 According to the environment-induced approach to decoherence (Zurek 1981, 2003; see also Schlosshauer 2007), any macroscopic measuring apparatus is an open system in continuous interaction with its environment; as a consequence of this interaction, the reduced state of the apparatus becomes, almost instantaneously, indistinguishable from a state that would represent an ignorance mixture (“proper mixture”) over unknown but definite positions of the apparatus’ macroscopic pointer. The idea that decoherence might play an important role in modal interpretations, by making macroscopic quantities definite, was suggested by several authors early on (Dieks 1989, Healey 1995). Consideration of decoherence has acquired central relevance in the discussion of non-ideal measurements.