Eric Hawthorne writes: > 2. SAS's which are part of a 3+1 space may not have higher measure than > SAS's in other spaces, but perhaps the SAS's > in the other spaces wouldn't have "a decent way to make a living". In > other words, maybe they'd have a hard time > perceiving the things in their space, existing coherently "physically" > in it, being able to "incrementally impact and survival-optimize" > their surroundings in the space etc. > In other words they'd be inhabiting (and trying to perceive and act on) > a world of NOISE, or of LIMITED DEGREES OF FREEDOM AND EVOLUTION, > or of UNRULY, untameable hyperbolic physical laws and functions.
I agree that this is what Tegmark is trying to say. If we look at it in terms of measure, there are (broadly speaking) two ways for creatures to exist: artificial or natural. By artificial I mean that there could be some incredibly complex combination of laws and initial conditions built into the simulated universe so that the creature's existence was in effect pre-ordained. (If we ever build a simulation containing conscious entities, our first attempts will almost certainly be of this type, where we have carefully crafted the program to create consciousness.) By natural I mean that we could have simple laws of physics and initial conditions in which the creatures evolve over a long period of time, as we have seen in our universe. Universes of the natural type would seem likely to have higher measure, because they are inherently simpler to specify. It is in those universes where Tegmark's physics-based arguments come into play. For creatures to evolve, to become complex, to optimize for survival, things like dimensionality are very relevant. Tegmark goes into some detail on the problems with other than 3+1 dimensional space. Of course, there's always a risk in such arguments that we may be falling victim to parochialism, thinking that our own way of life is the only one possible. It may be that there are some possible life forms that exist in a very different mode than we have imagined, in a universe with different dimensionality, or perhaps one where dimensionality doesn't even make sense. But I think overall Tegmark does a good job in avoiding at least the most obvious flaws of parochialism and anthropomorphism. Hal Finney