That is,

1.  [**The decoupling of any nonmetric degrees of freedom**]{} from the dynamics of gravity implies that the gravitational effective action should depend on the metric alone.

2.  [**The methods of effective field theory**]{} then tell us how to formulate the action [@Burgess]. At the scales at which a metric description applies, the effective action will include all possible local, diffeomorphism-invariant functions of the metric that are not excluded by other symmetries. At low energies, this effective action will coincide with the Einstein-Hilbert action, albeit with a cosmological constant whose magnitude remains a mystery. One caveat remains: the derivative expansion that defines the effective action works only if the metric varies slowly compared to the Planck scale. This is certainly true observationally, but at a deeper level it is a further mystery.

These arguments do not require that the metric be a *fundamental* degree of freedom. Rather, they describe the setting in which an effective metric description might naturally emerge. On the one hand, this provides hope for emergent gravity: only a few steps are needed to obtain a model that agrees with observation. On the other hand, though, none of these steps can be avoided, and this places 