  The paper investigates the epistemic conception of quantum states---the view
that quantum states are not descriptions of quantum systems but rather reflect
the assigning agents' epistemic relations to the systems. This idea, which can
be found already in the works of Copenhagen adherents Heisenberg and Peierls,
has received increasing attention in recent years because it promises an
understanding of quantum theory in which neither the measurement problem nor a
conflict between quantum non-locality and relativity theory arises. Here it is
argued that the main challenge for proponents of this idea is to make sense of
the notion of a state assignment being performed correctly without thereby
acknowledging the notion of a true state of a quantum system---a state it is
in. An account based on the epistemic conception of states is proposed that
fulfills this requirement by interpreting the rules governing state assignment
as constitutive rules in the sense of John Searle.
