
Lorraine