From the Not Even Wrong thread on Garrett Lisi's E8 theory: I had some questions in response to this; Woit complained (quite correctly) that my post didn't have anything to do with E8 or Woit's blog and requested the discussion not continue there. So I'm posting it here instead. My response to Marcus is: So while I personally find the no graviton approach attractive on several levels, it kind of seems like rejecting the graviton should be considered a dramatic step to take. Not bad-- just dramatic, so it should maybe be done carefully. Do there already exist any other theories of quantum gravity, besides Loll’s, which eschew the graviton or take the “graviton as approximation” approach you describe? Which ones? Does LQG, for example, have a graviton? Looking I am finding references to a “graviton propagator” in LQG but it is not immediately obvious whether that’s the same thing. ------ Aside from this I find Loll’s argument against the graviton in the paper Marcus links somewhat unconclusive by itself. “Well, we’ve been trying to get useful answers out of this construct for decades and haven’t succeeded, so it’s a good bet we’re doing something wrong” sounds like good strategy to me, but Loll doesn’t seem to actually be putting forth an argument about reality there, only an argument about “how to proceed”. I don’t see any reason that just because we can’t describe the graviton perturbatively, that would mean it doesn’t exist– since, as far as I understand, perturbation theory is supposed to just be an approximation anyway. (And this is of course assuming that perturbatively modeling the graviton is actually impossible, and not just too hard for anyone to manage right now!) Am I missing something about Loll’s argument?