# Does a complete theory of quantum gravity require anthropic post-selection?

Does a complete theory of quantum gravity require anthropic post-selection? Certainly the black hole complimentarity and causal patch conjectures highlights the essential role of observers, at least in the asymptotic future of their future timelike trajectories. Does the measure problem in quantum gravity cosmology suggest that a "global god's eye view" of the universe might be an incoherent fiction? However, if observers are essential, don't we have to post-select to those states containing the observer of interest?

It might be suggested the S-matrix of string theory in a superselection sector with only a finite energy difference from the vacuum over a BPS background provides a counterexample, but can an asymptotic future state of noninteracting Fock space particles really support the future trajectory of an observer?

-
Anthropic? I don't think so. Probably experimental, that's it. –  Dimensio1n0 Aug 23 '13 at 19:51
It's fun to speculate about stuff like this, but I don't think it's realistic to imagine that anyone can say anything definite about characteristics of a theory of quantum gravity today. String theory and LQG both smell like failed research programs at this point. We don't even know what fundamental principles go into a theory of quantum gravity, e.g., whether it should be unitary or nonunitary. –  Ben Crowell Aug 23 '13 at 23:38
can an asymptotic future state of noninteracting Fock space particles really support the future trajectory of an observer? You need interactions to get an observer. For example, this is what stops us from having an observer made of massless, noninteracting particles all traveling along parallel geodesics -- which would be paradoxical, because you can't define a Lorentz boost for an observer moving at $c$. –  Ben Crowell Aug 23 '13 at 23:41