  The Hubble constant $H_0$ is the value of the cosmic expansion rate at one
time (the present), and cannot be adjusted successfully without taking into
account the entire expansion history and cosmology. We outline some conditions,
that if not quite ``no go'' are ``no thanks'', showing that changing the
expansion history, e.g. employing dynamical dark energy, cannot reconcile
disparate deductions of $H_0$ without upsetting some other cosmological
measurement.
