An interesting alternative is offered by Max Tegmark.
http://www.sns.ias.edu/~max/toe.html
or http://www.mpa-garching.mpg.de/~max/toe.html
He asks, why not say that all mathematical objects (or worlds) are physically
real? After all, if our models of physical reality are mathematical
models, what "extra something" is needed for something to be physically
real?
If all mathematical objects are physically real, then (he goes on to say)
we would expect to live in the simplest part of math capable of supporting,
well, scientists, basically. He says that there are testable
consequences of the hypothesis. He calls it a "Grand Ensemble" theory.
I love his illustration showing the superset-of links between various
realms of math, starting with Boolean algebra and leading up to General
Relativity and QM. With Felix the cat pondering the whole collection.
Also some interesting diagrams of the disasters that happen if you
tamper with certain physical constants by small amounts. NO SCIENTISTS
HERE (most of the diagram)! You are here (tiny little fenced-in area).
Righty-oh,
--Steve
-- sw@tiac.net Steve Witham web page under reconsideration "Philosophers have often attempted to analyze perception into the Given and what is then done with the Given by the mind. The Given is, of course, Taken..." --Daniel Dennett