  The spin-$j$ Einstein-Podolsky-Rosen experiment is studied with a view to
understanding how classical behaviour emerges as $j \to \infty$. It is proposed
that it is necessary to include detector error, which if it is be to viewed as
an essential aspect of the emergence of classicality, should be both minimal,
i.e., no more than necessary to wash out quantum mechanical behaviour, and
agnostic, by which is meant that one should be able to ascribe it to error in
the preparation of the state just as well as to the detector.Errors in the
state preparation are discussed via the spin Wigner function. An agnostic error
protocol is described which appears to be minimal.
