THE EXTERNAL REALITY HYPOTHESIS. Tegmark argues from the “external reality hypothesis”, which states that there exists an external physical reality completely independent of humans. This is a philosophical proposition that I agree with. Tegmark’s next step is to argue that “for a description to be complete, it must also be well-defined according to non-human entities – aliens or supercomputers, say – that lack any understanding of human concepts.” He gives the example of a basketball shot. Describing it with words like “basketball” or “sphere” would be to use words that humans have devised for their convenience and which would have no meaning for an alien. However describing the movement of each particle in the basketball would work for nonhumans. And something that can be described without human words that only have meanings for humans “is precisely a mathematical structure”. I have some difficulty with the step which goes from saying that everything in the universe can be described by math to saying that: “our universe isn’t just described by math, but that it is math….”
And, of course, I don’t really understand any of this.