  The failure to calculate the vacuum energy is a central problem in
theoretical physics. Presumably the problem arises from the insistent use of
effective field theory reasoning in a context that is well beyond its intended
scope. If one follows this path, one is led inevitably to statistical or
anthropic reasoning for observations. It appears that a more palatable
resolution of the vacuum energy problem requires some form of UV/IR feedback.
In this paper we take the point of view that such feedback can be thought of as
arising by defining a notion of quantum space-time. We reformulate the
regularized computation of vacuum energy in such a way that it can be
interpreted in terms of a sum over elementary phase space volumes, that we
identify with a ground state degeneracy. This observation yields a precise
notion of UV/IR feedback, while leaving a scale unfixed. Here we argue that
holography can be thought to provide a key piece of information: we show that
equating this microscopic ground state degeneracy with macroscopic
gravitational entropy yields a prediction for the vacuum energy that can easily
be consistent with observations. Essentially, the smallness of the vacuum
energy is tied to the large size of the Universe. We discuss how within this
scenario notions of effective field theory can go so wrong.
