how we should regard the size of some part of the configuration space compared to some other part, the L^2 norm is the blindingly obvious mathematical answer because of the properties of the wavefunction.
Does "part of the configuration space" refer to a single state vector, or a whole region that a state vector might belong to? My impression is that measuring the latter sort of thing is problematic from a rigorous mathematical standpoint. Is this correct, and does it have consequences for your discussion?
I say the former; people scared of continuous densities might prefer the latter, at which point they have the traditional sorites paradox of how large an epsilon-neighborhood to draw; but in practical terms, this isn't so bad because (if we start with low entropy) decoherence rapidly separates the wavefunction into thin wisps with almost-zero values taken between them.
These are extracts from some Facebook comments I made recently. I don't think they're actually understandable as is—they're definitely not formal and there isn't an actual underlying formalism I'm referring to, just commonly held intuitions. Or at least intuitions commonly held by me. Ahem. But anyway I figure it's worth a shot.
A proposal to
rationalizederive magick and miracles from updateless-like decision theoretic assumptions:(On Google+ I list my occupation as "Theoretical Thaumaturgist". ;P )