 Their idea is that when the fiducial measurement is a SIC, \(r(j\mathbin{|}i)\)) encodes the agent’s belief about the type of measurement \(M\), while \(p(i)\) encodes his or her quantum state for the system on which this measurement is performed. They maintain that the Born Rule in this form is an empirically motivated addition to probability theory—a normative requirement of quantum Bayesian coherence (Fuchs and Schack 2013; DeBrota, Fuchs, Pienaar, and Stacey, 2021) that supplements the usual coherence conditions on degrees of belief required to avoid a Dutch book (a set of bets an agent is guaranteed to lose, come what may).