  A controversy that has arisen many times over in disparate contexts is
whether quantum coherences between eigenstates of certain quantities are fact
or fiction. We present a pedagogical introduction to the debate in the form of
a hypothetical dialogue between proponents from each of the two camps: a
factist and a fictionist. A resolution of the debate can be achieved, we argue,
by recognizing that quantum states do not only contain information about the
intrinsic properties of a system but about its extrinsic properties as well,
that is, about its relation to other systems external to it. Specifically, the
coherent quantum state of the factist is the appropriate description of the
relation of the system to one reference frame, while the incoherent quantum
state of the fictionist is the appropriate description of the relation of the
system to another, uncorrelated, reference frame. The two views, we conclude,
are alternative but equally valid paradigms of description.
