  Einstein considered general covariance to characterize the novelty of his
General Theory of Relativity (GTR), but Kretschmann thought it merely a formal
feature that any theory could have. The claim that GTR is "already
parametrized" suggests analyzing substantive general covariance as formal
general covariance achieved without hiding preferred coordinates as scalar
"clock fields," much as Einstein construed general covariance as the lack of
preferred coordinates. Physicists often install gauge symmetries artificially
with additional fields, as in the transition from Proca's to Stueckelberg's
electromagnetism. Some post-positivist philosophers, due to realist sympathies,
are committed to judging Stueckelberg's electromagnetism distinct from and
inferior to Proca's. By contrast, physicists identify them, the differences
being gauge-dependent and hence unreal. It is often useful to install gauge
freedom in theories with broken gauge symmetries (second-class constraints)
using a modified Batalin-Fradkin-Tyutin (BFT) procedure. Massive GTR, for which
parametrization and a Lagrangian BFT-like procedure appear to coincide, mimics
GTR's general covariance apart from telltale clock fields. A generalized
procedure for installing artificial gauge freedom subsumes parametrization and
BFT, while being more Lagrangian-friendly than BFT, leaving any primary
constraints unchanged and using a non-BFT boundary condition. Artificial gauge
freedom licenses a generalized Kretschmann objection. However, features of
paradigm cases of artificial gauge freedom might help to demonstrate a
principled distinction between substantive and merely formal gauge symmetry.
